SYMPOSIUM E

11:00 AM *E1-S2.1 (invited)
Nanoparticles Doped with Rare Earth and Transition Metal Ions for Optoelectronic Applications. (#331) Marek Godlewski¹, Sergiy Yatsunenko¹, Agnieszka Opalinska², Janusz Fidelus², Witold Lojkowski²; ¹Institute of Physics Polish Academy of Sciences, Warsaw, Poland ; ²Institute of High Pressure Polish Academy of Sciences, Warsaw, Poland.

Incandescent lamps widely used for an overhead illumination are very inefficient and thus should be soon replaced by more efficient compact fluorescence lamps (CFLs) or white (GaN-based) light emitting diodes (w-LEDs). Both these modern light sources need efficient phosphors for light conversion from UV (in CFLs) or blue-violet (in w-LEDs) to a visible light. Most of phosphors used presently are based on wide band gap materials doped with rare earth (RE) or/and transition metal (TM) ions. Such doping helps to achieve light emission at required energy (color). Likely this trend will continue in future. In my presentation I will focus on perspectives of application as phosphors of nanometer size particles of wide band gap II-VI compounds and of ionic oxides doped with TM or RE ions. I will explain why nanometer size can be crucial to overcome some limitations in achieving high light output. For example, use of RE or TM ions as emission activators is often limited by inefficient intra-shell transitions of these ions, which are deactivated by parity and spin selection rules. I will demonstrate that these transitions can be efficient in doped nanoparticles, where they show much shorter luminescence decay times and brighter light emission. Mechanisms of emission stimulation in doped nanoparticles will be discussed. Further on, I will show that small size helps to enhance rate of energy transfer host-to-impurity, opening new efficient channels for RE/TM excitation. This effect also contributes to a brighter light emission. This work was partly supported by grant no. 1 P03B 090 30 of MNiSW granted for the years 2006-2008.

11:30 AM E1-S2.2
Photoluminescent Nanoparticle Surfaces. (#514) Oliver Diwald¹, Andreas Sternig¹, Markus Müller¹, Slavica Stankic², Johannes Bernardi³, Erich Knözinger¹; ¹Vienna University of Technology, Institute of Materials Chemistry, Austria ; ²Institut des Nanosciences de Paris, Campus de Boucicaut, CNRS, France ; ³Vienna University of Technology, USTEM, Austria.

Low coordinated sites on the surface of alkaline earth oxide particles absorb and emit light above λ>200 nm.[1] Since their enrichment and manipulation hold the key to produce nanocrystals with controlled optoelectronic and chemical activities, it is desirable to understand their structural and electronic properties and to identify their effect on the spectroscopic characteristics of an integral particle ensemble. With respect to particle size and morphology we observed profound differences between vacuum annealed MgO, CaO, SrO and BaO powder samples that were grown by chemical vapor deposition. With an average particle size of 6 nm MgO nanoparticles are single crystals with a well-defined cubic shape.[2] Much larger CaO (d ≈ 27 nm) and SrO (20 nm < d < 200 nm) particles are - due to temperature-induced coarsening and coalescence - morphologically much less defined.[3] A quantitative comparison of the optical absorption and photoluminescence emission properties of these three powders was carried out taking into account the difference in powder density and specific surface area. We found that aside from a systematic shift of excitation and emission bands into the range of visible light [1] there is also a substantial increase in the emission intensity going from MgO to SrO. Vacuum annealing of high surface area BaO powders induces the coalescence of unsupported BaO nanoparticles to compact millimeter sized grains which render the spectroscopic characterization of powdered materials impossible. However, the successful functionalization of MgO nanoparticle surfaces with BaO moieties gives rise to BaO specific changes in the surface electronic structure. The presented results will be discussed in terms of electronic and geometric surface structure and point to the fact that alkaline earth oxide powders are a promising class of nanomaterials with surface-dependent optical properties. In addition the availability of surface doping opens up an opportunity region for engineering the electronic surface structure of insulating nanocrystals that show potential as constituents of photoactive sensing devices and inorganic phosphors. References: [1] Spoto G.; Gribov E.N.; Ricchiardi G.; Damin A.; Scarano D.; Bordiga S.; Lamberti C.; Zecchina A.; Prog. Surf. Sci. 2004, 76, 71. [2] Stankic S.; Müller M.; Sterrer M.; Bernardi J.; Diwald O.; Knözinger E. Angew. Chem., Int. Ed. 2005, 44, 4917 [3] Stankic S.; Bernardi J.; Diwald O.; Knözinger E. J. Phys. Chem. C 2007, 111, 8069

11:45 AM E1-S2.3
An Analysis of the Dynamics of Excitation Exchange between Silicon Nanoclusters and Erbium Ions. (#120) Anthony Kenyon¹, Maciej Wojdak¹, Ijaz Ahmad¹, Wei Loh², Claudio Oton²; ¹Department Electronic & Electrical Engineering, University College London, United Kingdom ; ²University of Southampton, United Kingdom.

The sensitisation of erbium luminescence by silicon nanoclusters is a promising route to silicon-based optical sources and amplifiers. On studying the detailed photoluminescence dynamics of this coupled system, we find that the time evolution of photoluminescence cannot be described using a simple rate equation model. Both rise and fall times exhibit a stretched exponential behaviour, which we propose arises from a combination of a strongly distance-dependent silicon nanocluster-erbium interaction, along with the finite size distribution and indirect band gap of the silicon nanoclusters. We present a deconvolution of the stretched exponential to obtain the distribution of time constants in the experimental rise and fall data, and we suggest a physical interpretation of this in terms of the inhomogeneous nature of the material.

12:00 PM E1-S2.4
Electroluminescence from Colloidal Quantum Dot Light-Emitting Devices. (#481) Benjamin Scott Mashford, School of Chemistry, The University of Melbourne, Parkville, Victoria, Australia.

Thin film light-emitting devices (LEDs) that incorporate colloidal CdSe core-shell quantum dots (QD) into the emissive layer are currently being investigated via a variety of fabrication routes. QDs formed by chemical synthesis have been shown to yield QD materials with many desirable properties, such as a high luminescence quantum efficiency and a high degree of particle monodispersity. These properties may ultimately allow the manufacture of QD-LEDs with an emission wavelength that is both tuneable (by using QDs of the desired size) and with the high-quality spectral properties inherent to colloidal QDs. Although most recent reports of QD-LEDs include organic charge-transport layers, devices of this type have not yet overcome inherent problems of degradation from environmental oxygen and moisture. All-inorganic QD-LEDs have also been reported but the described fabrication procedures have involved high-vacuum conditions for deposition of the required charge-transport layers. We report here on successful demonstration of an all-inorganic QD-LED fabricated via inexpensive, wet-chemical techniques under ambient conditions. The use of sol-gel derived nanocrystalline metal-oxide transport layers combines the convenience of solution-route synthesis with the robust electrical properties of inorganic materials. Of key importance to device operation is control of the charge-transport properties of these nanocrystalline thin films. High levels of EL emission require a balanced rate of electron and hole injection into the QD active layer and this rate of charge injection in turn depends on energy band offsets and charge mobilities within the device. Optimisation of these parameters in our QD-LEDs has led to stable EL emissions with a spectral peak-position and linewidth that is nearly identical to that obtained in photoluminescence measurements. Detailed characterisations of the optical and electronic properties of these sol-gel derived materials are presented. These material properties are discussed in relation to understanding the EL process and to further improving device performance.

12:15 PM E1-S2.5
Electroluminescence in Silicon Nanocrystals Fabricated by Ion Beam Mixing and Annealing of Gate Oxide/Silicon Interfaces. (#393) K.-H. Heinig, B. Schmidt, V. Beyer, K.-H. Stegemann; Research Center Dresden-Rossendorf, Germany.

A light emitting field-effect transistor (LEFET) which is based on silicon nanocrystals in the gate oxide is demonstrated. The Si nanocrystals in the gate oxide were optimized for a multi-dot floating-gate nonvolatile memory operation [1]. For this aim, ion irradiation through the MOSFET stack of 50 nm poly-Si/15 nm SiO2/Si substrate was performed with 50 keV Si⁺ ions. The ion beam mixing of the upper poly-Si/SiO2 interface and the lower SiO2/(001)Si interface leads to Si excess in the gate oxide. Subsequent rapid thermal annealing reforms sharp interfaces and separates the excess Si from SiO2 [2]. Adjacent to the recovered interfaces, 3-4 nm thick SiO2 zones denuded completely of excess Si have been found, whereas the more distant tails of excess Si form well-aligned narrow layers of nanocrystals with 2-3 nm diameter. The electrical memory characteristics of the multi-dot floating-gate FETs have been published earlier [3]. Here we report on the fabrication and operation of such multi-dot floating-gate FETs as LEFETs. Our novel nanocluster fabrication leads to self-alignment of the nanoclusters in the gate oxide which allows a considerable improvement of LEFETs described recently [4]. LEFETs with an active gate area of 20x20 um2 were fabricated as nMOSFET devices in a standard 0.6 um CMOS process line. An AC voltage was applied to the gate in order to inject charges of both polarities into the lower and upper Si nanocrystal layer from the channel and the poly-Si gate of the transistor, respectively. AC voltage and frequency dependent electroluminescence spectra were recorded in the wavelength region of 400-1000 nm as a function of the annealing conditions. The performance of the LEFETs and further possibilities of optimization of efficient light emission will be discussed. [1] B. Schmidt, K.-H. Heinig, L. Roentzsch, T. Mueller, K.-H. Stegemann, E. Votintseva, Nucl. Instr. and Meth. B 242 (2006) 146. [2] K.-H. Heinig, T. Mueller, B. Schmidt, M. Strobel, W. Moeller, Appl. Phys. A77 (2003) 17. [3] P. Dimitrakis, P. Normand, E. Vontitseva, K.H. Stegemann, K.H. Heinig, B. Schmidt, J. Phys. C10 (2005) 7. [4] R. Walters, G.I. Bourianoff, H.A. Atwater, Nature Materials 4 (2005) 143.

LUNCH 12:30 PM - 2:00 PM

2:00 PM *E1-S3.1 (invited)
The Effect of Structural Order and Disorder on the Plasmon Absorption of Colloidal Crystals. (#444) Michael John Ford, Nadine Harris, Martin Blaber, Matthew Arnold, Michael B Cortie; Institute for Nanoscale Technology, University of Technology Sydney, Sydney, New South Wales, Australia.

Spherical nanoparticles of gold are the most ubiquitous of plasmonic structures, and have found potential or actual applications in areas as diverse as nanolithography or medical theurapeutics. The field has now moved beyond simple spheres; gold nanoparticles can now be synthesised in a variety of shapes including shells, rods, semi-shells, and core-shells. The use of novel materials, or combinations of materials, opens further possibilities for tuning the optical response or developing switchable devices. Aggregates of nanoparticles, such as colloidal crystals, provide a third dimension to the problem. We have already demonstrated a method for manufacturing micron-sized gold nanoparticle colloidal crystals directly from a gold colloid. These colloidal crystals are composed of very ordered arrays of 15 nm gold nanoparticles, and can be produced by laser irradiation of the colloidal suspension. T-matrix calculations of the optical response have been performed for these arrays of gold nanoparticles to investigate effects of order and disorder. For ordered arrays a second plasmon peak appears in the calculated extinction spectrum that is due to the long range order. For disordered arrays the extinction resembles that of a single particle having the same overall shape as the aggregate of particles. It is a simple matter to change the nanoparticle material in these calculations. Although gold is the most commonly used material its optical properties are not necessarily ideal. Although impractical from a chemical perspective, the alkali metals are optically superior. The use of simple alloys or intermetallic compounds offer an alternative approach for designing materials with a better balance of optical and chemical properties.

2:30 PM E1-S3.2
Raman Spectroscopy of Silicon Nanowires. (#1035) Paul Gregory Spizzirri, Steven Prawer; ARC Centre of Excellence for Quantum Computer Technology, School of Physics, The University of Melbourne, Parkville, Victoria, Australia.

Silicon nano-wires (much like carbon nano-tubes) have become candidates for alternative high density nano-electronics but may also find application in optical spectroscopy. As the wire dimensions reduce, they become 1 dimensional structures whose characteristics are quite different from that of the bulk material. For silicon, the bandgap can become direct and phonons away from the Brillouin-zone centre can participate in scattering processes making Raman spectroscopy an ideal tool for studying these systems. In addition, functionalisation of nano-wires with a metal particle on their tip may allow them to be used as nano-probes offering significant signal improvement in surface- or tip- enhanced nano-Raman measurements (i.e. SERS/TERS). In this work, we report on the fabrication and characterization of high quality silicon nano-wires with (and without) functionalized (metal) tips using Raman spectroscopy to study laser heating, phonon confinement and scattering cross section enhancements.

2:45 PM E1-S3.3
Platinum Nanoparticles for Thin Films and Devices; Control of Structure through Surfactant Selection. (#310) Sailaja Sivakamiammal Gopalakrishnanchettiar¹, Balagopal N Nair²; ¹Nanochemistry Research Institute, Department of Applied Chemistry, Curtin University of Technology, Perth, Western Australia, Australia ; ²Nanochemistry Research Institute, Department of Applied Chemistry, Curtin University of Technology, Perth, Western Australia and Noritake Company Ltd, Japan, Australia.

Platinum nanoparticles being the functional building blocks for many nanoelectronic devices, the scope of engineering their crystal morphology is extremely high. At the same time, developments in technologies to process and handle such platinum nanoparticles and their slurries at high yield are also important. Several wet chemical methods offer opportunities to directly process nanoparticle slurries with great process control and at high yields. In most scenarios, the properties of the organic surfactant employed in the process will influence the properties of the nanoparticles including their sizes and shapes. The selection of surfactants and solvents are therefore of great relevance. In the present study, platinum nanoparticles were synthesized by employing some of these concepts. We found that, the surfactant architecture has the primary role in determining the properties of the platinum nanoparticles. Nano-slurries with a platinum loading of >5 wt. % and a process yield higher than 95% could be achieved at room temperature by the suitable selection of surfactant. The sizes of platinum nanoparticles in the organic nano-slurries could be controlled easily in the range 1-10nm by controlling the processing parameters. These platinum nanoparticle slurries also possessed excellent film forming properties and therefore are potential candidates for several thin film applications including flexible electronic devices.

3:00 PM E1-S3.4
Bacterial S-Layer Templating Using Au Nanoparticles and Gene Modification . (#915) Susan Montgomery Graham¹, Andrew Ruys², Andrew Holmes², Anton Stampfl¹, Yeukuang Hwu³; ¹Bragg Institute, Australian Nuclear Science and Technology Organisation, Australia ; ²The University of Sydney, New South Wales, Australia ; ³National Synchrotron Radiation Research Centre, Taiwan.

X-ray bio-imaging and radiotherapy are currently converging disciplines that use nanoparticles as potential x-ray imaging/labelling and radiotherapy agents. One big problem for practical therapy is to find nanoparticle candidates that are inert and that will be transported directly and only to their target. In terms of imaging, the nanoparticle must have some property that will produce contrast. In the case of x-ray imaging, Au or Ag nanoparticles may be effectively used. Delivery systems can be of several forms: we are currently exploring the utility of S-layers as potential candidates not only as dumb units that deliver their load to some generalised target but as sophisticated functionalised units that will interrogate each target to determine the precise one. S-layers are interesting, highly ordered and crystalline surface layers that are produced by some species of bacteria and many archaea. S-layers mainly consist of a small number of glycoprotein sub-units which (when stripped off the cell) can self-assemble onto inorganic and organic solids (metal, semiconductor, polymer surfaces etc.), membranes, liquid-interfaces and simply in solution. S-layer lattices may have oblique, square or hexagonal symmetry, lattice spacings of 5-30 nm and thicknesses of 5-20 nm. S-layers are also rather sticky and so adsorption is strong. In this study we present x-ray microscopy results that show that Au and Ag nano-particles of only a few nanometers in diameter were effectively adsorbed on the surfaces of two bacteria, Lactobacillus brevis and Deinoccocus radiodurans. Preliminary results show that neither of these bacteria appeared to be affected by the presence of the nanoparticles on their surfaces. Stripped S-layers were also found to adsorb both the Au and Ag nanoparticles. In terms of electronic proprieties, as S-layers are so atomically regular we decided to investigate their detailed electronic structure using both whole bacteria fixed onto Si wafers as well as S-layers adsorbed onto Si(111) substrates. Photoemission spectroscopy and adsorption edge measurements are ideal techniques that directly probe electronic structure and are techniques that are extremely surface sensitive. Photoelectron spectroscopy of the core-level and valence band region as well as adsorption edge measurements were acquired at the Taiwan synchrotron, NSRRC and the Berlin synchrotron, BESSY, on fixed bacterial cells and on stripped S-layers with and without Au and Ag nanoparticles. Our results show amazing electronic details which indicate the supreme atomic regularity of our gold and silver nano-studded surfaces.

AFTERNOON BREAK 3:30 PM - 4:00 PM

4:00 PM E1-S4.1
Synthesis and Characterizations of Tapered SiGe Nanowires Array for Optoelectronic Applications. (#319) Hsi-Lien Hsiao, Zhi-Yong Chen; Department of Physics, Tunghai University, Taichung, Taiwan.

Nanostructures of different materials systems have been characterized for their field-emission properties. It has been reported that field emission from sponge-like Si nanowires demonstrates low-threshold and is comparable to that from various one-dimensional materials, including carbon nanotubes. Nevertheless, to fabricate a promising nanowires-based field emission display, the processing compatibility of nanowires array with present active matrix manufacture technology is a crucial step. In this report, we demonstrate successfully synthesis of tapered SiGe nanowires array onto gold pre-patterned Si substrates by chemical vapor synthetic approach at 380C and exhibit high degree of vertical alignment and high density. The bottom half of SiGe nanowires are estimated about 100 nm in diameter and the tip region is less than 10 nm. It is noted that the synthesized nanowires exhibit hexagonal shape cross section and smooth faceting surface. Vapor-liquid-solid synthetic reaction governing the axial growth and vapor-solid surface diffusion leading to the lateral epitaxial deposition, are believed to result in the formation of tapered nanostructures. The high crystalline quality depicted from SEM, TEM and Raman characterizations demonstrate potential applications of this low temperature selective growth techniques to large area flat panel display. The tapered SiGe nanowires exhibit a turn-on field of 5.8V/&mum and a threshold electric field of 8.8V/&mum. The excellent field emission characteristics are attributed to the tapered geometry of the crystalline SiGe nanowires.

4:15 PM E1-S4.2
Morphology and Photophysical Properties of Electrospun Light-Emitting Polystyrene/Poly(phenylene ethynylene) Nanofibers. (#1180) Sutheerat Changsarn¹, James D. Mendez², Michael Schroeter², Christoph Weder², Pitt Supaphol¹; ¹The Petroleum and Petrochemical College, Chulalongkorn University, Thailand ; ²Case Western Reserve University, Cleveland, Ohio, USA.

Nanofibers consisting of blends of a poly(2,5-dialkoxy-p-phenylene ethynylene) (PPE) derivative and poly(styrene) (PS) with average diameters ranging from 430 to 1200 nm were successfully produced by electrospinning solutions containing 7.5 % w/w PS and 1 % of the PPE in 1,2-dichloroethane or chloroform. The electrospinnability was significantly improved by adding a volatile organic salt, pyridinium formate, into the spinning solution. Fourier transform-infrared spectroscopy was used to confirm the chemical structure of the as-spun fibers. The photophysical properties of the as-prepared solutions, the as-spun fibers, annealed fibers, and solution-cast films were investigated by ultraviolet-visible absorption and photoluminescence (PL) spectroscopy. The PL emission study revealed a slight red shift in the emission spectra of the as-spun fibers compared to the spectra of the corresponding solutions. Spin-cast films and annealed nanofibers displayed a much more pronounced red-shift. The data suggest that aggregation of PPE molecules is prevented or significantly reduced by the spinning process and that the PS can act as a solid solvent for molecular mixtures. (Key-words:) electrospinning, photophysics, poly(phenylene ethynylene), photoluminescence * Author to whom correspondence should be addressed (E-mail address: pitt.s@chula.ac.th and christoph.weder@case.edu)

4:30 PM E1-S4.3
A Simple Synthesis of Hollow Carbon Microspheres. (#140) Bingshe Xu, Qiuping Luo, Yongzhen Yang, Chunyi Zhang, Xuguang Liu; Taiyuan University of Technology, Taiyuan, Shanxi, China.

Among various novel carbon nanomaterials, hollow carbon spheres (HCSs) have been attached much attention. When a metal catalyst is loaded in the shell of the HCSs, for instance, the well porous structure of HCSs can be an evident advantage for the reactive process, as a result of the much greater degree of the catalyst dispersion and an open network around the active catalyst for a facile diffusion of reactants and products. Herein, a new and very simple route is described for obtaining hollow carbon spheres (HCSs) by oxygenating the as-prepared solid carbon spheres (SCSs) at elevated temperature in air for several hours. The raw SCSs were prepared by chemical vapor deposition (CVD). The hollow spherical structures were observed by field emission scanning electron microscopy and high-resolution transmission electron microscopy. Raman spectrum and X-ray diffraction analysis were used to determine the crystal structures of HCSs. The possible formation mechanism of the HCSs was also discussed. Due to the simple process and low cost of this method, the mass production and potential applications of the HCSs will be promising.

4:45 PM E1-S4.4
Synthesis of Novel Standing SnO₂ Nanoslab Network and Its Application to NO₂ Sensing. (#368) Sunglyul Maeng, Sang-Woo Kim, Seung Eon Moon, Sang-Hyub Kim, Kang-Ho Park; IT Convergence & Components Laboratory, Electronics and Telecommunications Research Institute (ETRI), Yuseong-gu, Daejeon, Republic of Korea.

The novel SnO nanoslab network was synthesized on SiNx/Si substrate without catalyst at atmospheric pressure for the first time. The structure of a SnO nanoslab, formed at 500 oC by thermal evaporation in air, was identified as a tetragonal single crystal having no planar defects. The synthesized nanoslab network was further annealed at 700 oC for 1 hour in oxygen atmosphere to transform the unstable tetragonal SnO phase to stable rutile SnO2 phase. The result shows that the phase transformation from SnO to SnO2 occurred completely with some deformation which can be attributed to the strain caused by the phase transformation. The nanoslabs were crystallographically connected each other to form a network. This formation is ideal to be used as gas sensing element. In order to utilize the tin oxide 2-D network as NO2 sensor, SnO was first deposited onto the Pt interdigited electrode patterned on SiNx/Si substrate. Then, subsequent post-thermal annealing process was followed to complete the SnO2 nanoslab network sensor. The sensor was tested with various concentration of NO2 gas and much higher sensitivity was obtained comparing to the other SnO2 nanostructure-based NO2 sensors.

E1-S5.1
Preparation of Micro/nano Ni Material with the Shape of Microorganisms. (#105) Xin Liang, Jianhua Liu, Songmei Li, Mei Yu; Beihang University, HaiDian District, BeiJing, China.

The formation processes of a material were investigated by TEM based on the work of the pure Ni metal micro-rod material preparation by microbiological method and electroless deposition with the template of Nocadia. The growth of Nocadia was researched with different vibration rate (60rpm, 100rpm, 140rpm) and growth time. It is found that the growth of Nocadia composed of incubation period, fast growth period, stable growth period and decline period whatever the vibration rate is. The growth rate is the greatest when the vibration rate is 140rpm and the least in the case of 60rpm. However the length of Nocadia is the longest when the vibration rate is 60rpm and the shortest in the case of 140rpm. The optimal condition for growth is 100rpm with condition of length and growth rate of the bacteria. The formation processes include the dehydration of the interior bacteria and growth of outer pure Ni layer. With the Ni layer deposition the cytoplasm dehydrates due to high temperature in preparation processes. A pure Ni metal filamentous material with aspect ratio of higher than 80 was prepared with the same method. The material was characterized by SEM (scanning electron microscopy), EDS (energy dispersion spectroscopy) and TEM (transmission electron microscopy). The Ni layer composed of nano grains disperses uniformly along with the directions of diameter and length.

E1-S5.3
Structural and Electrical Studies of Tl (I) Substituted Tungesten HPOM. (#1198) Sambhaji Rajaram Mane¹, Popatrao N Bhosale²; ¹Department of Chemistry, KRP Kanya Mahavidyalaya,Islampur, District-Sangali, India ; ²Materials Research Laboratory, India.

Thallium (I) substituted tungsten heteropolyoxometalate (HPOM) combinatorial thin films have been deposited on glass substrate using simple chemical route. As deposited films were annealed at 50 oC, 100 oC, 250 oC and characterized by using SEM, EDAX and XRD techniques. Compositional analysis of as deposited and annealed thin films of Tl ( I) substituted tungsten heteropolyoxometalate (HPOM) were studied by EDAX and results reveled that as deposited and annealed thin films shows almost similar percentage of Tl. This shows that Tl (I) is intercalated in phosphotungustate anion. The lattice constant, crystallite size, and grain size were calculated. The lattice constant, crystallite size and grain size of tungsten HPOM material increases with increase in temperature. SEM images and XRD pattern of as deposited and annealed thin films shows nanocrystalline nature with simple cubic spinel structure. keywords: A. Nanocrystalline; B.Thin films; C.Annealing; D.HPOM.

E1-S5.4
Surface Atomic Structure of the Adsorption of Pt on Ge(001). (#1158) Gerardo Martinez, Pedro Hugo Hernandez, Gregorio Hernandez Cocoletzi; Instituto de Fisica, Universidad Autónoma de Puebla, Mexico.

We perform first principles total energy calculations to investigate the atomic structure of the adsorption of Pt on Ge(001) surfaces. Our studies are carried out using the periodic density functional. The exchange and correlation energies are treated according to the Perdew, Burke, Ernzerhof revised parameterization. The initial atomic structure is studied using molecular mechanics as implemented in the Forcite program of the Materials Studio(R) code. Afterwards we relax the atomic geometry using Castep. The reconstruction is in quasi-one dimensional structures. Results show the formation of nanowires on the Ge surface with periodicity b(2x1). These nanowires are composed of Pt dimers along the trenches between rows of Ge dimers. Our calculated STM images agree quite well with recent experimental results1. * This work was partially supported by a project of VIEP-BUAP. 1 Marinus Fisher, et al., Phys. Rev. B 76, 245429 (2007).

E1-S5.5
Some Features of Optical Properties Cadmium Sulfide Nanoparticles Generated in Volume of Polybutadiene Matrix. (#1215) Mustafa B. Muradov, A. M. Maharramov, G. M. Eyvazova, S. A. Talibova; Baku State University, Baku, Azerbaijan.

As is known cadmium sulfide nanoparticles are one of perspective materials for application in medicine as biomarkers , in creation of high-speed computing systems working in terahertz range. Successful Ion Layered Adsorption and Reaction (SILAR) is one of the perspective methods to receiving such particles in volume of the polymeric matrix[1]. In present work growth process and feature of optical properties CdS nanoparticles in volume of polybutadiene (PB) matrix is considered. For creation of the active centers which capable to sorb metal ions, ?? matrix subjected to chemical updating. Amount of sorption centers managed by change reaction duration. After that in volume ?? matrix have been generated CdS nanoparticles by SILAR. The received structures spectra of photoluminescence and UV-Vis was investigated. Results of researches have shown, that power spectra of photoluminescence does not depend on from degree of sorption centers and does not changes after thermal annealing at 85°C . It means, that thermal anneal does not influence to the sizes of particles. After thermal anneal intensity of photoluminescence from CdS in all samples decreases. It is connected with change of character interphase interaction in CdS: ?? nanocomposites. It is necessary to note, that thermal annealing miscellaneously influence on the intensity of photoluminescence cadmium sulfide nanoparticles, generated in volume ?? and gelatinous matrixes. After thermal anneal the photoluminescence intensity in CdS: ?? nanoparticles decreases, in system CdS:gelatin intensity increases. Thermal annealing reduces to increase of energy gap width [2] in samples CdS, but in CdS: ?? the band gap of CdS nanoparticles does not changed. The basic centers which are responsible for photoluminescence are related with interphase interaction between matrix and nanoparticles. Reduction of intensity photoluminescence after thermal anneal, apparently, is related with reduction of the centers responsible for photoluminescence. After thermal annealing was changed conformation of polymer molecules and character of interphase interaction between polymer and nanoparticles. References [1]. V.F.Nicolau, Appl. of surface Sci. 22/23 (1985) 1061. [2]. A.A.Agasiyev, M.B.Muradov, Pisma v Zurnal Technicheskoy Fiziki, 17 (1991) 54.

E1-S5.6
Elastic Behaviour and Internal Friction Studies on Nanocrystalline Mn-Zn Ferrite Films Prepared by the Method of Pulsed Laser Ablation. (#111) Sarabu Ramana Murhty, Materials Science and Nanophysics, Department of Physics, Osmania University, Hyderabad, India.

A laser ablation method was used for the preparation of nanocrystalline Mn-Zn ferrite thin films. Films were characterized using X-rays and TEM. The magnetic properties were measured using the vibrating sample magnetometer (VSM). The elastic behaviour and internal friction studies were carried out using composite piezoelectric oscillator method in the temperature range of 300-600 K. It was found that the value of Young's modulus decreases with an increase of temperature and shows anomalous behaviour in the vicinity of the Curie temperature. The internal friction for the present ferrites increases continuously with temperature up to the Curie point and a narrow peak was observed just below the Curie temperature. It was found that the anomalous behaviour observed in the temperature dependence of Young's modulus and internal friction disappears with the application of a magnetic field equal to the saturation field (900 mT) of the specimen under investigation. The observed anomalous behaviour in the vicinity of the Curie temperature was understood with the help of Landau's theory.

E1-S5.8
Synthesis and Preparation Optimization of Nano-Structured Al₂O₃. (#510) Mohammad Edrissi, Reza Norouzbeigi; Chemical Engineering Department, Amirkabir University, Tehran, Iran.

Nano-structured aluminum oxide powders were prepared by combustion synthesis method utilizing serine as a new fuel. The product was sonicated to obtain nano powders. A Taguchi L-4 statistical design of combustion synthesis was utilized to optimize the production of gamma-alumina powder. The product was characterized by XRD, BET, SEM, EDX, and LLS. Nano crystalline ?-alumina with crystal size between 4.2nm to 5.4nm and ?-alumina powders with crystal size 24.5nm and 28.6nm were obtained by combustion synthesis. The specific surface area was measured by BET method. Result shows 75.21m2/g. The average particle size after sonication of product, observed by LLS, was 79.3 nm.

E1-S5.9
Synthesis and Microporous Evaluation in Type A Zeolite (LTA) Exchanged with Inorganic Salts. (#954) Leobardo Corona Otero, Departamento de Investigación en Zeolitas, Universidad Autónoma de Puebla, Mexico.

In big cities atmospheric pollution problems are present in large scale and its effect on human health are not clear at all. These problems are related with global warming, vehicular traffic and the use of soils to name a few. To evaluate the external area of LTA zeolite, several techniques have been used. For instance, Hued et al. (Hued, 1986) uses the t method, while Carrot, Sing (Carrot, 1986) and (Hendricks, 1989) use the alpha-Sing method. The efficacy of these methods depends on a good election of a standard solid (Gregg, 1982). LTA zeolite was synthesised starting from Na [Al(OH)4] and Na2SiO3 a hydrogel mixture in stoichiometric amounts determined by crystallization field. An ion exchange in LTA zeolite with AgNO3, KCl, CaCl2, CdCl2, ZnCl2, CuCl2 and MnCl2 (0.1M for all of them) was carried out and then classified as: NaA, AgNaA, CaNaA, KNaA, CdNaA, ZnNaA and MnNaA. External area using the BET (Brunauer, 1945) and Langmuir (Gregg, 1967) equations in a range of p/po = 0.04 - 0.2 was calculated. The external area by using the t method (Lowell,1991) was obtained and the micropore volume (Wo) using (Alpha-Sing) method (Sing,1985) was calculated. Diffraction spectrums exhibit a typical spectrums for LTA zeolite. Characteristics obtained patterns correspond to those previously reported by Treacy et al. (Treacy, 1996). IR spectrum shows clearly the stretching of the bridge hydrogen between adsorbed water and the superficial oxygen (3400 - 3700 cm-1). Stretching in the plane Si-O-Si of the tetrahedral stage, generally shows a strong adsorption in the range of 970-1070 cm-1. In LTA zeolite case this adsorption is located approximately at 1000 cm-1. Adsorption isotherms belong to type I into IUPAC classification (Sing, 1985), this obligate to use the Langmuir method to evaluate them. Microporosity shows the presence of two kinds of micropores: ultramicropores (0.35 nm, approximatly) and supermicropores (1.8 nm) (Kaneko, 1994). Alpha-Sing graphics by using experimental values of a reference solid called alpha - quartz were obtained.

E1-S5.10
Spark Plasma Sintered Well-Aligned Carbon Nanotube Mat and its Electrical Anisotropy. (#137) Chunxu Pan, Xiang Qi; Department of Physics, Wuhan University, Hubei, China.

Carbon nanotubes (CNTs) have attracted great attentions due to their unique properties, such as electrical, thermal conductivity. Many effects have been made to study individual nanotube so as to explore the fundamental physical properties of CNTs. However, the measurements are extremely difficult due to its ultra small size and the results are scattering. Alternately, the physical properties of CNT mats have been used for evaluating an individual CNT. However, the random orientation of CNTs in the mad also influence results accuracy. In the present work, we successfully fabricated a well-aligned CNT mat by using a spark plasma sintering (SPS) system which provide a possibility to get a compacted bulk materials through hot pressing. Preliminary studies have shown that the CNT mat exhibited an anisotropic behavior. The regular CNTs synthesized from CVD were sintered in a SPS system with vacuum condition at temperature of 1773/1973 K for 5 minutes with uniaxial pressure (80 or 100Mpa). The heating rate is 100K/min. The sintering sample (CNT) mat was cut into cube with various sizes. The electrical conductivity and thermoelectric power (TEP) of the mat were measured from 60K to 290 K with vacuum condition. XRD, TEM and HRTEM results revealed that there were no changes after the SPS treatment. The fractured surface showed that the CNTs were well-aligned perpendicular to the uniaxial pressure, which should be resulted from the uniaxial pressure loaded in the sintering process. It was found that the electrical conductivity in the perpendicular direction was much larger than that in the parallel direction, that is, SPS treated and well-aligned CNTs mat was of an anisotropic behavior. In addition, the electrical conductivity was smaller than the theoretical result, which could be contributed to the intertube barrier. TEP has been considered as an indicator of the quality of nanotube alignment. In the present experiment, the TEP value was negative in the perpendicular direction to the unixial pressure. Therefore, we suggested that the CNTs have a high degree of alignment perpendicular to the pressure force, which was consistent with the SEM observations. This work is expecting to improve the exploration of CNT's fundamental physical properties.

E1-S5.11
Surface- and Volume-Related Excitation Mechanism of Eu-Doped GaN Nanocrystals. (#160) Artur Podhorodecki¹, Robert Kudrawiec¹, Marcin Nyk¹, Jan Misiewicz¹, Wiesław Stręk²; ¹Institute of Physics, Wroclaw University of Technology, Poland ; ²Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Poland.

Influence of the dopant position on the excitation mechanism of Eu3+ ions doped into nanocrystalline GaN powder has been investigated by using photoluminescence and photoluminescence excitation spectroscopy. It has been found, that depending on the grain sizes (surface to volume ratio in fact), different dopants excitation mechanisms can dominates. In the case of nanograins, it has been proposed that surface plays very important role and the dominant excitation of Eu3+ ions is via the local charge transfer from the oxygen atoms adsorbed post growth at the GaN nanocrystals surface.

E1-S5.12
Influence of the excitation energy on the recombination mechanism in silicon nanocrystals. (#158) Artur Podhorodecki¹, Jan Misiewicz¹, Fabrice Gourbilleau², Richard Rizk²; ¹Institute of Physics, Wroclaw University of Technology, Poland ; ²CIMAP, UMR CNRS, Poland.

In recent years, Si nanocrystals have received much attention as an emission source (electroluminescent diodes and lasers) for silicon-based optoelectronic applications. However, one of the most important problems of nanocrystalline materials remains the profound understanding of recombination mechanism in this kind of materials. Especially in the case of electroluminescence devices, where the recombination could become a complex process involving defects, phonons, tunneling etc. In this work, silicon-rich-silicon oxide films have been deposited by means of reactive magnetron sputtering at different hydrogen rate (rH =10-50%) to monitor Si nanocrystal size and the crystalline structure. To investigate the influence of rH on the recombination mechanisms, the emission spectra have been collected at different excitation powers and wavelengths, i.e. 302 nm (above the direct band gap of Si), 488 nm (above the indirect band gap of Si) and 532 nm which should be just below the indirect band gap of silicon nanocrystals versus temperature. As a result, depending on the excitation wavelength, strongly different temperature dependences of the emission intensity have been observed. Models have been used to analyze the data and to deduce the recombination parameters. It has been found, that all these parameters depend on the nanocrystals size and/or crystalline structure. Thus in this work, all these results will be presented and discussed in details.

E1-S5.13
Excitation Mechanism of Europium Ions Embedded into TiO₂ Nanocrystalline Thin Films. (#159) Artur Podhorodecki¹, Grzegorz Zatryb¹, Jan Misiewicz¹, Jarosław Domaradzki², Danuta Kaczmarek², Agnieszka Borkowska²; ¹Institute of Physics, Wroclaw University of Technology, Poland ; ²Faculty of Microsystem Electronics and Photonics, Wroclaw University of Technology, Poland.

In this work Eu3+ ions embedded into nanocrystalline TiO2 thin film were prepared by modified reactive magnetron sputtering. Excitation mechanism of europium ions has been investigated by photoluminescence spectroscopy and results were compared with different absorption-type experiments, i.e. absorption, photoluminescence excitation (PLE) and surface photovoltage spectroscopy (SPS). Complementary character of these techniques has been discussed from the point of view of europium excitation mechanisms. First of all, strong emission related to europium ions in the visible range has been observed and none emission related to TiO2 matrix, indicating efficient excitation transfer from the matrix to the ions at non resonant excitation. Second, based on obtained results, europium excitation mechanism has been confirmed and discussed.

E1-S5.14
Towards the Origin of Positive Magnetisation in Carbon Nanoclusters. (#433) Andrei V Rode¹, Denis Arcon², Nathan R. Madsen¹, Andrew G. Christy³, Barry Luther-Davies¹; ¹Laser Physics Centre, Research School of Physical Sciences and Engineering, The Australian National University, Australian Capital Territory, Australia ; ²Institute Jozef Stefan, Ljubljana, Slovenia ; ³Research School of Earth Sciences, The Australian National University, Australia.

Carbon nanoclusters produced by high-repetition-rate laser ablation of graphite and glassy carbon in Ar exhibits paramagnetic, superparamagnetic, and ferromagnetic behaviour. The results show that the degree of remanent order is strongly dependent on the magnetic history, i.e. whether the samples were cooled under zero-field or field conditions. Such behaviour is typical for a spin glass structure where the system can exist in many different roughly equivalent spin configurations. The spin-freezing temperature is unusually high (50 - 300 K) compared with <= 15 K for typical spin glasses. The maximum in the zero-field magnetic susceptibility experiments and their field dependence indicate that there is competition between ferromagnetic and antiferromagnetic exchange pathways, accounting for the spin glass behavior and/or a low-dimensionality of the system. Magnetic inhomogeneity is supported by detailed EPR studies, where we recognized three different types of centre with significantly different relaxation times, from very long one of the order of 1 ms, down to 100 ns. The results demonstrate the magnetically heterogeneous nature of carbon nanofoam with spin correlated magnetic clusters embedded in a non-spin correlated medium. The results show that carbon nanofoam is an inhomogeneous spin-glass like or superparamagnetic material with a high spin blocking temperature rather than a true homogeneous ferromagnet. These carbon nanoclusters may find biomedical applications such as target drug delivery, non-viral vectors for gene delivery, and as a contrast agent for in vivo Magnetic Resonance Imaging.

E1-S5.15
Super-Dense Materials Created by Laser-Induced Micro-Explosion. (#434) Andrei V Rode¹, Eugene G Gamaly¹, Wieslaw Z. Krolikowski¹, Barry Luther-Davies¹, Saulius Juodkazis², Hiroaki Misawa²; ¹Laser Physics Centre, Research School of Physical Sciences and Engineering, The Australian National University, Australian Capital Territory, Australia ; ²Hokkaido University, Sapporo, Japan.

Extremely high pressure (~10 TPa) and temperature (5x10^5 K) have been produced using a single laser pulse (100 nJ, 800 nm, 200 fs) focused inside transparent dielectrics. The laser pulse creates an intensity over 10^14 W/cm2 converting a material within the absorption volume of ~ 0.15 um3 into plasma in a few fs time. A pressure of ~10 Tpa, far exceeding the strength of any material, builds up to the end of the pulse generating strong shock and rarefaction waves. This results in the formation of a nano-void surrounded by a shell of shock-compressed material while the rest of the crystal remains undamaged. Analysis of the size of the void and the shock affected zone as a function of the deposited energy shows that the experimental results can be explicitly understood on the basis of conservation laws and be modeled by plasma hydrodynamics. In situ studies of compressed shell revealed that it has a density 1.14 times of the initial one and increased reactivity. High-density sapphire completely dissolves in 10% solution of hydrofluoric acid while pristine sapphire remains intact. The unique conditions created in such an inter-action - pressure of 10 TPa, temperature of 5x10^5K, record high heating rate of 10^18 Kelvin/s and and cooling rate 10^15 Kelvin/s open an exciting research field in condense matter physics for studying matter at extreme in well-controlled laboratory environment.

E1-S5.16
Influence of Curvature of Graphene Layers on Electron-Electron Interaction in Multiwalled Carbon Nanotubes. (#79) Anatoly Ivanovich Romanenko¹, Vladimir Lvovich Kuznetsov², Olga Borisovna Anikeeva³, Timofey Igorevich Buryakov³, Evgeniy Nikolaevich Tkachev³, Kamil Ravilevich Zhdanov³, Anna Nikolaevna Usoltseva²; ¹Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Science, Novosibirsk, Russian Federation ; ²Boreskov Institute of Catalisis, Novosibirsk State University, Russian Federation ; ³Nikolaev Institute of Inorganic Chemistry, Novosibirsk State University, Russian Federation.

We investigated dependences of conductivity from temperature and magnetic field of multiwalled carbon nanotubes. We separated the quantum corrections to magnetoresistivity for interaction electrons and estimated the dependence of constant of electron-electron interaction from curvature of graphene layers in multiwalled carbon nanotubes. Multiwalled carbon nanotubes were produced via CVD method using C2H4 decomposition at 920-1070 K. Variation of catalysts composition and reaction conditions allows to produce MWNTs with controllable and relatively narrow diameter distribution. The dependences of the conductivity from temperature and magnetic field were measured by four-point-probe technique in the temperature range 4.2-300 K and in the magnetic field up to 6 T. We discovered that in multiwalled carbon nanotubes produced via our CVD method is absent another phase of carbon. As a result in quantum corrections to magnetoresistivity take place only quantum corrections for interaction electrons without any quantum corrections for weak localization effects. From the data of quantum corrections to magnetoresistivity for interaction electrons we estimated the constant of electron-electron interaction. This constant is positive (repulsion between electrons) and monotonically decrease with decreases of average diameter of multiwalled carbon nanotubes (increase of curvature of graphene layers). In multiwalled carbon nanotubes with average diameter less then 6 nm the constant of electron-electron interaction becomes negative. This result is in a good agreement with experimental observation of superconducting state in nanotubes with diameter 1 nm at temperature 1 K and with diameter 0.4 nm at temperature 20 K.

E1-S5.17
Hybrid Polymer Solar Cells: How Colloid Science Could Bring Deployment Closer. (#1298) Brian Roy Saunders, School of Materials, The University of Manchester, United Kingdom.

The need to develop and deploy large-scale, cost-effective, renewable energy is becoming increasingly important. Even though silicon solar cells have high power conversion efficiencies (PCE) they are expensive to produce and have long energy payback times. A cost reduction in solar derived electricity of about an order of magnitude is required to enable widespread deployment. This requires an alternative type of solar cell prepared using wet-processing techniques. In recent years hybrid polymer solar cells containing inorganic nanoparticles (e.g., CdSe, ZnO or PbS) blended with semiconducting polymers have been investigated. These solar cells offer great promise because both components can in principle harvest light. The highest PCE values reported for these solar cells to date is[1] 2.8%. PCE values of at least 10 % are required in order for commercialisation to be viable. One important problem restricting the PCE for hybrid polymer solar cells is colloidal in nature. The photoactive layers for these solar cells are prepared using a three component blend of inorganic nanoparticles, conjugated polymer and organic solvent[2]. Solvent evaporation during film formation results extensive phase separation. This results in polymer-rich domains between nanoparticle aggregates within the photoactive layer. These regions cause recombination of the photogenerated charge carriers and decrease the PCE. The ideal photoactive layer would consist of strings of touching, naked, nanoparticles with an average inter-string separation of about 10 nm. The polymer and nanoparticle phases would be bicontinuous. Even though there are a number of colloidal factors that favour nanoparticle aggregation and phase separation during film formation there are others that could be used to prevent this. This presentation aims to show how colloid and interface science could enable major improvements of the PCEs for hybrid polymer solar cells. Recent results obtained from our lab are presented to support the discussion. [1] B. Sun, H. J. Snaith, A. Dhoot, S. Westenhoff and N. C. Greenham, J. Appl. Phys. 2005, 97, 014914. [2] B. R. Saunders and M. Turner, Adv. Coll. Interf. Sci. 2008, 138, 1.

E1-S5.18
Preparation of TiO₂ Nanorods for Improving Electron Transport of Dye Sensitized Solar Cells. (#1031) Sang Il Seok, In Chan Baek, Jeong A Chang, Jae-Yeol Hwang; Korea Research Institute of Chemical Technology, Republic of Korea.

Dye-sensitized solar cells (DSSC) based on nanocrystalline mesoporous TiO2 films have been widely investigated due to the expectation of high energy conversion efficiency and low cost. Recent efforts for a high efficient DSSC have been being focused on the development of new sensitizer of narrow bandgap to utilize broader solar spectrum, and the optimization of the system by altering the particle size and morphology of TiO2. Among the several key factors, the insufficient electron transport in highly porous TiO2 electrodes with spherical nanoparticles is believed to limit the overall efficiency of DSSC. At this point, it will be one of alternatives to use TiO2 photoanodes of long rod shapes with the decreased grain boundaries to enhance an electron transport. We successfully synthesized highly crystalline TiO2 nanorods with lengths of 150-250 nm and diameters of 20-30 nm via hydrothermal treatment of titanium peroxide solution, produced by reaction of H2O2 and titanium hydrate gel, without adding any surfactant. TiO2 nanorods as prepared show a pure highly crystalline anatase phase by X-ray diffraction. The DSSC fabricated from nanorods exhibited higher solar energy conversion efficiency compared to P25 (a typical commercially available TiO2) cells

E1-S5.19
Nano Structured Nanoparticle Array for Bio Sensing. (#1046) Hiroshi Shiigi, Itaru Ota, Shiho Tokonami, Tsutomu Nagaoka; Frontier Science Innovation Center, Osaka Prefecture University, Sakai, Japan.

We have developed a novel label-free technique based on a resistance change of gold nanoparticles (AuNPs) array due to a change of an opening bridge structure by hybridization. The resistance change by the hybridization event can be directly detected with a resolution as high as that allowing the detection of single nucleotide polymorphism. The sensor responded over a wide concentration range with 5.0 fmol of the detection limit. DNA hybridization occurred certainly between particles, therefore, the conductivity change can be explained not only by the molecular conductivity of DNA but also by the shrinkage of the structural distance of the 12 nm probes in the gap of the 50-nm parent particles by hybridization. To see if this system works for the discrimination of mismatches, we carried out experiments using targeted DNA with complementary, 1-bp, 2-bp, and 24-bp mismatched (fully mismatched) sequences. The results for the poly(T)-poly(A) hybridization, indicate that the response was the highest for the complementary DNA and decreased with an increase in the number of mismatched bases. Finally, the change in the resistance was hardly observed at fully mismatched sequence. Furthermore, the response for each target sequence was almost constant, even if the series of measurements were performed from complementary or fully mismatched sequence. In the series of experiments repeated with hybridizing and denaturing, the response for the complementary strand measured was stable. The response behaved in a non-linear fashion with respect to the number of mismatches, and the clear difference found between the complementary and 1 bp mismatch suggests that this system would be used for the SNP diagnosis in a highly efficient manner. A similar trend for the mismatch detection for randomly sequenced fragments suggests that this method could be used for practical DNA identification. In summary, we have constructed a highly-sensitive label-free opening-bridge structure based DNA detection system from a nano-gapped gold nanoparticle array. Creating a conducting path with a 12-nm gold nanoparticle probes bridged between 50 nm gold nanoparticles by a hybridization event produced a response with the detection limit of 5.0 fmol. This simple system allowed us to discriminate complemenary and single base pair mismatches.

E1-S5.20
Simple Preparation of Positively Charged Nanoarchitecture. (#1069) Hiroshi Shiigi, Ryosuke Morita, Yojiro Yamamoto, Tsutomu Nagaoka; Osaka Prefecture University, Sakai, Japan.

Metal nanoparticles are of fundamental interest to many researchers because of their controllable grain diameter and their potential applications in emerging areas of nanotechnology due to their unique electronic and optical properties. Their distinguishing shapes and combinations, such as nanobarcodes, nanorods, and nanowires produce unique functions along with the rare functions of bulk metals. A building up of structures in a particle-by-particle fashion simultaneously organizes many particles into self-assembled materials with the requirement of easily controlling the chemical reactivity and interparticle connectivity on a single-particle level. We present a simple preparation method of positively charged-AuNPs with a one step-processing without an extra controlled procedure, organic solvents, and ligand exchange. Moreover, AuNP has an interesting raspberry like-configuration as a buliding-block of the nanoarchitecture. A novel positively-charged AuNP was prepared using a reducer such as aniline. The simple preparative procedure was as follows. An aqueous aniline solution was added to a chloroauric acid aqueous solution, and stirred. The resulting solution was then centrifuged. The first-supernatant was removed. The precipitate was again redispersed in ultrapure water, and then the dispersion was centrifuged using the same conditions described above. TEM image represented a raspberry-like aggregation of AuNP was formed that possessed a 1.5 nm-mean particle diameter . The aggregation, consisting of the aurum element determined by elemental analysis, was covered by a misty passivation layer (4.0 nm). The UV spectral analysis followed the time course of the preparation process of the AuNP. The mixture solution of aurate and aniline was allowed to stand with stirring at 338 K. During the first stage, the orange-pink colored mixture solution had an absorption at 485 nm, which was attributed to the original color of the respective component and surface plasmon resonance. While a gradual red shift in the peak intensity to 553 nm was observed, a new peak at 700 nm occurred and increased after 20 min. This means that the aurate was reduced to aurum by the aniline, while aniline was oxidized to an oligomer by the aurate along with the rising temperature. The electrical property of aniline-AuNP significantly changed after the acid doping and dedoping. The doped aniline-AuNP revealed the good conducting property. This is similar to the conductivity of the generally reported salt-type polyaniline. On the contrary, the electrical conductivity of the base-type aniline-AuNP had a dramatically reduced. In summary, we developed a facile one step-processing without an extra controlled procedure, organic solvents, and ligand exchange, which allows us to obtain a positively charged-AuNP of which the raspberry-aggregation was on a nanoorder level. It is expected that AuNPs prepared by aniline strongly interacted with biomolecules containing carboxylate and phosphate groups. Therefore, this method will also be helpful for investigating and constructing metal nanoparticles, a biomolecule composite and organic polymer materials.

E1-S5.21
Carboxylate Anions Can Facilitate Radiation-Induced Silver Nanoparticle Formation. (#30) Junhwa Shin, Yunhye Kim, Youn Mook Lim, Young Chang Nho; Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Republic of Korea.

Nano-sized metallic materials are of great interest because they can exhibit extraordinary electrical and optical properties which are distinctly different from those of a bulk. Many synthetic methods have been developed for the preparation of nanoparticles and utilized in a wide range of applications. Since nanoparticles are likely to coalesce to form larger particle clusters during nanoparticle formation, an appropriate nanoparticle stabilizer such as PVA, PVP, PAA, and PGA etc should be added to prevent a coalescence of the nanoparticles. Several silver nanoparticles (AgNPs) were prepared in PVA solution containing various amounts of NaOAc by γ-ray irradiation using 60Co source at various doses. The UV data of the AgNPs observed at around 410 nm shows that more AgNPs are generally produced as the NaOAc concentration in the PVA solution increases. No significant absorption band of the AgNPs was observed when the purified PVA was applied at a dose of 10 kGy. These results indicate that NaOAc (a carboxylate impurity present in PVA) plays an important role in the radiolytic formation of AgNPs. The effects of other carboxylates such as sodium citrate and poly(acrylic acid) were also studied on the radiolytic formation of AgNPs in PVA and other polymer stabilizers. These results indicate that carboxylate anions can facilitate radiation-induced silver nanoparticle.

E1-S5.22
Synthesis and Structural Analysis of Nanocrystalline Nd³⁺ Substituted Zinc Ferrites. (#1156) Tukaram Jaysing Shinde¹, Ashok B Gadkari², Pramod N Vasambekar³; ¹Department of Physics, K.R.P. Kanya Mahavidyalaya, Islampur, Sangli, Maharashtra, India ; ²G.K.G. College Kolhapur, India ; ³Department of Electronics, Shivaji University, India.

Abstract Compositions having general formula ZnNdyFe2-yO4 (where y = 0, 0.01, 0.02 and 0.03) were synthesized by oxalate co-precipitation method. X-ray diffraction, Infrared absorption spectroscopy and Scanning electron microscopy were used to characterize the compositions. The single phase cubic spinel structure of the compositions was confirmed by XRD. Lattice constant was found to be decrease with increasing Nd3+ concentration. X-ray density increases with increasing Nd3+ content. The crystallite size of the samples lies in the range 29.74nm to 31.46nm. Infrared spectra show three absorption bands within the range of 400cm-1 to 700cm-1 and analysis shows that Nd3+ occupies B-site. SEM study shows that average grain size of the samples lies in the range 0.5826?m to 0.3823 ?m Keyword: Ferrites, Nanomaterials, XRD, IR, SEM.

E1-S5.24
Abnormal Transmittance of Refractive-Index Modified ZnO - Organic Hybrid Films. (#64) Tak Tsuzuki, Centre for Material and Fibre Innovation, Deakin University, Victoria, Australia.

Hybrid materials which consist of inorganic nanoparticles and organic matrices have been attracting much attention as novel refractive index engineering materials for a wide range of applications including filters, planar-gradient index lenses, reflectors, optical wave-guides, optical adhesives, anti-reflection films, holographic information storage devices, and optical coupling materials. Of particular importance for those applications is high optical transmittance at the wavelength of interest. Since nanoparticles have significantly low light scattering power, they are suitable for the preparation of composite films having high optical transmittance at the visible light range. In practice, there exist many obstacles to overcome to fabricate such nanocomposite films. The most serious problem lies in the trade-off between high transparency and high refractive index. In order to obtain a high refractive index of nanocomposites, it is necessary to use (i) nanoparticles having a high refractive index, and (ii) a high particle loading level, at the same time. However, Mie theory predicts that both of the two conditions can cause high light-scattering intensity, leading to low transparency. Although many experimental studies have been conducted on the refractive index engineering of nanocomposites, detailed investigation of the correlation between optical transmittance and refractive index at particle concentrations higher than 30 wt% has been scarcely reported for visibly transparent nanocomposite films, mainly due to the difficulty in achieving high particle concentration without particle agglomeration. In the present study, the correlation between refractive index and optical transmittance in the visible light region is investigated at particle concentration levels up to 60 wt%. As an inorganic - organic hybrid system, ZnO nanoparticles of ~ 30 nm dispersed in caprylic capric triglyceride were used. It was found that, while the refractive index of the nanocomposite was modified from 1.44 to 1.55 in a linear manner, the optical transmittance showed an abnormal behaviour as a function of particle volume fraction. The transmittance did not decrease according to the Beer-Lambert law but reached a near constant value above the particle loading level of 10 vol%. The results indicate the possibility of controlling refractive indices in nanocomposite films without altering their optical transmittance. * This research was conducted at Advanced Nanotechnology Ltd (108 Radium Street, Welshpool, Australia) under the Australian Federal Government Commercial Ready Grant Scheme (COM04097).

E1-S5.25
Conducting Microbeads-Insulating Matrix Composite Film. (#1070) Yojiro Yamamoto, Osaka Prefecture University, Sakai, Japan.

Soaring demand on miniaturization of consumer electronic products has been accelerating the development of high-density packaging and wiring technologies, in which electroconducting nano- and microsized particles plays an important role. For example, inkjet microprinting and anisotropic conductive paste/film technologies use such particles for their specific functions. Here, the anisotropic conductive film, standing for an adhesive insulator film dispersing a conducting particle, has been commercially available to make a huge number of local connections between input/output lines of a liquid crystal display (LCD) panel and external circuit in a single installation procedure since the 1980s. With this film/adhesive, conducting microbeads play a crucially important role in establishing reliable electrical connections. From this aspect, various types of metallic micropowders and electrolessly plated plastic beads have been utilized. In the latter case, the beads are elastic for making a reliable contact between a bump of an active component, such as LCD and large-scale integration (LSI), and an external bus line and can be metallized with either one or more different layers (for example, a nickel base layer with a gold layer on top). However, the conventional electroless plating technology to produce such metallized particles has been suffering from the low-cost efficiencies resulting from many environment-unfriendly processes and their inherent difficulties in controlling these multistep processes mutually as well as individually to achieve the best coating result.9 It is well known that the successful electroless plating on plastic materials requires precise control of the activation, catalyst formation, and subsequent nonfaradaic deposition processes. These processes should be designed rationally but are often managed by a number of empirically obtained know-hows. Furthermore, massive use of nongreen chemicals such as cyanide, chromic acid, and strong alkalis and acids is fundamentally incompatible to the demand for the low environmental release. Therefore, it is highly desired to design and implement an alternative pathway to replacing these procedures with a more straightforward and environment-friendly technique. Currently inorganic nanoparticles and their arrays are attracting keen interest as potential key materials for nanoelectronics due to their unique physical and chemical properties.13-16 Here, the selfassembly technology can be effectively used to assemble wellorganized 1D-3D structures, where interparticle connections can be made in a controllable single-particle level. Among these materials, metal nanoparticles are one of the most frequently studied materials for various types of nanotechnology-oriented devices, and their distinguishing shapes and combinations, such as nanobarcodes, nanorods, and nanowires, can add unique functions to their devices. Recently, we have reported on the electroconductivity of gold nanoparticle array films, which were composed of gold nanoparticles and thiol molecules as a binder. The films are prepared by a single-step procedure that uses the self-assembly technique for deposition of a nanoparticle on a plastic substrate, and it was indicated that this technique can dramatically reduce the environmental release of waste chemicals in comparison to the conventional electroless plating technique. Here, we present an approach to extending this technique for microsized plastic objects.

E1-S5.26
Sol-Gel Synthesis and Properties of TiO₂/SnO₂ Composite Nanopowders. (#585) Huaming Yang, Chengli Huo, Peiwei Wu; Central South University, Changsha, Hunan, China.

Uniform TiO2/SnO2 composite nanopowders with different Ti/Sn molar ratio have been successfully prepared via the sol-gel route. The samples were characterized using X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), transmission electron microscopy (TEM) and infrared spectrum (IR). The crystal size of the as-synthesized TiO2/SnO2 nanopowders is about 80 nm according to the XRD calculation. XRD analysis shows that the diffraction peaks associated with SnO2 were not found in XRD patterns when the molar ratio of TiO2/SnO2 is less than 10/1. The photocatalytic degradation of methyl orange (MeO) in TiO2/SnO2 suspension was investigated. The results indicate that the TiO2/SnO2 nanopowders show higher photocatalytic activity than pure TiO2 when the molar ratio of TiO2/SnO2 is 10/1, but it will remarkably decrease with TiO2/SnO2 molar ratio of 1/1. The photocatalytic mechanism of TiO2/SnO2 nanopowders was discussed. In addition, the electric property of TiO2/SnO2 nanopowders suggests an inhibition electric effect at higher TiO2 content. TiO2/SnO2 nanopowders with Ti/Sn molar ratio of 1/10 shows a resistivity of 1400 &Omega &bull cm. The TiO2/SnO2 nanopowders indicate a potential application in photocatalytic and electronic materials based on its bifunctional characteristics.

E1-S5.27
Study of Nano-Detectors Fabricated Using Silicon Nanowires. (#997) Changyi Yang, The University of Melbourne, Parkville, Victoria, Australia.

Silicon nano-wires have recently been used as novel platforms for the fabrication of many useful nano-electronic devices. Owing to their spatially confined one dimensional structure, nano-wires exhibit unique electronic properties which may provide advantages over conventional substrate geometries. For example, nano-wires can be packaged at high densities and therefore have the potential to realize position-sensitive detector (2D) arrays with nanometer resolution. In this work, we report on the fabrication and characterization of high quality silicon nano-wire detectors. We describe their electrical characteristics and report on charge carrier transportation and collection efficiencies measured with the ion beam induced charge (IBIC) imaging technique using MeV He+ single ions in a nuclear microprobe.

E1-S5.28
Tunable Morphology and Optical Properties of Poly(Styrene-block-4-Vinylpyridine)-CdS Nanocomposites. (#89) Dong Yanmao, Lu Jianmei; University of Science an Tenology of Suzhou, China.

The Poly(styrene-block-4-vinylpyridine)-Cd2+(PS4VP-Cd2+) have been synthesized by reversible addition-fragmentation transfer(RAFT) polymerization using styrene and 4-vinylpyridine-Cd2+ complex as monomer. The PS4VP-CdS were prepared by in situ method. The photoluminescence (PL) properties of the nanocomposites and the charge-transfer process between PS4VP and CdS were studied. Results show that the morphology of the nanocomposites are influenced by the evaporation rate of solvent and the CdS content in composites. The PL performance of the nanocomposites is enhanced by CdS nanoparticles and the emission of PS4VP-CdS can be changed quantitatively. The PS4VP-CdS nanocomposites have potential optical applications.

E1-S5.29
Preparation and Optical Properties of Anti-Glare/Anti-Static Hard Coating Films by UV Curing. (#523) Jung Whan Yoo, Dong Shin Yun, Hyung Mi Lim, Seung Ho Lee; Nanomaterials and Applications Division, Korea Institute of Ceramic Engineering and Technology, Republic of Korea.

Jung Whan Yoo1*, Dong Shin Yun1,2, Hyung Mi Lim1, Seung-Ho Lee1 1Composite Materials Team, Korea Institute of Ceramic Engineering and Technology, Seoul, Korea ; 2Department of Chemistry, Korea University, Korea *jwyoo@kicet.re.kr Anti-static/anti-glare(AS/AG) hard coating films have widely been used as outside protecting film in display panel such as LCD, PDP, and cellular phone. In this study, we used various fillers like silica sphere, hollow silica sphere, and polystyrene latex to control surface reflectivity for coating film and measured the film optical properties such as transmittance, haze, surface resistance, and gloss. The characterization of coated film by SEM gives different particle distribution on the film surface depending upon filler type. Low density polystyrene latex was well dispersed on the film surface, which can diffuse light so that we can see clear scene. Surface resistance was examined by adding conductive powder and polymer with different loading amounts to coating solution. Key-Word : Anti-Glare, Filler, Haze, Gloss, Polystyrene

E1-S5.30
Size and Thickness Control for TiO₂ Hollow Spheres According to Reaction Parameter. (#780) Jung Whan Yoo, Dong Shin Yun, Hyeung Seok Lee, Seung Ho Lee; Nanomaterials and Applications Division, Korea Institute of Ceramic Engineering and Technology, Republic of Korea.

Jung Whan Yoo*, Dong Shin Yun, Hyeung Seok Lee, Seung Ho Lee Composite Materials Team, Korea Institute of Ceramic Engineering and Technology, Seoul, Korea *jwyoo@kicet.re.kr Titanium dioxide(TiO2) has been studied extensively because of its unique properties such as photocatalytic reactions and high photovoltaic efficiencies. To improve these properties, the morphologies and macroscopic structures of TiO2 have been intensively studied. A three-dimensional porous structure of TiO2 with a large surface area is known to exhibit an enhanced photocatalytic performance. The nanosized hollow spheres of TiO2 are promising because of their potential to provide a large surface/volume ratio. In addition, since this size is comparable to the wavelengths of the visible and UV lights, the diffractions on the hollow spheres and the reflections due to the shell structure would improve the functional properties of TiO2. In this study, we synthesized TiO2 hollow spheres by using polystyrene as template and controlled the size, surface areas and wall thickness, which were done by SEM, TEM, BET.

E1-S5.31
Effect of Catalyst and Different Temperature of Substrates on Morphology of ZnO Nanowires. (#602) Ramin Yousefi, Burhanuddin Kamaluddin; Solid State Lab, Physics Department, University Malaya, Kuala Lumpur, Malaysia.

We have successfully synthesized high-quality ZnO nanowires on Si (100) n-type and Si (111) p-type substrates by a simple physical vapor deposition method in a convention tube furnace. Thin film gold layer has been used as the metal catalyst in some substrates. We have used different temperatures for each type of substrates and high purity nitrogen gas as a carrier gas. We choose a best place for substrates in downstream of furnace, so we could obtain a very big aspect ratio (L/D) for all nanowires. Different types of ZnO nanowires and nanostructures can be obtained at different substrate temperatures. We have also examined the effect of gold as a catalyst on growth of nanowires and compared them with those samples which have no catalyst, and we observed straight nanowires in samples without catalyst and curved nanowires in samples of with gold catalyst. A few samples with gold catalyst have also nanoleaves that grow on the nanowires. The nanowires on samples with gold catalyst have bigger aspect ratio than nanowires on substrates without gold thin film. The as-grown samples were characterized by filed emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD) spectroscopy. We observed a strong peak of (002) in ZnO nanowires growth on a substrate without gold thin film that were placed in high temperature zoon, indicating that ZnO sample were oriented and the growth direction was along (001) and this result is agreement with FESEM pictures of this sample. We also observed a strong peak of (101) in ZnO nanowires growth on the substrates with gold thin film that placed in different temperatures.

E1-S5.32
Fabrication and Optimization of Radar Absorbing Structures Composed of Glass/Carbon Fibers/Epoxy Laminate Composites Filled with Carbon Nanotubes. (#984) Zhengquan Zhang, Tiehu Li, Deqi Jing; Northwestern Polytechnical University, China.

The radar absorbing structures (RAS), which can not only load bearing but absorb electromagnetic wave energy by inducing dielectric loss and minimize reflected waves, is a multifunctional composite. Therefore, many researchers have paid attention on the development of RAS. The essence of the RAS was reducing RCS of the object. The composites possess excellent specific stiffness and strength. The electromagnetic wave properties of the RAS can be tailored by controlling the content of the lossy materials. Radar absorbing structures laminate composites, which were composed of glass fibers, carbon fibers and epoxy resin filled with carbon nanotubes, were fabricated in a press mould. In the paper, the complex permittivity of the RAS laminate composites was measured by free shape measurement system, and the absorbing properties were simulated based on electromagnetic theory. As a result, two optimal double-layer RAS was obtained. The reflection loss was less -10dB in entire X frequency, and the lowest was -26.6dB. Keywords: radar absorbing structures, carbon nanotubes, permittivity, reflection loss

E1-S5.33
AlGaN/AlN Resonant-Cavity-Enhanced p-i-n Ultraviolet Photodetector. (#387) Xie Zili, Rong Zhang, Han Ping, Zhou Ningshen; Physical Department, Nanjing University, China.

AlGaN/AlN resonant-cavity-enhanced p-i-n ultraviolet photodetector Z. L. Xie , R. Zhang, P. Han, R. L. Jiang, B. Liu, P. Chen, H. Lu, N.S.Zhou,Y. Shi, Y. D. Zheng Department of Physics, Nanjing University and Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Nanjing 210093, China 1. Introduction The resonant-cavity-enhanced (RCE) photodetectors (PDs) may achieve wavelength selectivity, narrow spectral operation, high quantum efficiency, high speed, and applicability to wavelength division multiplex system.[1,2] Recently, the AlGaN-based ultraviolet (UV) RCE PDs were studied.[3-8] In this letter, a front-incidence AlGaN/AlN RCE p-i-n PD with an operating wavelength ?o=320 nm was designed and fabricated. 2. Experiment and results The PD structure was grown on 2-inch (0001)-oriented sapphire substrate by metalorganic chemical vapor deposition. [9] The 40.5-pair Al0.3Ga0.7N/AlN (30.8 nm/36.9 nm) distributed Bragg reflector (DBR) and the air/GaN interface serve as the back and front mirrors. The p-GaN/ i-GaN/ n-Al0.38Ga0.62N structure is formed in the resonant cavity. The back and the front mirrors provide a center reflectivity of 93% with a stop-band width of 12 nm and a reflectivity of 20% at 320 nm. [9] The total thickness of GaN absorption layers was set to 60 nm. The n-Al0.38Ga0.62N layers also serve as a space layer, and they were set to 555 nm thick to form a 5?0 cavity. The absorption in the cavity, which means optical quantum efficiency, is as high as 97% at ?o=320 nm. The device was fabricated by three main device process procedures. The photosensitive area of the device is 0.54 mm2. The current-voltage (I-V) characteristic and the spectral photoresponse of the PD without illumination were measured. It shows a turn-on at ~3.0 V with a current of 1 mA. The dark current is 3.6 nA at 0 V. The responsivity at 313nm is 14 mA/W. 3. Conclusions AlGaN-based RCE p-i-n UV PD for operating at a wavelength of 320 nm was designed and fabricated. The measured reflectance spectrum implied an optical efficiency of at least 45%. A response peak of 14 mA/W at 313 nm was obtained under zero bias. Acknowledgments The work is supported by 973 Project 2006CB6049, Nature Science Foundation of China 60721063,60676057. References: 1K. Kishino, M. ?nl?, J. Chyi, et.al., IEEE J. Quantum Electron. 27, 2025 (1991). 2M. S. ?nl?, S. Strite, J. Appl. Phys. 78, 607 (1995). 3K. Kishino, M. Yonemaru, A. Kikuchi et.al., phys. stat. sol. (a) 188, 321 (2001). 4M. Yonemaru, A. Kikuchi, K. Kishino, phys. stat. sol. (a) 192, 292 (2002). 5N. Biyikli, T. Kartaloglu, O. Aytur, et.al., MRS Internet J. Nitride Semicond. Res. 8, 8 (2003). 6N. Biyikli, I. Kimukin, B. Butun, et.al., IEEE J. Quantum Electron. 10, 759 (2004). 7T. Li, J. C. Carrano, C. J. Eiting, et.al., Fiber and Integrated Optics, 20, 125 (2001). 8H. A. Macleod, Thin Film Optical Filters, (Macmillan, New York, ed. 2, 1986) 9Z.L. Xie, R. Zhang, B. Liu, et.al., Journal of Crystal Growth 298 (2007) 409-412

11:00 AM *E2-S2.1 (invited)
Resonant Raman Scattering from Graphene and Narrow Graphene Ribbons. (#1189) Peter C. Eklund, Awnish K. Gupta, Humberto R. Gutierrez, Timothy Russin; Department of Physics and Materials Science and Engineering, The Pennsylvania State University, USA.

We present new results on n-layer Graphene (nGL) systems and narrow graphene ribbons: polarized scattering from edges of graphene (n=1) and nGLs, variable dispersion of the phonon bands as a function on n (the number of layers), anharmonic effects, effects of incommensurate stacking of the layers (in bilayer systems) aqnd finally new modes in ribbons possibly activated by transverse quantum confinement in the width of the ribbon. The Raman backscattering from the graphene edge produces a band at ~ 1350 cm-1 which is strongly polarized as if the EM wave is polarized along the average direction of the edge. Our real edges are produced from micromechanical cleavage of graphite. High resolution TEM shows that typical edges produced in this way appear to have a few nanometers of ripple perpendicular to the average edge direction. Even though we think this ripple should produce a mixture of zigzag ande arnchair segments, the scattering is strongly polarized. We have also studied the effects of incommensurate (I) stacking on the Raman spectra of graphene bilayers. Here we show that the I-stacking activates a new Raman band (which we call the "I-band") with two components: one near ~1360 cm-1 that is dispersive (50 cm-1/eV) and the other at ~ 1385 cm-1 which is not dispersive. Interestingly, the linewidths of most of the Raman bands in I-stacked bilayer syatems are found significantly narrower than commensurately stacked graphene bilayers and even graphene itself. All of our results point to the fact that I-stacking almost completely decouples the two graphene layers, a point of possible importance to electronic devices. We have also mapped out the dispersion of seven Raman bands observed in nGLs and will comment on how the observed dispersion relates to double resonant Raman scattering in nGLs. Studies of Raman scattering from narrow graphene ribbons (2-5 nm wide) and tens of microns long will also be presented. These ribbons were made by the Dai group at Stanford University. Here we show that new modes are activated in the G-band by transverse confinement similar to those observed in small diameter SWNTs.

11:30 AM *E2-S2.2 (invited)
Optoelectronic Properties of Nanohybrid Systems. (#1473) George Thomas K, National Institute for Interdisciplinary Science and Technology, India.

We have recently initiated a detailed research program on the design of nanoparticle conjugates of organic/inorganic molecules which enable the coupling of the intrinsic functionalities of molecular systems (binding, self-assembly, switching etc.) with the size and shape dependent optoelectronic properties of nanomaterials.¹ The presentation will provide examples of modulating the optical properties of nanomaterials by integrating them into higher order assemblies using electrostatic/supramolecular/covalent approaches.^2-10 The presentation will also highlight our recent efforts to understand the interfacial properties of hybrid nanomaterials and their potential application in optoelectronic systems. 1. Thomas, K. G.; Kamat, P. V. Acc. Chem. Res. 2003, 36, 888. 2. Thomas, K. G., chapter entitled ″Surface plasmon resonances in nanostructured materials,″ in Nanomaterials chemistry: Novel aspects and new directions, Rao, C.N.R.; Mueller. A.; Cheetham A. K. (Eds.) Wiley-VCH (2007) pp 185-216. 3. Joseph, S. T. S.; Ipe, B. I.; Pramod P.; Thomas, K. G., J. Phys. Chem. B 2006, 110, 150. 4. Sudeep, P. K.; Joseph, S. T. S.; Thomas, K. G., J. Am. Chem. Soc. 2005, 127, 6517. 5. Pramod, P.; Joseph, S. T. S.; Thomas, K. G., J. Am. Chem. Soc. 2007, 129, 6712. 6. Vinayakan, R.; Shanmugapriya, T.; Nair, P. V.; Ramamurthy, P.; Thomas, K. G., J. Phys. Chem. C 2007, 111,10146. 7. Ipe, B. I.; Yoosaf, K.; Thomas, K. G., J. Am. Chem. Soc. 2006, 128, 1907. 8. Yoosaf, K.; Ipe, B. I.; Suresh, C. H.; Thomas, K. G., J. Phys. Chem. C 2007, 111, 12839.. 9. Pramod P.; Thomas, K. G., Adv. Mater. 2008 (in press). 10. Pramod P.; Soumya, C. C.; Thomas, K. G., ACSNano. 2008 (submitted).

12:00 PM E2-S2.3
Endotaxial Nanoclustering of Ferromagnetic MnAs in Lattice-Mismatched Semiconductor Layers during Metal-Organic Vapor Phase Epitaxy. (#552) Shinjiro Hara, Hiroko Iguchi, Takashi Fukui; Research Center for Integrated Quantum Electronics, Hokkaido University, Sapporo and JST-PRESTO, Japan.

Ferromagnetic MnAs thin films with the Curie temperature above room temperature have intensively been grown on semiconductor surfaces by low-temperature molecular beam epitaxy for the fabrication of magnetic tunnel junctions. We have investigated ferromagnetic MnAs nanoclusters (NCs) self-assembled on GaInAs {111} surfaces by metal-organic vapor phase epitaxy (MOVPE). [1] It has been found that 'endotaxy' of MnAs NCs, which is the phenomenon that the deposited materials grow into the substrate materials as single crystals, is occurred in GaInAs/InP (111) A layers. It is crucial for the formation of ferromagnetic/semiconductor hetero-structure layers to understand the mechanisms of the endotaxy during the MOVPE growth of MnAs. Therefore, in this paper, we report MOVPE growth experiments for MnAs on GaInAs and GaAs {111} layers and structural characterization results for MnAs NCs. This paper also discusses the possible formation models for endotaxial nanoclustering into the substrate materials. We have found that highly-uniform hexagonal MnAs NCs with well-defined crystal facets are self-assembled on GaInAs (111) B surfaces when the growth temperature and the V/Mn ratio are 650°C and 1125, respectively. Here, V/Mn ratio is defined as a partial pressure ratio between group V and manganese sources. Typical NCs measured 100nm wide and 47nm high. The cross-sectional transmission electron microscopy (TEM) shows that the NCs' surfaces are atomically flat, and that the interfaces between the NCs and the underlying GaInAs layers are atomically abrupt. We conclude from the electron diffraction patterns that the NCs have hexagonal NiAs-type MnAs crystal structures, and that their c-axes are parallel to the [11-1] directions of zinc-blende-type GaInAs layers. On the other hand, we find that single crystal NiAs-type MnAs NCs grow into the underlying GaInAs layers in the case of the (111) A surfaces because of the endotaxy. The observed c-axes of the NCs are tilted against the [111] direction of the GaInAs layers. It was confirmed that no endotaxy of the NCs into the GaInAs and GaAs (111) B layers after the MOVPE growth of MnAs was observed presumably because the (111) B surfaces consist of arsenic atoms. To clarify the formation mechanism of the NCs in the (111) A layers, thermal treatments of the samples were carried out under various atmospheric conditions. Even after the annealing at 600°C in the atmosphere of manganese source gas and hydrogen (that is, no arsenic gas supply) after the growth of GaInAs and GaAs (111) A layers, we confirmed from cross-sectional TEM observations that single crystal NiAs-type MnAs NCs were embedded in the (111) A layers. Therefore, we conclude that Mn ad-atoms on the surfaces diffuse into the underlying layers, and then, MnAs crystals are formed in the GaInAs and GaAs layers. High arsenic partial pressures are required for suppressing the endotaxy. [1] S. Hara and T. Fukui, APL, 89, 113111 (2006)

12:15 PM E2-S2.4
Crystalline-Amorphous Fe-Sm-Ta-N Magnetic Nano-Droplets Processed by Pulsed Laser Deposition at 157 nm. (#1114) Spomenka Kobe¹, Evangelia Sarantopoulou², Saso Sturm¹, Kristina Zuzek-Rozman¹, Zoe Kollia², Constantinos Alciviadis Cefalas²; ¹Department for Nanostructred Material, Jozef Stefan Institute, Ljubljana, Slovenia ; ²Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Greece.

The research effort on fabricating high energy magnetic films so far was mainly concentrated on intermetallic alloys, such as Sm-Co and Nd-Fe-B. In addition Sm-Fe intermetallic alloys with their high ability to absorb and bind nitrogen, which greatly enhances their intrinsic magnetic properties, seem to be the proper materials for growing thin magnetic films with enhanced magnetism, due to their high magnetic anisotropy, large saturation magnetization and high Curie temperature. As such they could be a candidate for MEMS and MAGMAS application.

Sm-Fe-Ta-N magnetic nanodroplets were fabricated by pulse laser deposition at 157 nm at low laser energy of 10 mJ per pulse in nitrogen background pressure. The target intermetallic alloy with the composition of Sm_13.8Fe_82,2Ta_4,0 was fabricated by arc-melting. The nanodroplets were deposited on a Si substrate coated with a ~ 100 nm thick layer of Ta to avoid chemical reaction between the highly reactive Sm and Si substrate.

The average composition of the deposited material reflected the stochiometry of the initial target. As prepared droplets were analyzed by the magnetic measurements using SQUID, nano-structures observation was performed by using field emission gun scanning electron microscope (FEG SEM) imaging equipped by electron dispersive X-ray spectroscopy (EDXS), which at the same time allows for the chemical analysis of the composition of the films. The surface morphology of the films was investigated also with AFM and MFM.

For more detailed analyses nano-spheres were examined by a field-emission electron-source high-resolution transmission electron microscope HR-TEM Jeol 2010F equipped with an energy dispersive x-ray spectroscopy (EDXS) (LINK ISIS EDS 300) and electron energy-loss spectroscopy (EELS) (Gatan PEELS 667).

Nanodroplets with the diameter between 5 nm up to 130 nm were observed with the HRTEM. Small spheres (<50 nm) were mainly amorphous, while larger spheres have a core-shell structure with a crystalline nucleus surrounded by an amorphous layer. The combined EDXS and EELS analysis confirmed that the composition of the inner crystalline part corresponded to the Sm₂(Fe,Ta)₁₇ phase (Sm_(at.%)/(Fe+Ta)_(at.%)=0.11) enriched with nitrogen. The outer amorphous layer was oxygen-rich with no detectable amounts of nitrogen and significantly different ratio of Sm_(at.%)/(Fe+Ta)_(at.%)=0.64.

These analytical results prove that nitriding of nanodroplets was taken place already in the plume and thus further post ablation annealing of the films was unnecessary for ferromagnetic response. The liquid nanodroplets solidify on the surface of a Si-Ta substrate in two phases. One is a crystalline nucleus, which is surrounded by an amorphous one. The bi-phase spherical nanostructure retains its ferromagnetic response of its crystal nucleus far more efficiently than the high porosity crystal structures grown at higher laser energies because of their accelerated oxidization. Besides the HRTEM analysis, also the magnetic measurements show that the soft magnetic alloy Sm_13.8Fe_82,2Ta_4,0 reacted with nitrogen and formed nitride already in the plum by obtaining the coercivity of 250 mT. With post ablation thermal treatment and further nitriding the coercivity was doubled, which show that in the plum it was achieved a partial nitriding and the conditions still have to be optimized, if we want to avoid completely further annealing and nitriding.

LUNCH 12:30 PM - 2:00 PM

2:00 PM E2-S3.1
Synthesis and Characterization of Copper-Based Nanoparticles Using Liquid discharge and Cu Electrode. (#1057) Neculai Apetroaei, Nagahiro Saito, Osamu Takai; EcoTopia Science Institute, Nagoya University, Aichi, Japan.

Copper-based nanoparticles have been attracting attention due to their applications in gas sensors, magnetic storage, solar energy transformation, semiconductors, catalysis, heating or cooling transfer fluid and antimicrobial functions. These properties are dependent on the size and shape of the particle and therefore it is very important to be able to control the morphology of these nanomaterials. Preparation of copper-based nanoparticles by copper electrodes thermal evaporation in liquid discharge is proposed. The discharge was produced between two pure copper cylindrically electrodes immersed in liquid, a high voltage power supply (0 - 4 kV) generates bipolar pulses from 1 to 10?s and frequency from 1 to 30 kHz. The copper aerosols from the electrodes can be condensed to form nanoparticles of Cu-based immediately by the cooling media. The used dielectric liquid was: distilled water and solutions (mixture of de-ionized water, ethanol and ethylene glycol). As protective agent to prevent the nascent Cu nanoparticles from oxidation in the liquid was used ascorbic acid and hydrazine. As capping agent, a surfactant with a critical influence on self-assembly of spherical Cu-based nanostructures was used CTAB (cetyltrimethylammonium bromide). Otherwise spindle-like nanostructures of CuO with an average width of 10 nm and length of 100 nm and CuO nanoparticles with average diameter of 10nm and clusters of 100-300nm diameter were formed in pure de-ionized water. Time evolution of the discharge voltage and discharge current, optical emission spectra of a discharge in de-ionized water and solutions are shown. The nanoparticles are characterized by transmission electron microscopy (TEM) X-ray energy dispersion spectroscopy (EDS) map and UV-vis absorption spectroscopy. Because Cu electrode was eroded and evaporated to form Cu and copper oxide nanoparticles and electrode surface changes can affect discharge efficiency, scanning electron microscope (SEM) images and EDS map of these electrodes of 1, 1.5, 2 and 3mm diameter are presented to a better understanding of the mechanism and the processes which appear near and on electrode in liquid discharge. Fabrication of copper-based nanoparticles by liquid discharge with copper electrodes is an alternative, cheap, effective and environmentally friendly method. Keywords: cooper-based nanoparticle, liquid discharge, water, ethylene glycol, ethanol. References: 1. Chih-Hung Lo, Tsing-Tshih Tsung, Liang-Chia Chen, J.Crystal Growth 277 (2005) 636. 2. Su-Yuan Xie, Zhi-Jie Ma, Chun-Fang Wang, Shui-Chao Lin, Zhi-Yuan Jiang, Rong-Bin Huang, Lan-Sun Zheng, J.Solid State Chemistry 177 (2004) 3743.

2:15 PM E2-S3.2
Investigation of 1D ZnS Nano and Heterostructures: Synthesis, Properties and Applications. (#50) Ujjal K. Gautam, Xiaosheng Fang, Yoshio Bando, Dmitri Golberg;

One dimensional structures, amongst all nanomaterials, hold the maximum promise for near future applications because of a number of reasons, e.g. the size confinement in two dimensions still leaves the other dimension practically macroscopic in order to be manipulated easily. ZnS is a direct and wide band-gap semiconductor with high refractive-index and transmittance in the visible range. Due to this, along with its intrinsic polarity due to the sequential stacking of the Zn and S layers, ZnS is one of the most useful semiconductors for a wide range of applications such as electroluminescence, nonlinear optical devices, flat panel displays, sensors, lasers, and a large number of other optical devices.1-4 Despite many advantages and possibilities, the properties of ZnS have hardly been explored when compared with ZnO, which has similar crystal-structure and chemical properties.5-6 This talk will discuss the growth and properties of ZnS based 1D nanostructures. The first phase of the talk will explain (i) the cathodoluminescence (CL) properties of individual and ensembles of 1D ZnS nanostructures probed by ultra-high spatially resolved cathodoluminescence microscopy. CL is the only contact-less method to investigate optical properties within a single-nanostructure. Our observations from the macroscopic-time resolved and nanometer-length resolved investigations show very intriguing luminescence behavior, such as accumulation of emission centers, radiation induced luminescence decay behavior and the first observation of room temperature band-gap emission from the individual ZnS nanostructures. CL properties of the pure and doped ZnS nanostructures will be compared. We will further discuss (ii) synthesis of specially designed hierarchical hetero-structure of ZnS and indium for field emission display devices. Indium is a type-1 superconductor. Magnetic measurements show unexpected retention of bulk behavior in these confined structures. REFERENCES 1. U. K. Gautam*, Y. Bando, J. Zhan, P. M. F. J. Costa, X. Fang, Dmitri Golberg (accepted in Adv. Mater.) 2. U. K. Gautam,* Y. Bando, X. Fang, J. Zhan, M. F. J. Costa, D. Golberg (submitted to ACS Nano.) 3. X. Fang, Y. Bando, G. Shen, C. Ye, U. K. Gautam, Pedro M. F. J. Costa, C. Zhi, C. Tang, D. Golberg Adv. Mater., 19 (2007) 2593. 4. X. Fang, U. K. Gautam,* Y. Bando, B. Dierre, T. Sekiguchi, and D. Golberg (Accepted in J. Phys. Chem. C) 5. X. Fang, Y. Bando, U. K Gautam, C. Ye, D. Golberg (accepted in J. Mater Chem.) 6. X. S. Fang, Ujjal K Gautam,* Y. Bando and D. Golberg, (Accepted in J. Mater. Sci. Technol)

2:30 PM E2-S3.3
Dye-Sensitized Solar Cells Based on Indium-Tin Oxide Nanowires Coated with Titania Layers. (#149) Hong-Wen Wang¹, Chi-Feng Ting¹, Miao-Ken Hung¹, Chwei-Huann Chiou²; ¹Department of Chemistry, Chung-Yuan Christian University, Chung-Li, Taoyuan, Taiwan ; ²Chemical Engineering Division, Institute of Nuclear Energy Research, Taiwan.

Uniformly-sized indium-tin-oxide (ITO) nanowires coated with titania layers have been synthesized and characterized. Nanostructured transparent conducting ITO nanowires protruding from the conducting substrate, covered with a separate active TiO2 oxide layer, were employed for the photoelectrode of dye-sensitized solar cells. This type of structure imparts a large surface area for efficient dye adsorption and, thus, efficient electron-hole formation and electron transport process. The concept was tested by growing ITO nanowires and ITO/TiO2 core-shell nanowires on F-doped ITO glass substrate by electrophoretic deposition (EPD) method, followed by a coating of titanium dioxide layer using doctor blade method to cover the ITO nanowires or ITO/TiO2 core-shell nanowires. The separation of charge generation and charge transport functions for optimization of this new designed dye-sensitized solar cell is investigated.

2:45 PM E2-S3.4
Preparation of W-doped Titanate Nanotubes for SCR Catalyst. (#785) Yeong-Ung Yun, Nam-Hee Lee, Yeong-Min Kim, Jong-Sun Hwang, Yong-Sung Choi, Kyeong-Soon Park, Sun-Jae Kim; Sejong University, Republic of Korea.

SCR (Selective Catalytic Reduction) support materials require high surface area, activity, tolerance to sulfur oxide poisoning, and so on. Especially, the high specific surface area is essential factor for dispersing active species like transition or noble metal elements. Among various support materials, for example, Al2O3, TiO2, zeolite, etc, TiO2-based titanate nanotube with layered structure has higher specific area compared with commercial TiO2 powders. To prepare TiO2 nanotube powders for an efficient SCR support, nanometer sized TiO2 powders as a starting material were hydrothermally treated in strong basic solution at 150 Celsius for 24 hours, with adding W ions of up to 30 wt% to increase active sites on support materials, and then calcined at temperatures in the ranges of 350 ~ 700 Celsius for 2 hours. Prepared powders were characterized using XRD, TEM, SEM, EDX, and a BET surface area analyzer. The results indicated that all as-prepared powders have layered structure and their TEM images show nanotube shape, showing BET value of ~ 300 m2/g. After calcination, W-doped titanates were maintained nanotube shape with anatase crystalline structure until 600 Celsius, whereas undoped titanates were easily changed short rod-like shape with lower BET values above 500 Celsius although they showed the same crystalline structure, compared with doped titanates, with the calcinations temperatures. Therefore, titanate nanotube, W-doped with an optimized content, has been usefully operated as a TiO2 support with high specific surface area for SCR catalyst.

3:00 PM E2-S3.5
Synthesis and Structural Analysis of Nanocrystalline Nd³⁺. (#1361) Pramod N Vasambekar, Department of Electronics, Shivaji University, Kolhapur, Sangali, Maharashtra, India.

Synthesis and structural analysis of nanocrystalline Nd3+ Substituted zinc ferrites T. J. Shindea, A. B. Gadkarib, P. N. Vasambekarc a - Department of physics, K.R.P. Kanya Mahavidyalaya, Islampur-415 409, India. b- Department of physics, G.K.G. College Kolhapur-416 012, India. c- Department of Electronics, Shivaji Uiniversity Kolhapur, India. Abstract Compositions having general formula ZnNdyFe2-yO4 (where y = 0, 0.01, 0.02 and 0.03) were synthesized by oxalate co-precipitation method. X-ray diffraction, Infrared absorption spectroscopy and Scanning electron microscopy were used to characterize the compositions. The single phase cubic spinel structure of the compositions was confirmed by XRD. Lattice constant was found to be decrease with increasing Nd3+ concentration. X-ray density increases with increasing Nd3+ content. The crystallite size of the samples lies in the range 29.74nm to 31.46nm. Infrared spectra show three absorption bands within the range of 400cm-1 to 700cm-1 and analysis shows that Nd3+ occupies B-site. SEM study shows that average grain size of the samples lies in the range 0.5826?m to 0.3823 ?m Keyword: Ferrites, Nanomaterials, XRD, IR, SEM. ______________________________________________ Corresponding author: T.J. Shinde E-mail - pshindetj@yahoo.co.in Telephone- +912346 228674 Mobile - 09860735543.

3:15 PM E2-S3.6
Surface Modification of TiO₂ Nanorods with Conducting Ligands and the Electrical Properties of Hybrid Conductive Polymer/As-Prepared TiO₂ Nanorods Photovoltaic Devices. (#459) Tsung Hung Chu, Yun Yue Lin, Shao Sian Li, Chi Hao Chang, Chiu Mao Li, Chun Wei Chen, Wei Fang Su; National Taiwan University, Taipei, Taiwan.

TiO2 nanorods have been synthesized by alkyl halide elimination by A. Paul Alivisatos, using oleic acid and TOPO as ligands. However, the application of these TiO2 nanorods to the hybrid solar cell is limited due to the insulating behavior of these surfactants. We are trying to introduce conducting ligands such as p-Terphenyl-4-carboxylic acid, Fluorene-9-carboxylic acid, and 9-Anthracenecarboxylic acid (ACA) to TiO2 nanorods to have improved charge transport properties. For the synthesis of OA and TOPO linked TiO2 nanorods, the procedure is that: 27g of octadecane, 26g of oleic acid, and 11g of TOPO were dried at 120 degree Celsius for 1 hour under argon flow to remove the water and oxygen molecules. Then, after it was cooled down to 90 degree Celsius, 3mL of TTIP and 1.7mL of TiCl4 was then injected to start the alkyl halide elimination reaction. The solution was maintained at 320 degree Celsius for about 60 minutes to complete the reaction. To modify the surface of the TiO2 nanorods, we mixed the acetone washed TiO2 nanorods in combination with the ligands at about 6:1 weight ratio, which were then dispersed in pyridine, and left under stirring at 75 degree Celsius until the solution turned into clear. The hybrid photovoltaic device of P3HT and surface-modified TiO2 are also prepared. In this way, we have found that the enhancement in the device performance can be achieved by replacing the insulating surfactant on the TiO2 nanorod surface with a more conductive ligand, which can play the role to assist charge separation efficiency or also to prevent from back recombination, giving a large improvement in the short circuit current and fill factor.

AFTERNOON BREAK 3:30 PM - 4:00 PM

4:00 PM E2-S4.1
Magnetic B-C-N Nanostructures from C Adatoms on BN Sheet and Nanotube. (#1333) Jia Li, Department of Physics, Tsinghua University, Beijing, China.

We study the adsorption, magnetic and diffusion properties of carbon atoms on zigzag single-walled boron nitride nanotubes (BNNTs), as well as the single-layer hexagonal BN sheet conventionally regarded as a BNNT with infinite radius, by spin-polarized density-functional calculations. It is found that the C adatom is energetically favorable to reside at the bridge site and correspondingly, the systems are spin-polarized with a local magnetic moment of 2.0 µB, The magnetic property of C adatoms on BNNTs is independent regardless of the tube diameter and the bonding between the C atom and BNNTs. The magnetization mechanism is discussed, and the dependency of magnetic moments induced on the distribution and content of C adatoms on the BNNT is also analyzed. It is shown that the C-adsorbed BNNT or BN sheet could be used as a building block of spintronic devices. On the other hand, the diffusion of C adatoms on BNNTs is anisotropic, predominately along the tube axis. A specific magnitude of the diffusion energy barrier with respect to the adsorption energy reveals that for different purposes, we could fabricate different functional devices on BNNTs or BN sheets by controlling the temperature. More precisely, at the low temperature a spintronic device (e.g., spin valve or spin polarization switch) could be formed by selective C adsorption, whereas the B-N-C superlattices or heterojunctions, maybe magnetic or not, could be grown by controllable C diffusion at the high or growth temperature.

4:15 PM E2-S4.2
Alignment Dependent Photoconductivity of Carbon Nanotubes Thin Films. (#691) Balaji Panchapakesan, Ye Liu, Shaoxin Lu; Electrical and Computer Engineering, University of Delaware, Newark, USA.

While there has been plenty of reports on the photoconductivity of single nanotubes and thin films of nanotubes, none of these studies have reported the effect of nanotube alignment on the photoconductivity in nanotube thin films.Nanotube thin films and bundles exhibit interesting behaviors including high bolometric and position dependent photoconductivity, optical transparency, fast charging and electro-mechanical actuation, and reversible expansion and contraction of nanotubes when exposed to light. Nanotube thin films could play an important role in a variety of micro-/nano-electro-(NEMS/MEMS), micro-/nano-opto-mechanical systems (MOMS/NOMS) and energy conversion. In this talk the alignment dependent photoconductivity of carbon nanotube thin films is reported. The photoconductivity exhibited an increase, decrease or even 'negative' values when the laser spot was on different positions between contact electrodes, showing a 'position' dependent effect of photoconductivity. Photon induced charge carrier generation in single wall carbon nanotubes and subsequent charge separation across the metal-carbon nanotube contacts is believed to cause the photoconductivity changes. While past studies on the photoconductivity of nanotube films have shown an internal quantum efficiency of 1.5% in vacuum, by partial alignment of nanotubes within the thin films produced an experimental internal quantum efficiency of 6.46% in air showing a dramatic increase in energy conversion efficiency. The alignment of the nanotubes within the films also showed a faster dynamic response than previously reported showing that the origin of photoconductivity is due to the existence of schottky barriers rather than molecular desorption. A net photocurrent of 6microamps and a photovoltage of 2mV was produced under laser intensity of 200 mW. We believe that charge carrier generation, and subsequent charge separation are all dependent on the alignment of nanotubes in thin films. Further recent studies on photomechanical actuation of nanotubes have shown that partial alignment of the nanotubes within the samples produced a faster kinetics of opto-mechanical actuation in nanotube thin films. It is expected that these effects are coupled there by leading to multiple physics at these low dimensions. Complete alignment of nanotubes within thin films can potentially produce a much higher internal quantum efficiency there by lending itself for energy conversion devices.

4:30 PM E2-S4.3
Electrical Characterization of Multi-Walled Carbon Nanotubes Using Test Structures Fabricated by Focused Ion Beam. (#545) Marcelo Macchi Silva, Alfredo Rodriges Vaz, Carla Verissimo, Jorge Leon, Stanislav Moshkalev, Jacobus Swart; Center for Semiconductors Components, University of Campinas, São Paulo, Brazil.

Integration of technologies for growth, characterization and selection of carbon nanotubes (CNTs) is extremely important for optimization of nanotubes synthesis and successful application of CNTs. This requires development of reliable technologies for successive growth, manipulation, contacting, processing, and measurements of electrical, optical and other properties of individual carbon nanotubes. One of promissing applications of multi-wall nanotubes in future microelectronics is their use for interconnections (wiring). For this application, detailed study and optimization of electrical properties of MWNT is required. In this work we investigate the electrical parameters of multi-walled nanotubes produced uisng chemical vapor deposition (CVD) method. For this study, micro- electrodes and pads of gold and palladium were pre-fabricated using photolithography and lift-off technique. Focused ion beam (FIB) was used to prepare test structures (nanocontacts) for nanotubes probing in a number of points between 2 main micro-electrodes, allowing multi-point electrical measurements. In particular, milling by FIB was used to make cuts between electrodes and to deposit Pt nanocontacts for multi-point measurements. These test structures were used for electrical characterization of supported or suspended (depending on the depth of cuts between electrodes) nanotubes deposited between main micro-electrodes using an ac (1-10MHz) dielectrophoresis method, followed (in some cases) by Ni or Pd electroless process for imrovement of contacts between the nanotube and metal electrode. The results were used to evaluate the intrinsic resistance and intershell conductance for multi-wall nanotubes obtained under different growth conditions. For analysis of data obtained with tubes of different lengths, the equivalent model of multi-walled nanotube as a resistive transmission line was utilized, and the parameters of the model (conductance of layers and intershell conductance) were obtained by fitting of experimental data.

4:45 PM E2-S4.4
p-Channel, n-Channel and Ambipolar Field-Effect Transistors Based on Functionalized Carbon Nanotube Networks. (#870) Eric Rolfe Waclawik¹, Roland G S Goh¹, John Marcus Bell¹, Nunzio Motta¹, Peter K-H Ho²; ¹School of Physical & Chemical Sciences, Queensland University of Technology, Australia ; ²National University of Singapore, Singapore.

The production of next-generation electronic devices based upon carbon nanotube platforms requires detailed knowledge of the physical basis of their operation. For one such device, carbon nanotube network field-effect transistors (CNNFETs), control over device polarity (p-type, n-type, ambipolar) is important for implementation in logic applications. CNNFET transport characteristics are influenced by charge trapping in the nanotube network and by substrate surface treatments. It is recognized that in contrast to individual-tube FETs, for CNNFETs, density of interface traps has a significant impact on these devices due to long channel lengths, multiple nanotube connections, nanotube types or states in the device (including the range of lengths, diameters, chiralities and bundle sizes) [1].The performance of CNNFETs made using solution-based techniques currently falls far below that of the CVD-grown CNNFETs and although high current carrying capacity CNNFETs have been demonstrated with solution cast SWNTs (e.g. Ko et al. [2]), they have very low on/off ratio (<3). The low on/off ratio is due to the presence of significant amounts of metallic tubes and to nanotube-bundling effects. In this paper we demonstrate that single-walled carbon nanotubes (SWNTs) functionalized by grafting octadecylamine chains to the tube-ends are effective to produce efficient CNNFETs with high on/off ratios. On/off ratio and field effect mobility are shown to be critically dependent on the mean bundle-size of the SWNT samples. Bundle-size is verified by XPS, AFM and solubility studies. AFM-analysis of mean bundle diameter and diameter distribution for samples spin coated onto plasma-treated SiO2 provided critical information used to analyse the electronic properties of the different carbon nanotube networks formed. By comparing CNNFETs possessing different degrees of bundling it is shown that thicker-bundle CNNFETs exhibit low on/off ratio but high field effect mobility whereas small-bundle samples yield devices of high on/off ratio but low field effect mobility. Also demonstrated is that removal of adsorbed oxygen by annealing and surface treatment of the CNNFET channel with a self-assembled monolayer of octadecyltrichlorosilane (OTS) can convert p- to n-type behaviour in the device through interaction of the network of nanotubes with the dielectric surface. Analysis of n-type CNNFET I-V curves predicts a carrier mobility of 6.0 cm2/Vs which is twice the mobility of the equivalent p-type CNNFETs. The electronic properties of CNNFETs are thus dominated by the channel rather than contact resistance, thus CNNFETs with high n-channel mobilities can be fabricated. These observations have significant implications for development of future CNNFETs technology and demonstrate a potential new route for the facile fabrication of p- and n-type devices. [1] S. Kumar, J. Y. Murthy, and M. A. Alam, Physical Review Letters, 95(6), 066802 (2005). S. Kumar, et al., Applied Physics Letters, 88(12), 13505 (2006). [2] H. Ko and V. V. Tsukruk, Nano Letters, 6(7), 1443-1448 (2006).

5:00 PM E2-S4.5
Synthesis and Characterization of Poly (sodium 4-styrenesulfonate) Coated Carbon Nanotubes / Poly (3, 4-ethylenedioxythiophene) Nanocomposites. (#67) Tran Thanh Tung, Korea University, Seoul, Republic of Korea.

In this study, Atom transfer radical polymerization (ATRP) initiators have been attached to MWNTs and poly (sodium 4-styrenesulfonate) (PSS) chains were grown from the surface. The well-dispersion of MWNT-PSS with the concentrations of 0.05 wt. % were present in the polymerization of EDOT monomers leads to improvement in the conductivity properties of polymer, especially steady in high temperature. The results show that sheet resistivities of PEDOT-PSS/MWCNT-PSS nanocomposite patterns as low as ~ 1k?/? could be achiveved. The stabilizing good conductivity properties of nanocomposite at 1500C for 72h aging in the oven have been compared to PEDOT-PSS/MWNT and PEDOT patterns. The bar coating method was used to make transparent conductive film on the polyethylene terephthalate (PET) film and properties of this film were investigated. Furthermore, different morphology and dispersion behavior of conductive filler were investigated by Fourier transform infrared (FTIR), high resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM) and optical microscope.

5:15 PM E2-S4.6
1-D "Crystalline-Amorphous" Carbon Nanoscale Heterojunction from Spark Plasma Sintering and its Rectification Behavior. (#136) Chunxu Pan, Xiang Qi; Department of Physics, Wuhan University, Hubei, China.

One-dimensional (1-D) heterojunction nanostructures have attracted tremendous interests because of their distinctive structures and properties, which are of importance for both scientific fundamentals in nanoscience and potential applications in nanotechnology. Generally, the heterojunction requires the fabrication with two steps at least for importing different chemical components or varying the growth conditions. Here, for the first time we report a high-throughput technique of fabricating novel 1-D "crystalline-amorphous" carbon nanoscale heterojunctions with the post-treatment of the amorphous carbon nanofibers (CNFs) in a spark plasma sintering (SPS) system. The as-grown amorphous CNFs were synthesized using ethanol flames on Fe-based substrates, and then treated in a SPS system with vacuum condition at temperature of 1500 ?C for 5 minutes without uniaxial pressure. The I-V curves of individual heterojunction and as-grown CNF were recorded on a Cascade Probe Station connected with a parameter semiconductor analyzer, according to the literature procedure. After SPS-treatment, the CNF has been partially reconstructed, i.e. a "crystalline-amorphous" junction successfully forms. HRTEM and EELS spectra clearly display two parts of the heterojunction: crystalline at the tip and amorphous in the rest. It was proposed that the formation of the 1-D nanoscale heterojunction is a result of the unique SPS. The typical I-V curve obtained by using the Au-heterojunction-Au configuration is highly nonlinear and asymmetric with a rectifying behavior. However, the observed phenomenon can be resulted from three contacts: (1) amorphous carbon segment - Au electrode; (2) crystalline - amorphous carbon junction; (3) crystalline carbon segment - Au electrode. Studies of the electrical transport property show that the as-grown amorphous CNF has semiconductor nature. Meantime, lots of literatures suggest that the crystalline carbon segment consisting of highly-crystalline graphite layers show metallic characteristic. Therefore, we conclude that the rectifying behavior is because of the intrinsic microstructure of the crystalline-amorphous carbon junction. The heterojunctions with rectifying behavior may have broad potential applications in nanoelectronics and optoelectronics, and the SPS technique could be a novel and distinctive approach to construct 1-D functional nanomaterials with high through-put.

E2-S5.1
Mechanical and Electrical Characterization of Nano-Ink Submitted to Different Curing Conditions. (#689) Renato Bonadiman, Ocileide Silva, Marco Elisio Marques, Germano Freitas, Tommi Reinikainen; Mechanical and Electronic Assemblies, Nokia Institute of Techonology, Manaus - AM, Brazil.

Direct printing of materials has gained significant interest as an alternative to conventional integrated circuit processing. In this sense, printed electronics provide a promising potential pathway towards the design of low cost products. Therefore, manufacturing electronic devices by printing techniques using nano-size material particles at low temperatures can revolutionize the electronics industry in coming years. Products based on printable electronics might include ultra cheap radio-frequency identification tags (RFID), inexpensive and disposable displays/electronic paper, parts of electronic assemblies (e.g. PWB and phone chassis), sensors, memories, and wearable user interfaces. PWBs could be replaced by an inkjetted printed substrate. Direct printing of nanoparticle inks could be used for the electrical interconnection of components (traces). Taking into account this scenario, the challenge is to provide sufficient quality of interconnecting traces considering the selection of appropriate material, more precise material deposition process and sintering. Moreover, the evaluation of the microstructure and its influence in the electrical and mechanical properties is necessary to understand and optimize the process. The mechanical behavior evaluated was the strain-life. It concerns low-cycle fatigue which involves large cycles with significant amounts of plastic deformation and relatively short life. The analytical procedure used to address strain-controlled fatigue is commonly referred to as the Strain-Life, Crack-Initiation, or Critical Location approach. In this work Ag-nano ink was printed over polyimide substrates and cured in different conditions of time and temperature. Polyimides are a class of high temperature polymers that are widely used in the fabrication of integrated circuits: as multilevel dielectrics, as die-attach adhesives, as passivants, as encapsulants and as a lithographic material. Nanomaterials exhibit remarkable specific properties due to their large surface to volume ratio, large surface energy, and spatial confinement that cannot be observed in bulk materials. Metal nanoparticles are known to exhibit large melting temperature depression due to the thermodynamic size effect. Due to its high conductivity and thermal stability, Ag nanoparticles suspensions have been widely used in the studies of conductive ink. In this work, design of experiments was the methodology applied to test the samples cured in different conditions of temperature and time. After that the samples were mechanically tested in order to determine their stress life. The data obtained were statistically treated. The obtained mathematical models were used to fit surface responses. The curves were applied to analyze the influence of cure conditions on the strain-life and resistivity. These responses were correlated to the traces microstructure previously analyzed by Scanning Electron Microscope (SEM).

E2-S5.2
Growth, Structures and Defect-related Optical Properties of ZnO Nanostructures by Laser Ablation in Liquid. (#722) Weiping Cai, Haibo Zeng; Institute of Solid State Physics, Chinese Academy of Science, China.

Pulsed laser ablation of metal targets in liquid media has attracted great interests, because such laser ablation in liquid (LAL) can produce the local extreme conditions. When a pulsed laser beam with enough energy irradiates on a metal target in a transparent liquid, a local plasma, with super-high temperature and high-pressure, will instantly be produced on the solid-liquid interface, and quench very quickly after one pulse due to subsequent adiabatic expansion of the plasma and its interaction with surrounding liquid media. Such extreme condition can lead to formation of some special nanostructures, and hence new properties and physical effects, which can not be obtained by the other conventional methods. LAL can also provide ideal model materials with special structures for the fundamental interest, such as, defect-related property study. Here we introduce our recent work about growth, structures and defect-related optical properties of ZnO nanostructures by 1064nm pulsed laser ablation of Zn target in liquid media, to demonstrate the advantages of LAL. The talk mainly includes: 1. Zn/ZnO core/shell nanoparticles and self-assembly; 2. ZnO and doped ZnO hollow nanospheres; 3. Defect-related optical properties of nanostructured ZnO.

E2-S5.4
Transport Properties of P3HT/surface Modified TiO₂ Nanorod Heterojunction System. (#486) Chia-Hao Chang, Yun-Yue Lin, Shao-Sian Li, Tsung-Hung Chu, Chun-Wei Chen, Wei-Fang Su; Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan.

Photovoltaic cells based on P3HT have found a promising future in recent years. In order to boost the device performance, we mix P3HT with surface modified TiO₂ nanorod and measure the transport properties by time-of-flight mobility measurement. In pristine P3HT, it is well-believed that mobility values are 3x10^-4 (cm² V^-1 s^-1) and 1.5x10^-4 (cm² V^-1 s^-1) for hole and electron respectively. With doping of surface modified TiO₂ nanorod, not only the transient curves become less dispersive but the mobility also show a great improvement. We further explore the transport properties with charge extraction linear increasing voltage (CELIV) mobility measurement and also find similar tendency. The increased carrier mobility coincides with the solar cell performance after the addition of TiO₂ nanorod.

E2-S5.5
Nanostructure Nb₂O₅-BaO-Na₂O-SiO₂ Glass-Ceramic and its Effect on Breakdown Strength. (#1219) Mao Changhui, Sun Xudong, Du Jun; North-east University, China.

Full density Nb2O5-BaO-Na2O-SiO2 glass-ceramics, which could be used as the dielectric energy-storage materials in fabricating high energy density devices, were prepared by means of rapid quenching and controlled crystallization under different temperature. DTA and XRD analysis show that NaNbO3 with perovskite structure and NaBa2Nb5O15 with tungsten bronze structure are formed as the dielectric phases from the glass at 680~720?C. XRD test and HRTEM observation show that the grain size of NaNbO3 and NaBa2Nb5O15 is around 20~50nm, which would slightly increase with controlled crystallization temperature. However, since the content of NaNbO3 and NaBa2Nb5O15 increase more quickly than the grow rate of grain size, nucleation is the dominate factor during controlled crystallization of Nb2O5-BaO-Na2O-SiO2 glass-ceramics. Further research indicates that breakdown strength of the glass-ceramics reduces with the increase of content and grain size of NaNbO3 and NaBa2Nb5O15 phases, which may due to the increase of structure defects between dielectric phases and glass phase.

E2-S5.6
Preparation of Nano-Al₂O₃/MgAl₂O₄ Composite Powder by Co-Precipitation. (#686) Wei Chen¹, Lan Zhou Yin¹, Xing Wang Li², Lan Zhou Yin¹; ¹School of Chemistry and Chemical Engineering, Central South University, Henan, China ; ²Zhengzhou Research Insitute of CHALCO, China.

Commericially available NH3H2O and Co(NH2)2 was used as precipitator, and AlCl3 and MgCl2 as the starting materials, Nano-Al2O3/MgAl2O4 composite powder were prepared by co-precipitation process. A suitable amount of NH3H2O, Co(NH2)2, AlCl3 and MgCl2 were dissolved in de-ionized water individually, AlCl3 and MgCl2 were mixed with each other, the mol ratio of Al3+ and Mg2+ was controlled between 4 and 5, the concentration of AlCl3 was controlled between 60 and 85g.l-1, NH3H2O solution was droped into the solution gradually, the solution was stired accompany. When the PH of the solution is greater than 6, A suitable amount Co(NH2)2 was added into the solution, the solution was heated to above 75? in a water bath, the Co(NH2)2 decomposed and NH3 was given off, the PH of the solution further heighten to 9~10, the Al3+ and Mg2+ will precipitated together in situ, they will changed into Al(OH)3 and Mg(OH)2 individually, the deposition was washed more than 5 times until the Cl-1 can't be check out using AgNO3 in the washing liquid. the free water in the deposition was deprivated in a freeze drier. After this process, the deposition was sintered more than 1300? for 60 minutes in a high temperature furnace, the The nano-Al2O3/MgAl2O4 composite powder will be made in this process. the mean diameter of the particle is less than 100nm. The grain size was analysised using scanning electronic microscope. Phase of alumina was measured using X-ray diffraction.

E2-S5.7
Sol-Gel Method for Ultrafine PT Ceramic Powder Processing. (#1091) Irinela C Chilibon¹, José—N Marat-Mendes², Rui Igreja², Paulo Inacio²; ¹Optoelectronics, INOE-2000, Bucharest-Magurele, Romania ; ²New University of Lisbon, Portugal.

PbTiO3, PT ceramics are prepared utilising as precursors Titanium (IV) isopropoxide Ti[OCH(CH3)2]4, 99.99% purity and Lead acetate trihydrate Pb(CH3COO)2?3H2O, 99% purity, and 2-methoxyethanol CH3OCH2CH2OH as solvent. Preparation of PbTiO3 gel was realized according to Schwartz studies [1], with some modifications, such as the reaction time, and hydrolyses conditions. Also, by utilizing nitrogen atmosphere flux the distillation process was faster [2]. The gel was prepared by addition of equal volumes of precursor solution (sol) and a solution, containing water (Rw = 2.5) and 2-methoxyethanol as solvent. So, the gelation of solutions was controlled through a hydrolytic polycondensation, by water adding. In the drying process, the densification and removal of volatile compounds induce some modifications into the gel structure, solvent removal leads to microporosity and therefore the area surface increases. During the gel conversion into amorphous powder through a thermal process, hydroxyl groups and some organic residuals are exothermic removed and induce appropriate mass decrease. Thereby, the water removal and burning of residual compounds, network collapses while the structure relaxes, and viscous sintering continues until the porous phase is eliminated. Densification of the amorphous gels by a thermal process implies structure relaxation, polymer condensation and viscous sintering. In the preliminary drying gel process, the gel is heated at 200 0C for 12 hours into a glass bottle, which is put into a silicon oil bath, and all this time it is rotated by a spinner. After that, the amorphous powder was heated into an oven at 300 0C for 24 hours. Secondarily, the drying process was made into an oven at 500 0C for 2 hours, and we obtained an amorphous powder. After that, the amorphous powder was crystallised into an oven at 800 0C for 2 hours, through out from oven and cooled in air. In the preliminary PT powder processing ultrasound gel revealed good influence in the ultrafine grains size [3]. REFERENCES: [1] R. W. Schwartz, J.A. Voigt, B.A. Tuttle, D.A. Payne, T.L. Reichert, R.S. DaSalla, Comments of the effects of solution precursor characteristics and thermal processing conditions on the crystallization behavior of sol-gel derived lead titanate thin films, J. Mater. Res., vol. 12, No. 2, p. 444-456, Feb. 1997 [2] J. Marat-Mendes, I. Chilibon, R. Igreja, M. do Carmo, C. Dias, P. In?cio, Influence of ultrasounds in the preparation and properties of PbTiO3 ceramics by sol-gel processing, European Micro and Nano Systems 2004, EMN04 Conference, Advances & Applications for Micro & Nano Systems, ESIEE, Noisy le Grand - Paris, France, Proc., p. 149-153, 20-21 October 2004 [3] J. Marat-Mendes, I. Chilibon, The ultrasound effects in the sol-gel processing of PbTiO3 powder ceramics, Twelfth International Congress on Sound and Vibration (ICSV12), July 11-14, 2005, Lisbon, Portugal (Proceedings on CD-ROM), Paper 988

E2-S5.8
Influence of Triethanolamine on Low-Temperature Hydrothermal Synthesis of Pure BiFeO₃ and their Applications as Visible-Light Photocatalysts. (#993) Chin Moo Cho, Jin Young Kim, Jun Hong Noh, Kug Sun Hong; Seoul National University, Republic of Korea.

Perovskite-type BiFeO3 (BFO) materials have attracted much interest due to their multiferroic properties at room temperature. Despite the fact that some work in this area has been undertaken, various research avenues such as synthesis, characterization, and the effects of magnetic fields remain to be explored. BFO powders have been prepared using a variety of synthetic methods, however, some secondary phases such as Bi2Fe4O9, Bi12(Bi0.5Fe0.5)O19.5, and Bi25Fe1O39 are usually formed during the synthesis. Various efforts have been made to prevent the formation of secondary phases and synthesize pure BFO at low temperatures. In this study, pure BFO nanopowders were synthesized at very low temperatures via a hydrothermal process in the presence of triethanolamine (TEA) and their structural, optical, photocatalytic and magnetic properties were investigated by X-ray diffraction, a field emission scanning electron microscope, a transmission electron microscope, and a superconducting quantum interference device magnetometer. BFO nanopowders are nearly spherical with an average size of approximately 100 ~ 150 nm. The UV-Vis absorption spectrum of BFO nanopowders was measured, and the calculated optical band gap value from the absorption spectrum is 2.12 eV. The photocatalytic activity of the BFO nanopowders was investigated in the decomposition of Rhodamine B (RhB). The concentration of RhB decreases with increasing reaction time and more than 30 % of RhB was decomposed after 3 h.

E2-S5.9
Thermal and Tribological Property Enhancement of Oil-Based Nanofluids. (#525) Cheol Choi, Mihee Jung, Kwangik Ahn, Jemyung Oh; Advanced Materials Research Group, Korea Electric Power Research Institute (KEPRI), Republic of Korea.

Nanofluids containing nano-scale solid particles show significantly increased thermal and tribological properties relative to those of conventional cooling and lubricating fluids. In this research, oil-based nanofluids were prepared by dispersing Al2O3, AlN and carbon nanoparticles with different particle size and shape into oil. Agglomerated nanoparticles were separated by bead-mill grinding or ultrasonication and surface modification was carried out simultaneously to improve the dispersion stability of the nanofluids. Effective thermal conductivity of nanofluids was measured by the transient hot-wire method, and the tribological behaviors of nanofluids were also investigated with a disk-on-disk tribo tester. The experimental results indicated that all prepared nanofluids had higher static/dynamic thermal properties than pure oil. It has also been observed that spherical nanoparticles have more effective dispersity and frictional properties in oil compared to fiber-shaped particles. On the other hand, fiber-shaped particles have superior effects on the convective heat transfer of nanofluids to spherical ones. For cooling application, using smaller nanoparticles was recommended, but an optimal particle size range was found for antifriction application, therefore either excessively fine or coarse particle would not be effective in increasing anti-wear ability.

E2-S5.10
Growth of Semiconductor Nanowires by Platinum and Their Properties. (#994) Hannah Jeong, Myoungha Kim, Tae-Eon Park, Ung-Kil Kim, Sojung Shim, Heon-Jin Choi; Department of Materials Science and Engineering, Yonsei Universitu, Republic of Korea.

Nanowires are one of the most promising nano building blocks for many applications in nano-electronics, nano-photonics and nano-bio informatics. To synthesize nanowires with high quality and single crystallinity, VLS mechanism with the aid of metal catalyst such as Au, Ni, and Fe has been widely used. However, these metal catalysts could form deep levels which provide trap centers in the band gap structure of nanowires. Deep level impurities have been known to be poison to the performance of nano-devices. To avoid such a problem, platinum (Pt) could be considered as an alternation since Pt has been reported to be free from deep levels. In this study, we explored growth of Si and GaN nanowires with the assist of Pt to figure out the feasibility of Pt as a catalyst for semiconductor nanowires. Pt successfully works as VLS catalyst for single crystal Si nanowires with diameter of 50 - 100 nm and length of several ?m in a SiCl4 based chemical vapour deposition process. The growth rates were higher with Pt than that of Au under all of processing conditions including SiCl4 concentration, growth time and temperature. The activation energy of nanowire growth through overall VLS reaction was measured as 80 kJ/mol and 130 kJ/mol with Pt and Au catalyst, respectively. The activation energy is comparable to that of decomposition of SiCl4 and, thus, this step is considered as the rate determining step in the growth of Si nanowires by VLS mechanism. The lower activation energy with Pt is believed to be associated with "chemical catalytic effect" of Pt for thermal decomposition of SiCl4 on the interface of vapour-catalyst droplet which is resulted in the faster growth of Si nanowires. We also successfully grew single crystal GaN nanowires with diameter of 100 nm and length of several ?m in a chemical vapour deposition process using Ga metal and NH3 as precursors. Ni has been widely used to grow GaN nanowires. Nevertheless, Ni is not only transition metal which provide trap center in the band gap structure but also ferromagnetic material which may perform the origin of ferromagnetism of compositional modulated GaN. These results suggest that Pt is a good candidate for the growth of semiconductor nanowires. In brief, we have successfully grown single crystal Si and GaN nanowires with the aid of Pt, which can exclude the drawbacks of existing catalyst. The electrical and optical properties of these Si and GaN nanowires will be discussed to emphasize on the effect of Pt on their properties.

E2-S5.12
Charge Separation in Titanate Nanostructures: Effect of Morphology Transformation. (#526) Oliver Diwald¹, Alexander Riss¹, Johannes Bernardi², Erich Knözinger¹; ¹Vienna University of Technology, Institute of Materials Chemistry, Austria ; ²Vienna University of Technology, USTEM, Austria.

Morphology changes induced by surface chemistry can provide important insights into photoexcitation processes on solids which are critical to photovoltaic and photocatalytic applications. At defined oxygen pressures we investigated charge separation on Na2Ti3O7 nanowires and scrolled up H2Ti3O7 nanotubes, two types of morphologies which by means of acid/base treatment can reversibly be transformed into each other. Some of the competitive processes photoexcited states undergo can be tracked by means of electron paramagnetic resonance and photoluminescence spectroscopy. A complementarity between efficient charge separation and radiative recombination of photoexcited states [1] was observed and clearly demonstrates the critical influence of morphology and interlayer composition on the photoelectronic properties of layered oxide nanostructures [2]. Furthermore, we investigated the thermal stability of these structures and carefully tracked the influence of annealing temperature on structure, spectroscopic properties and the efficiency of charge separation. [1] Riss et al. Nano Lett. 2007, 7, 433-438. [2] Riss et al. Angew. Chem. Int Ed. 2008, 47, 1496-1499.

E2-S5.13
X-Ray, SEM and Far IR Characterization of Y₂O₃ Added Mg-Cd ferrites prepared by Oxalate Co-Precipitation Method. (#1115) Ashok Bhairu Gadkari, Tukaram Jaysing Shinde, Pramod Nivrutti Vasambekar; Physics, SUK, Kolhapur, Maharashtra, India.

Polycrystalline CdxMg1-x Fe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) with addition of 5% of Y2O3, were synthesized by oxalate co-precipitation method and characterized by XRD, SEM and far IR techniques. The samples were sintered at 10500C for 5 hours. The X-ray diffraction measurements confirmed the formation of cubic spinel structure. Lattice constant (a), X-ray density, physical density, crystallite size, ionic radii on A- site and B-site (rA, rB), bond length on A-site and B-site, (A-O, B-O) and porosity were computed. The lattice constant is found to increase with increasing Cd2+ content and obeys Vegard's law. Crystallite size is calculated by Scherrer formula and found to lie in the range 28 to 33 nm. SEM micrographs show that the grain size increases with Cd2+ content. The addition of Y 3+ reduces the grain growth. . The IR spectra shows two strong absorption bands in the frequency range of 600 cm-1 and 400 cm-1 on the tetrahedral and octahedral sites respectively. Further it shows that Y 3+ occupies B-sites. Key words - Nanomaterials, Crystallite size, Ferrites, Lattice parameter, Porosity.

E2-S5.15
Precursor Cracking Evidence of Gold in Chemical Vapor Synthesis of Nanowires. (#322) Hsi-Lien Hsiao, Zhi-Yong Chen; Department of Physics, Tunghai University, Taichung, Taiwan.

Metal catalyzed vapor-phase synthesis has probably become the most extensively explored approach to prepare semiconductor nanowires. Gold has dominated as the catalyst metal of choice due to its chemical inertness and thermal stability. However, many aspects of metal catalyzing mechanisms during nanowires formation are not well understood. No comprehensive study on the influences of catalyst film thickness has been found in the literature. In this report, we present the first study on the correlation between thickness of gold thin film and morphology and composition of SiGe nanowires. Surprisingly, we found sputtered Au thin film is not only act as a eutectic catalyst on the vapor-liquid-solid nanowires formation, but also play an important role on the cracking of molecular precursors. SiGe nanowires are chosen as the example is due to its alloy composition nature and importance in silicon semiconductor industry. Here, we demonstrate that the SiGe nanowires can be synthesized on Au sputtered glass substrates at 400C by using hot-wall low-pressure chemical vapor deposition with silane, germane and hydrogen mixed gases. It is found that Au catalyst does not appear at the tip of SiGe nanowires until the thickness of sputtered Au thin film exceeds 2 nm. Further statistics estimation of the diameter and length of synthesized nanowires demonstrated exponential growth trend with respect to the thickness of Au catalyst. Moreover, Raman scattering characterization reveals the Ge contents of synthesized nanowires increase while increasing Au thickness. This observation was not reported previously and indicated the Au catalyst is not only act as the eutectic initiator during nanowires formation but also play important role on the cracking of molecular precursors during processing.

E2-S5.16
Production of Pores in Fluoropolymer Membranes by Ion Beam Bombardment. (#665) Robert Lee Zimmerman, Renato Minamisawa, Daryush Ila; Alabama A&M University, USA.

Producing structures in membranes at the nanometer scale can serve several applications such as to localize molecular electrical junctions and switches, and to function as masks. In previous work we demonstrated the fabrication of porous membranes in masked fluoropolymer films using scanned ion beam bombardment. The process dispenses the use of time consuming chemical and etching processes. Here we report on the creation mechanism of pores using ion bombardment. Aspects of the ion beam interaction with matter are explained as well as an analysis of the shape of the fabricated structures. The pores were produced using our feedback controlled ion beam apparatus and were analyzed using optical and atomic force microscopic (AFM) analyses. *Corresponding author: Daryush Ila, Center for Irradiation of Material, A&M University, 4900 Meridian Street, Normal, Alabama, USA 35762; Phone: 256- 372-5877, Fax: 256-372-8708; Email: ila@cim.aamu.edu

E2-S5.17
Characterization and Luminescence Properties Behavior of Li-Doped CaTiO3:Pr3+ Phosphors by Nanopowders and Bulk. (#247) Jong Won Chung, Byung Kee Moon, Jung Hyun Jeong, Jung Hwan Kim, Jong Seong Bae; Pukyong National University, Republic of Korea.

In conventional solid-state reaction, extensive ball milling is required; however, it may lead to possible contamination by unwanted impurities and degradation of the luminescent properties. To avoid such problems, various soft-chemical synthesis techniques have been extensively studied. So solvothermal reaction which offer molecular or nano-level mixing of constituents leading to chemical homogeneity are very useful to synthesize novel nano-size compounds with high crystalline. The aim of this study is to compare the luminescence characteristics of CaTiO3:Pr3+ phosphors which were synthesized by three different synthesis methods (solid-state reaction, and solvothermal reaction) and photoluminescence (PL) measurements. Pr3+ doped CaTiO3 phosphors were prepared by solid-state reaction and solvothermal reaction method, respectively. The doping various concentrations of Li were 0, 0.5, 1, and 5 w% of CaTiO3:Pr3+. The starting materials of solid-state reaction were Ca2O3, TiO3, PrF and LiF. The samples were after milling, sintered in air at 1200 oC for 2h. Ca(AcAc)3, Pr(AcAc)3, Titanium butoxide and Li(AcAc)3 were used as starting materials and they were dissolved in 2-Propanol. Stoichiometric amounts of above solutions were mixed and the composite was initially heated to 250 oC in air and continuously stirred in a mixture for 10h. The samples were dried at 50 oC in air for 5h, and the as-prepared samples were obtained. And the samples sintered in air at 900 oC for 4h. Their crystalline structures, surface morphologies and phase transitions were investigated according to annealing process by using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL). It was found that CaTiO3:Pr3+ phosphor synthesized by solvothermal reaction shows the nano-size, spherical shape but lower emission efficiency than that synthesized by solid-state reaction. It is also found that nano-size CaTiO3:Pr3+ phosphor synthesized by solvothermal reaction shows low quantum yield in comparison with that synthesized by solid-state reaction due to the presence of secondary phase.

E2-S5.18
Characterization and Luminescent Properties of Eu³⁺-doped Bulk and Nanocrystalline GdVO₄ Phosphors by Planetary Ball Milling. (#252) Hyun Kyoung Yang, Byung Kee Moon, Jung Hyun Jeong, Soung Soo Yi, Ki-Wan Jang, Ho Sueb Lee; Pukyong National University, Republic of Korea.

In this research, a facile synthetic route for the preparation of nanocrystalline GdVO4:Eu3+ by planetary ball milling method is reported, the as-grown powders were found to be amorphous, which crystallized to the tetragonal phase without GdVO4 by product after various temperature condition for 100 hours. The corresponding bulk GdVO4:Eu3+ were synthesized by high temperature solid-state reaction. All the products were systematically characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) and photoluminescent excitation spectra (PLE). The luminescence mechanism and the size dependence of their fluorescence properties are also discussed.

E2-S5.19
Synthesis and Photoluminescence of Eu³⁺-doped Y₂Sn₂O₇ Nanocrystals. (#713) Zuoling Fu, Byung Kee Moon, Hyun Kyoung Yang, Jung Hyun Jeong; Pukyong National University, Republic of Korea.

Pyrochlore oxides are of importance for their catalytic activities and high-temperature stabilities in various reaction processes [1]. The basic framework of the pyrochlore structures is a three-dimensional corner-sharing network of MO6 octahedra [2]. Recently, there has been a growing interest in strong luminescence of europium ions activated nanocrystals due to their promising applications in fluorescent lamps, field emission display and plasma display panels [3]. M2Sn2O7 stannates (M=rare earth) are conventionally prepared from solid state reactions at high temperatures (>=1400 oC). Besides their high energy consumption, these solid state reactions involve a series of laborious heating cycles at high temperatures and repeated grinding of starting oxide components. The resulting powders show extensive agglomeration and compositional inhomogeneity. Therefore, there is a real need to develop an alternative synthesis route for pyrochlore stannates. The hydrothermal synthesis technique has been shown to be promising in the preparation of complex oxides in terms of the relatively low reaction temperatures employed, high quality of the crystals obtained and, in some cases, reduction in sizes of the particles of the product solids. In this paper, Y2Sn2O7:Eu3+nanocrystals were prepared by hydrothermal synthesis method. Well-crystallized and phase-pure Y2Sn2O7:Eu3+ particles of ~20nm in size can be readily obtained at 900 oC, a temperature much lower than that of the conventional solid-state method. Furthermore, photoluminescence characterization of the Eu3+-doped Y2Sn2O7 nanocrystals was carried out and the results show that the material display intense and prevailing emission at 589nm belonging to the 5D0-7F1 magnetic dipole transition. Keywords: Hydrothermal Synthesis, Y2Sn2O7:Eu3+nanocrystals, Photoluminescence [1] J.N. Reimers, J.E. Greedan, J. Solid State Chem. 72 (1988) 390. [2] H. Mizoguchi, H.W. Eng, P.M. Woodward, Inorg. Chem. 43 (2004) 1667. [3] O.A. Serra, S.A. Cicillini, R.R. Jshiki, J. Alloys Compound 303-304 (2000) 316.

E2-S5.20
Preparation of SiC nano powder and its sintering behavior. (#1121) Soo-Ryong Kim, Woo-Teck Kwon, Seong Youl Bae, Younghee Kim; Korea Institute of Ceramic Engineering and Technology (KICET), Republic of Korea.

SiC powder can be produced generally through the Acheson process and it is required long carbothermic reaction time of SiO2 with carbon powder around 2200-2400?. Due to the high reaction temperature and long reaction times of the process, the powders produced have a large particle size and consist of mostly alpha phase SiC. Recently, various kinds of carbide and nitride ceramics have been prepared from organometallic polymeric precursors. The most important of advantage using polymeric precursor is the easiness of the preparation at low processing temperature. The derived microstructure and chemical composition is strongly dependent on the composition of the used polymer precursors. Polycarbosilane is the most typical polymeric precursor for SiC ceramic and has been widely used since the pioneering work done by Yajima et al. on SiC fiber. In this study, SiC nanoparticles have been grown in a flow reactor by thermal pyrolysis from a H2 and polycarbosilane oligomer mixture. The temperature was varied from 1200?C to 1400?C. In order to examine the pyrolysis residue after the reaction, the SiC powder was collected and analyzed with XRD. The X-ray diffraction result of the SiC powder shows the diffraction peaks around 35o, 60o, and 73o corresponded to the beta SiC phase. All the diffraction peaks were quite broad, which indicated that the SiC powder was in the early stage of crystallization at this heat treatment temperature. Sintering behaviors of SiC nano powder were examined at 1400? ~ 1600? under N2 atmosphere.

E2-S5.21
Preparation of Surge Resistant Nano-oxide/Polymer Composite for Enameled Wires. (#787) Hyo-Jin Oh, Yeong-Ung Yun, Sang-Chul Jung, Gyung-Soo Jeon, Kyeong-Soon Park, Sun-Jae Kim; Sejong University, Republic of Korea.

The lifetime of electronic motors and generators using enameled wires were usually determined by preventing the heat occurred from overlapping surge voltage. Conventional materials as H-type polysterimide, polyamideimide, and polyimide have application to lower temperature than 240 Celsius. Therefore, new surge resistance materials are necessary. In this study, nano-oxide dispersed polymer composite was prepared by dispersion-mixing process. Nanometer sized TiO2 and SiO2 powder as starting material were dispersed in organic solutions for example cyclohexane and conventional dilute agent as thinners. For steric stabilization, dispersion agent of polybutene-succinimide (PBS, OLOA1200) was added at 3 ~ 7 wt % to the nano-oxide mixed solvent. Zeta-potential of TiO2 and SiO2 was measured -40 mV and -50 mV after dispersing pure oxide particles in solvent. When added with dispersion agent in solvent, the zeta-potential was remarkably moved to -100 mV. Dispersed solution was mixed with polyimide then stirred for 5 hours. To compare the surge resistant, prepared nano-oxide dispersed polyimide and pure polyimide were repeatedly coated on copper wires, respectively. Dispersed nano-oxide particles were observed by scanning electron microscope. The nano-oxide powders were finely dispersed in the layer at nm orders. The surge resistant was conducted voltage endurance test. The life time of nano-oxide dispersed polyimide films were more than 100 times greater than that of conventional enamel wires.

E2-S5.22
Synthesis of Strain-Free ZnO Nanocrystallites Using Low-Temperature Oxidation Process and their Optical Properties. (#747) Tae-Won Kim, Jong-Woon Park, Bum-Ho Choi, Jong-Ho Lee; Korean Institute of Industrial Technology (KITECH), Republic of Korea.

We have successfully synthesized strain−free ZnO nanocrystallites emitting strong ultraviolet radiation at room temperature via the simple thermal oxidation of metallic Zn precursors at 380 °C. X−ray diffraction measurements showed only the diffraction peak from ZnO, revealing that metallic Zn precursors were successfully oxidized even at the low temperature of 380 °C. In addition, the peak position of (002) diffraction demonstrated that the lattice parameter of c-axis of the ZnO nanocrystallites was 5.208Å which was consistent with that of bulk ZnO. The mean size of the ZnO nanocrystallites determined using Scherrer's formula was ca. 30 nm. These results showed that the synthesized ZnO nanocryslallites were of strain−free. Room−temperature photoluminescence measurements using a cw He°Cd laser (λ=325 nm) showed a strong emission peak at 3.27 eV, which was ascribed to free excition recombination in strain−free ZnO nanocrystallites. In the case of epitaxial ZnO films grown on sapphire (0001) the room−temperature UV emission was observed at 3.292 eV, which was ascribed to the red−shift of free exciton recombination related strain effect. These results showed that the direct oxidation of metallic Zn to fabricate ZnO nanocrystallites may be feasible for realizing a nanophotonic device, since ZnO crystallites can be used as a nanometric light emitter in the device. In this study, we discuss synthesizing method of strain−free ZnO nanocrystallites using low−temperature oxidation process and their optical properties.

E2-S5.23
Structure and Nonlinear Optical Properties of CdS Nanocrystals-doped Zinc Borophosphate Glasses. (#964) Young-Seok Kim, Kyu Ho Lee, Tae-Ho Kim, Young-Joon Jung, Bong-Ki Ryu; Pusan National University, Republic of Korea.

The nonlinear optical properties of CdS-doped ZnO-B2O3-P2O5 glasses were measured by Z-scan technique using a nano-second pulsed laser. The non-linear refractive index (?z) estimated from Z-scan normalized transmittance was considered to include the optical Kerr effect (?K), the thermo-optic effect (?T) and the resonant non-linearity (?R) related to CdS content. The sign of ?z for glasses with CdS (1 ~ 7 wt%) was positive, whereas for glasses with 8 ~ 15 wt% CdS it was negative. The structure of the present glass system has been studied by Raman spectroscopy and FT-IR spectra, It was affected by the addition of CdS up to 5 wt%, when , it is believed, the Cd2+ ions occupied the interstitial positions in the glass network. The network structures of the ZnO-B2O3-P2O5 glasses have been confirmed to be basically similar to each other.

E2-S5.25
Preparation of SiC Nano Powder and its Sintering Behavior. (#1127) Soo-Ryong Kim, Woo-Teck Kwon, Seong Youl Bae, Younghee Kim; Korea Institute of Ceramic Engineering and Technology, Republic of Korea.

SiC powder can be produced generally through the Acheson process and it is required long carbothermic reaction time of SiO2 with carbon powder around 2200-2400?. Due to the high reaction temperature and long reaction times of the process, the powders produced have a large particle size and consist of mostly alpha phase SiC. Recently, various kinds of carbide and nitride ceramics have been prepared from organometallic polymeric precursors. The most important of advantage using polymeric precursor is the easiness of the preparation at low processing temperature. The derived microstructure and chemical composition is strongly dependent on the composition of the used polymer precursors. Polycarbosilane is the most typical polymeric precursor for SiC ceramic and has been widely used since the pioneering work done by Yajima et al. on SiC fiber. In this study, SiC nanoparticles have been grown in a flow reactor by thermal pyrolysis from a H2 and polycarbosilane oligomer mixture. The temperature was varied from 1200?C to 1400?C. In order to examine the pyrolysis residue after the reaction, the SiC powder was collected and analyzed with XRD. The X-ray diffraction result of the SiC powder shows the diffraction peaks around 35o, 60o, and 73o corrsponded to the beta SiC phase. All the diffraction peaks were quite broad, which indicated that the SiC powder was in the early stage of crystallization at this heat treatment temperature. Sintering behaviors of SiC nano powder were examined at 1400? ~ 1600? under N2 atmosphere.

E2-S5.26
Electrical and Mechanical Characteristics of TiO₂-C₆₀ Composite Films for Application of Electrodes in Electronic Devices. (#1141) Mi Chen, Horng Show Koo, Ghuan Jung Lin, You Wei Chang, Ming Wei Lee, Su Chen Lu; Department of Optoelectronic System Engineering, Minghsin University of Science and Technology, Hsinchu, Taiwan.

The physical characterization and analysis of TiO2 doped with fullerene in the dye-sensitized solar cells were presented. The nanostructured and porous TiO2 particles were synthesized by a chemical route and drying treatment. Besides, The self-synthesized fullerene have been purified by microwave digestion method. The purity of fullerene greatly affect the cell characteristics of the dye-sensitized solar cells. The paste of the micro-sized and nano-sized TiO2 particles doped with various weight ratio of fullerene were coated on the surface of ITO-coated glass substrate, which is the working electrode in the dye-sensitized solar cells. The various weight ratio of fullerene in porous TiO2 particles will lead to the variation of the cell characterization, energy conversion efficiency and Ish, of the dye-sensitized solar cells. These improvements maybe due to the enhanced adsorption of micro-sized and nano-sized TiO2 particles and fullerene for dye and electrolytic solution in the cells.

E2-S5.27
Electron-Phonon Interaction on the Nanocrystalline Semiconductors Probed by the Combination of the Surface Photovoltage and Photoacoustic Technologies. (#142) Kuiying Li, National Laboratory of Metastable Materials Manufacture Science & Technology, Yanshan University, Qinhuangdao, China.

The combination of the photoacoustic and the surface photovoltaic techniques was proved to be a promising experimental method to probe electron-phonon interaction (EPI) on the surfaces and sub-surfaces of the semiconductor photoelectronic materials, such as the crystalline CdTe, TiO2, and La0.8Sr0.2FeO3 nanoparticles, at room temperature upon illumination of UV - near IR light. The results show that the deexcitation process of photogenic free charge carriers may be treated in detail, and that the relationship between the surface electronic structures and the mechanisms of nonradiative transitions may be recognized by the combination in terms of these compounds. It is interesting that when the photon energy used was smaller than the photoelectric threshold of the nanoparticles, the deenergization processes of exciton pair, crystal field transitions, and the state-band transitions occurred mainly via the mutiphonon nonradiative deexcitation. But the charge transfer transitions between the main bandgap were hardly any dependent on the nonradiative transitions. In other words, the EPI of the materials mentioned above arise mainly from the interaction of photogenic free charge carriers, formed in the surface space charge region, and crystal lattice on nanoparticles, depends strongly on the sub-bandgap charge transfer transitions instead of the band-band transitions.

E2-S5.28
Electron-Phonon Interaction on the Nanocrystalline Semiconductors Probed by the Combination of the Surface Photovoltage and Photoacoustic Technologies. (#143) Kuiying Li, National Laboratory of Metastable Materials Manufacture Science & Technology, Yanshan University, Qinhuangdao, China.

The combination of the photoacoustic and the surface photovoltaic techniques was proved to be a promising experimental method to probe electron-phonon interaction (EPI) on the surfaces and sub-surfaces of the semiconductor photoelectronic materials, such as the crystalline CdTe, TiO2, and La0.8Sr0.2FeO3 nanoparticles, at room temperature upon illumination of UV - near IR light. The results show that the deexcitation process of photogenic free charge carriers may be treated in detail, and that the relationship between the surface electronic structures and the mechanisms of nonradiative transitions may be recognized by the combination in terms of these compounds. It is interesting that when the photon energy used was smaller than the photoelectric threshold of the nanoparticles, the deenergization processes of exciton pair, crystal field transitions, and the state-band transitions occurred mainly via the mutiphonon nonradiative deexcitation. But the charge transfer transitions between the main bandgap were hardly any dependent on the nonradiative transitions. In other words, the EPI of the materials mentioned above arise mainly from the interaction of photogenic free charge carriers, formed in the surface space charge region, and crystal lattice on nanoparticles, depends strongly on the sub-bandgap charge transfer transitions instead of the band-band transitions.

E2-S5.30
Development of Electrochemical Sensors for Calcium and Copper Ions by using Silicon Nanowires. (#1308) Kun-Lin Yang, Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore.

In this presentation, we will report the electrical detection of calcium and copper ions by using silicon nanowires (SiNWs) as channels in a chemically-gated field-effect-transistor (FET) configuration. The SiNWs were manufactured following a "top-down" approach which permits the production of 200 SiNWs in an array format simultaneously. To obtain a selective and sensitive layer for calcium sensing, the SiNWs were modified either with an amino acids or short oligopeptides, which are able to complex calcium ions or copper ions with high affinity. The FET device is very sensitive to calcium and copper ions in the nM to ?M range. It is also sensitive to other interference cations such as sodium, potassium and magnesium ions, but the response is much lower than the target ions at the same concentration. The study reported here may pave the way for designing an intracellular ion sensor (in combination with a patch clamp device) which permits the monitoring of ion concentration in real time.

E2-S5.31
Application of Silver and Gold Nanoparticles in Diazotization and Spectrophotometric Determination of Parathion Residues in Fruit and Soil. (#1424) Shilpa Sharma, Pandit Ravishankar Shukla University, Raipur (Chhattisgarh), India.

The catalytic activity of silver and gold nanoparticles in the spectrophotometric determination of parathion using 1-naphthol as a new coupling reagent to form an azo dye is described. The method is based on the reduction of nitro group present in parathion with zinc/HCl to form an amino derivative. The amino parathion thus formed is diazotized and subsequently coupled with 1-naphthol to form an orange colored azo dye in alkaline medium. The effect of size and shape of silver and gold nanoparticles in the time for diazotization is thus studied. The dye shows absorbance maxima at 500 nm and obeys Beer's Law in the range of 5-80 ug of parathion. The important analytical parameters and optimum reaction conditions have been evaluated. The method has been applied for the determination of parathion in soil and fruit sample.

11:00 AM E3-S2.1
Photoluminescence Property of Nitrogen-Terminated Nanocrystalline Silicon Particles in Pure Water. (#622) Yuichi Murata, Masaki Hiruoka, Keisuke Sato, Kenji Hirakuri;

Stability of photoluminescence (PL) properties from the semiconductor nanoparticles vary for the environment conditions such as air and/or solution since they depend almost entirely on the modification elements on the surface. Hydrogen-terminated nanocrystalline silicon (nc-Si) particles, which are one of the semiconductor nanoparticles, show stable visible luminescence in air. When the hydrogen-terminated nc-Si particles, however, were immersed in pure water, the visible luminescence was rapidly degraded by aging after a short period of time. This was closely related to the formation of the defects due to the hydrogen-desorption from the silicon-hydrogen bonds on the particle surface. Thus, the modification elements on the surfaces of nc-Si particles are very important to improve in the stability of luminescence in pure water. In this paper, the surfaces of nc-Si particles were modified with silicon-nitrogen (Si-N) bonds having the high chemical resistance in pure water. The nitrogen concentration dependence on the stability of luminescence from the nitrogen-terminated nc-Si particles will be discussed.The nitrogen-terminated nc-Si particles were prepared on the Si substrate by co-sputtering of Si3N4 chips/Si chips/silica mixture targets and post-annealing at 1100 ?C. The nitrogen concentration on the particle surface was controlled by changing the number of Si3N4 chips in the mixture targets. The samples after annealing were then treated in hydrofluoric (HF) acid steam to appear the nc-Si particles on the substrate. The HF treated samples were immersed in pure water for 400 hours. The surface composition and the luminescence property in pure water of the samples with the several kinds of the nitrogen concentration differ were estimated by using a fourier transform infrared (FT-IR) spectroscopy and PL measurements. The nitrogen-termination on the surfaces of nc-Si particles were confirmed by the FT-IR analysis, and the nitrogen concentration was increased from 0.7 to 5.7% with increasing the number of Si3N4 chips from 4 to 18 chips. The samples having various nitrogen concentrations emitted red light with the peak wavelength at 800 nm during the immersion in pure water, because the Si-N bonds were stably existed without the formation of the defects for the immersion time up to 400 hours. The stability of luminescence, however, was strongly depended on the nitrogen concentration. These results indicated that the nitrogen-termination to the nc-Si particles is one of the effective techniques on the realization in the stable PL property in pure water.

11:15 AM E3-S2.2
Magnetic Yard-Glass Shaped BN Nanotubes Filled Periodically with Fe Nanoparticles. (#442) Zhi Gang Chen¹, Jin Zou², Hui Ming Cheng¹, Max G. Q. Lu²; ¹Institute of Metal Research, China ; ²The University of Queensland, Brisbane, Australia.

Confinement of nanosized metals in nanotubes, through encapsulation of foreign materials inside nanotubes, often lead to unique physical properties that can be used to build nanoscaled hybrid systems. In particular, production of magnetic hybrid systems by filling magnetic particles inside nanotubes can be used for many magnetic applications, such as magnetic data storage, magnetic toners, ferrofluids, and contrast agents for magnetic resonance imaging. So far, various metals, carbides, nitrides, oxides, and fullerenes have been encapsulated in various nanotubes. However, it is a great challenge to periodically encapsulate magnetic nanoparticles into nanotubes and, in turn, to form one-dimensional magnetic nanostructures. In this study, we choose to encapsulate Fe nanoparticles in BN nanotubes (BNNTs). The reason for choosing BNNTs is that (1) the bandgap of BNNTs is independent of their chirality and lateral sizes; (2) BNNTs are chemically inert and thermally stable; and (3) BNNTs tend to form bamboo shape due to the stress inside the graphite sheets. These 3 intrinsic characteristics of BNNTs make it possible for BNNTs periodically encapsulated with magnetic nanoparticles to achieve novel physical phenomena in high temperature magnetism and nano-electromagnetism. In this presentation, we demonstrate a simple and novel method to synthesize yard-glass shaped BNNTs periodically filled with Fe nanoparticles using a floating catalyst method. In this extraordinary synthesis process, the yard-glass shaped BNNT units (each encapsulated one Fe nanoparticles) are formed first and subsequently connect into the one-dimensional BNNTs. The synthesized yard-glass shaped BNNTs have shown interesting magnetic properties [1]. [1] Z. G. Chen, J. Zou, F. Li, G. Liu, D.M. Tang, D. Li, C. Liu, X. L. Ma, H. M. Cheng, G. Q. Lu, Adv. Funct. Mater. (2007) 17, 3371.

11:30 AM E3-S2.3
Study on Electroless Plating Process for Iron-Cobalt Alloy Coating on MWCNTs. (#619) Yan Zhao, Yajuan Xue; School of Materials Science and Engineering, Beihang University, HaiDian District, BeiJing, China.

Zhao Yan, Xue Yajuan, Duan Yuexin School of Materials Science and Engineering, Beihang University Abstract To improve the magnetic property of MWCNTs, MWCNTs pretreated by washing, sensitizing and activating process were placed in an alkaline plating solution with supersonic and MWCNTs coated by fine and uniform iron-cobalt alloy were obtained in this research work. Keywords: MWCNTs, electroless plating process, iron-cobalt alloy coat 1. Introduction Recently, electroless plating process has been suggested to coat multi-wall nanotubes (MWCNTs) with metals. To improve the magnetic property of MWCNTs, the MWCNTs were pretreated by two kinds of activating processes and then placed in an alkaline plating solution with different temperature going with supersonic. 2. Experimental Materials The MWCNTs with the diameters mainly in the range of 10-30 nm and the length in the range of 5~15?m were produced by Shenzhen Nanotechnologies Co. and other chemicals were purchased from Beijing Chemicals Ltd. of China. Pretreatment of MWCNTs Two activating treatment methods which named as "one step" and "two steps" in water or ethanol were selected. "One step" is that the MWCNTs are put in the colloid-palladium solution produced by mixing SnCl2 and PdCl2 together. "Two steps" is sensitized in SnCl2 and then activated in PdCl2. Electroless iron-cobalt alloy coating on MWCNTs After pretreatment, Pd-modified MWCNTs were added into an ankaline electroless plating bath (PH=8.5) at 50?C or 60?C for a period, then iron-cobalt alloy coated MWCNTs were washed with distilled water and dried at 110?. Characterization The morphology and content of the coating on MWCNTs were characterized by FETEM and EDX by JEM2100F. 3. Results and discussion Comparison of activating treatment methods First water was selected as solvent to perform the activating treatment in two ways which are "one step" and "two steps". From table1 and table2, it can be found that the content of iron and cobalt increased when "two steps" method was selected. Furthermore from Fig.3 and Fig.4, it can be found that the iron-cobalt alloy coating on MWCNTs activated by "two steps" is more even and the area coated by iron-cobalt alloy is more extensive than those results by "one step". On the side, the shape of iron-cobalt alloy coating on MWCNTs activated by "two steps" is floccules and that activated by "one step" is dot. In another hand, ethanol was selected as solvent to perform the activating treatment in two ways which are "one step" and "two steps". From table3 and table4, it can be found that the content of iron and cobalt didn't change so much comparing with two activating methods. In addition, from Fig.5 and Fig.6, it can be found that the iron-cobalt alloy coating on MWCNTs activated by "one step" is more even and the area coated by iron-cobalt alloy is more extensive than those results by "two steps". Comparison of electroless plating processs The Pd-modified MWCNTs were added into an ankaline electroless plating bath (PH=8.5) at 50?C or 60?C for a period. From table5 and table6, it can be found that the content of iron increased when electroless plating process was performed at 60?C comparing with that at 50?C and the content of cobalt kept in the same value basically. Furthermore from Fig.7 and Fig.8, it can be found that the iron-cobalt alloy coating on MWCNTs is even and the area coated by iron-cobalt alloy is extensive coated at 50?C or 60?C. 4. Conclusion First the MWCNTs were activated by "one step" method in ethanol or "two steps" in water, then the Pd-modified MWCNTs were added into an ankaline electroless plating bath (pH=8.5) at 60?C for a period. As a result the MWCNTs coated by fine and uniform iron-cobalt alloy were obtained in this research work.

11:45 AM E3-S2.4
Narrow Size Distribution of Au Precipitates in SiO₂ at a Precise Depth. (#460) Supakit Charnvanichborikarn, Yin-Yin Jennifer Wong-Leung, Jim S Williams, Martin Conway; Electronic Materials Engineering Department, Research School of Physical Sciences and Engineering, The Australian National University, Australian Capital Territory, Australia.

Noble metal particles of nanometre size in silicon dioxide such as Au have been shown to exhibit interesting optical properties that open up potential device and sensor applications. The wavelength of the luminescence from such particles is strongly influenced by surface plasmon resonance (SRP) and is thus dependent on precipitate size. However, it is very difficult by conventional preparation processes of deposition and/or direct metal ion implantation to control the size and depth distribution of nanoparticles, thus limiting applications. In this study, using a combination method of ion implantation, high temperature annealing, and wet oxidation, we have successfully fabricated a novel silicon-based structure of Au nanoprecipitates at a precise depth in silicon dioxide. Nanocavities were initially formed in the top Si layer of a silicon-on-insulator (SOI) wafer by hydrogen implantation followed by an annealing at 850 °C for 1 hour. Au was then introduced into the near-surface region by implantation. Au precipitates of about 25 nm diameter were observed both at the cavity band and in the near-surface region after annealing at 900 °C for 30 minutes. A subsequent wet oxidation process segregated all such precipitates behind a growing surface oxide layer and ultimately trapped them in spherical shape at the interface between the two oxide layers. The structure was characterised by both Rutherford backscattering and channelling (RBS-C) and cross-sectional transmission electron microscopy (XTEM). The precipitate diameter was measured directly from TEM images and has an average value of around 50 nm. The width of the size distribution was found to be reduced compared to that formed by the method of direct implantation into SiO₂. This method, therefore, can provide Au precipitates with a tight size distribution at a precise depth (i.e., very narrow depth distribution) in SiO₂. Such a structure is amenable precipitate-induced luminescence at a narrow wavelength band and optical measurements are in progress to verify this expected feature.

12:00 PM E3-S2.5
Controlled Synthesis and Novel Optical Properties of Compound Nanocrystals. (#25) Shihe Yang, Hong Deng; The Hong Kong University of Science and Technology, Hong Kong.

Although impressive progress has been made in the research on lanthanide compound nanocrystals, it is still challenging to synthesize these nanocrystals with controllable size and shape. And new properties of the nanocrystals, both intrinsic and collective, are yet to be discovered. In the work reported here, we demonstrate our successful synthesis of uniform lanthanide compound nanocrystals with tunable shapes from square-plate to H-like via a simple and facile hydrothermal treatment strategy in a controlled fashion.1 The nanocrystal materials were thoroughly characterized by X-ray diffraction, transmission electron microcopy, fast Fourier transform (FFT), energy-dispersive X-ray spectroscopy (EDS), infrared absorption spectra, and photoluminescence spectra. Possible mechanisms of the lanthanide compound nanocrystal growth and size and shape evolution are proposed. We have uncovered and studied an unusual two-photon-exited avalanche photoluminescence property of the lanthanide compound nanocrystals. In fact, this, to the best our knowledge, represents the first systematic studies of two-photon-excited avalanche photoluminescence of any rare earth compound nanocrystals. Mechanistic aspects of the two-photon-excited avalanche photoluminescence will also be discussed. Our work combines synthetic and optical studies of the rare-earth compound nanocrystals and lays a foundation for reinventing their applications in optoelectronics among others, such as optical display, ceramic lasers, and biosensors.

12:15 PM E3-S2.6
Growth of Ge/GeO₂ Core-Shell Nanowires for Memory and Heterojunction Devices. (#467) Suvra Prakash Prakash Mondal, Vari Sivaji Reddy, Kaustuv Das, Achintya Dhar, Samit Kumar Ray; Microscience Laboratory, Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur, India.

Germanium nanowires are attractive due to their higher carrier mobilities and lower effective masses and compatibility with Si-based CMOS devices. Semiconductor nanostructures sandwiched/embedded in polymers are being investigated for applications in organic light emitting diodes, photovoltaic cells, flat panel displays and in organic field effect transistors. Memory devices using semiconductor/organic heterostructures make them useful for the realization of flexible and low cost polymeric electronic and optoelectronic devices. Nonvolatile flash memories with nanocrystal floating gates have been reported for low-power, fast access time and ultrahigh-density elements. Here we report the memory characteristics of Ge/GeO2 core-shell nanowires sandwiched between a tunnel silicon oxide and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) control gate in a MIS device configuration. The growth and optical characteristics of Ge/GeO2/CdS nanowire heterostructures useful for photovoltaic devices are also reported. The growth of core-shell nanowires was based on vapor-liquid-solid (VLS) mechanism using a Ge ingot, under controlled conditions with the assistance of a gold catalyst. Before deposition of Ge, a thin gold film was evaporated on oxidized p-type silicon substrates. The growth of nanowires was carried out at temperatures ranging from 750-950?C for different times in nitrogen ambient at a flow rate of 100 sccm. Transmission electron micrographs revealed the formation of Ge-GeO2 core-shell nanowires, having core diameter of 20-50 nm and shell diameter of 10-15 nm. The selected area electron diffraction pattern clearly indicated the formation of single crystalline Ge in the core region. The core-shell Ge/CdS nanowires heterojunction was fabricated using a simple chemical process and the hybrid heterostructure was prepared by spin coating of MEH-PPV solution on Ge/GeO2 core-shell nanowires. The capacitance-voltage characteristics (C-V) of core-shell nanowires/conducting polymer device exhibited excellent metal-insulator-semiconductor behaviour with hysteresis due to charge storage at 300 K. The C-V characteristics at different operating frequencies revealed that the hysteresis was mainly due to trapping of charge carriers in Ge nanowires rather than in the interfacial states. A simplified model based on tunneling of carries into the valence subbands of Ge was used to explain the charge storage behaviour. Room temperature and low temperature photoluminescence characteristics of the nanowires as well as core-shell Ge/CdS nanowire heterostructure showed dominant defect related emission from the GeO2 shell region whereas a strong band edge emission from CdS was recorded. A blue shift of the energy gap of CdS with decreasing temperature was observed from the PL spectra. The study indicates that the core-shell nanowire/conducting polymer heterostructure holds promise for potential applications in next generation nonvolatile memory for polymer electronic and optoelectronic devices.

LUNCH 12:30 PM - 2:00 PM

2:00 PM *E3-S3.1 (invited)
III-V Quantum Dot-based Optoelectronic Devices. (#1400) Lan Fu, G Jolley, S Mokkapati, Ian McKerracher, H. Hoe Tan, Chennupati Jagadish; Electronic Materials Engineering Department, Research School of Physical Sciences and Engineering, The Australian National University, Australian Capital Territory, Australia.

Quantum dots (QDs) grown by Stranski-Kranstanov method are of current interest for the application of high performance optoelectronic devices due to their unique three dimensional carrier confinement. Monolithic integration of QD based optoelectronic devices of various functionality is highly desirable for optical communication systems. In this talk, we will demonstrate the growth, fabrication and characterisation of two main III-V QD-based optoelectronic devices, namely QD lasers and QD infrared photodetectors (QDIPs), by metal-organic chemical vapour deposition (MOCVD). We will also present results on various QD structural design, growth and processing schemes to achieve spectral tenability of QD-based devices, including the approach of selective area epitaxy (SAE) [1], the use of dots-in-a-well (DWELL) structure [2] as well as the postgrowth technique of QD intermixing (QDI) [3]. These methods are essential for achieving high quality quantum dot-based devices and photonic integrated circuits.

[1] R. M. Lammert, T. M. Cockerill, D. V. Forbes and J. J. Coleman, IEEE Photon. Technol. Lett. , 6, 1167, (1994).
[2] S. Krishna, S. Raghavan, G. v. Winckel, P. Rotella, A. Stintz, C. P. Morath, D. Le and S. W. Kennerly, Appl. Phys. Lett., 82, 2574, (2003).
[3] L. Fu, P. Lever, H. H. Tan, C. Jagadish, P. Reece and M. Gal, IEE Proc.-Circuits Devices Syst., 152, 491, (2005).

2:30 PM E3-S3.2
Effects of Strain on the Distribution of Transition Metal Elements in GaN. (#777) Tae-Eun Kim, Seung-Cheol Lee, Jung-Hae Choi, Seung-Woo Han; Computational Science Center, Future Fusion Technology Laboratory, Korea Instititue of Science and Technology, Republic of Korea.

Diluted magnetic semiconductors (DMSs) that are made by doping of transition metal (TM) impurities into semiconductor hosts have been attracted many attentions for potential application of spin electronics. Among many DMS candidates, GaN based DMSs have been much interests due to the prediction of high Curie temperature. However, the onset of magnetism of GaN based DMSs has long been debated. On one hand, the observed magnetism was originated from the magnetic interaction between TM impurities and anions because any other phases except the matrix were not detected. On the other hand, another groups argued that the measured magnetism resulted from the clustering of TM impurities in the GaN hosts. Recent theoretical calculation supported the possibility of clustering of TM element in GaN. Recently, GaN nanowires doped with Mn showed different results. NEXAFS and anormalous scattering experiments on Mn doped GaN measured only Mn-N peaks not Mn-Mn peaks, which implies that Mn impurities are atomically distributed in GaN hosts while the system exhibited magnetic properties. The seemingly conflicting results motivate theoretical consideration. The high surface-to-volume ratio of nanowire deformed the crystal structure of wurtzite GaN. A compressive stress perpendicular to the growth direction reduces atom distances along the radial direction and a tensile stress along the growth direction increases atom distance in this direction. In the case of thin films, on the contrary, the extent of stress is not higher or practically stress-free than nanowires. In order to understand the effects of stress/strain on the distribution of TM impurities, we used first calculation approach. We calculated total energy of Mn doped GaN with/without stress. When additional Mn atom is introduced in one Mn impurity system, we calculated the changes of total energy with respect to the configuration. We found strong anisotropy of the total energy. When the second Mn is located at in-plane nearest-neighbor configuration, which corresponds to the atom is located on (0001) plane of wurtzite GaN, the total energy of the system is much lower than the out-of-plane configuration. Due to the large energy difference, the second atom favors to occupy in-plane position. The intrinsic stress of nanowires hindered the clustering of Mn impurities in GaN host. The stress favors to form linear chains of Mn impurities, which can explain the observed differences in experimental results. The more details will be presented.

2:45 PM E3-S3.3
New Solution for Nitrides Optoelectronics. Nanocrystalline GaN and GaN:Eu³⁺ Powder. Their Optical and Structural Properties. (#162) Artur Podhorodecki, Marcin Nyk, Robert Kudrawiec, Jan Misiewicz, Wiesław Stręk; Institute of Physics, Wroclaw University of Technology, Poland.

Gallium nitrides (GaN) based materials have been proven quite successful for fabrication of blue and green light emitting devices, however the realization of red light emitting devices has not been successful due to the difficulties associated with the synthesis processes. An attractive alternative may be the use of rare earth (RE) ion-doped GaN based materials. For this reason a great interest in RE-doped GaN, which combines the electronic properties of GaN with the unique optical properties of RE ions, is observed. It is mostly due to fact that RE ions, cover all visible emission range with very sharp lines and their optical characteristics are almost insensitive to the host material and temperature in contrast to their quantum well and quantum dot counterparts. However, the growth of very high quality GaN layers is still an expensive and difficult task for the researches since the GaN growth on foreign substrates leads to the high dislocations density, which ultimately affects the device performance and its lifetime. On the other hand, GaN with its emission at 3.4 eV, became a very interesting material from the point of view of UV emission-based optoelectronics. But similar like in the previous case, high quality GaN layer are difficult to obtain and the application area for all these devices is quite narrow. For all this reasons, GaN and GaN:Eu3+ nanocrystalline powder has been obtained by combustion method at different nitridation temperatures (850-1050oC) and different europium concentration (0.5-2%). By using X-ray diffraction and photoluminescence (PL), influence of the nitridation temperature as well europium concentration on the structural and optical properties have been investigated. Also by using PL and photoluminescence excitation spectroscopy the influence of grain sizes on the absorption and emission properties have been investigated.

3:00 PM E3-S3.4
Effect of N/Ga Flux Ratio on Morphological and Optical Properties of GaN Nanopillars Grown on (111) Si using Molecular Beam Epitaxy. (#1130) Agam Prakash Vajpeyi, Georgios Tsiakatouras, Adam Adikimenakis, Katerina Tsagaraki, Maria Androulidaki, Alexandros Georgakila; Microelectronics Research Group, Institute of Electronic Structure and Laser (IESL) and Department of Physics, University of Crete, Greece.

The catalyst-free growth of GaN nanopillars (NPs) were performed on (111) Si by plasma assisted molecular beam epitaxy. The GaN nanopillars grown on Si generate from the lattice mismatch strain and high surface energy of the nitrogen stabilized (0001) GaN surface. At constant substrate temperature of 750 oC, increase in N/Ga flux ratio results in lower diameter and lower density of NPs. The N/Ga flux ratio changed from five to twenty results in reduction of average diameter of NPs from 75nm to 55nm, respectively, and the density of the NPs decreased from 9x109cm-2 to 1x109cm-2. A higher growth rate of nanopillars compared to the compact film suggests the diffusion of Ga atoms from the uncovered substrate areas to the nucleated GaN pillars. Low temperature PL spectra at 20 K from GaN nanopillars show that free excitonic peak intensity decreased and the donor-acceptor pair emission intensity increased with increase in N/Ga flux ratio.

3:15 PM E3-S3.5
Intermixing of InAs/InP Quantum Dots Grown using Metal-Organic Chemical Vapour Deposition. (#959) Satyanarayan Barik¹, Lan Fu², H. Hoe Tan², Chennupati Jagadish²; ¹BluGlass Limited, Australia ; ²Electronic Materials Engineering Department, Research School of Physical Sciences and Engineering, The Australian National University, Australian Capital Territory, Australia.

Self-assembled InAs quantum dots (QDs) grown on InP substrates are very promising active materials for QD lasers and semiconductor amplifiers for optical fiber communications (1.3-1.55 micron) and devices for atmospheric pollution control systems. We report on the intermixing of the InAs/InP QDs grown using low-pressure horizontal flow metal-organic chemical vapour deposition (MOCVD). Intermixing is a simple post-growth process often involving rapid thermal annealing and can be used for bandgap tuning to monolithically integrate active-passive components of optoelectronic devices. However, the thermal stability of the QD structure needs to be high to achieve a large bandgap tuning range in the QD-based optoelectronic devices. We show that the insertion of a thin GaAs interlayer between the QD and buffer layers improves the thermal stability of the QDs. We also present the results of impurity free disordering (IFD) of the QDs containing a thin GaAs interlayer. We perform IFD by depositing a SiO2 or TiO2 layer on the QD sample followed by rapid thermal annealing. The process does not introduce any impurities and thereby, it retains high crystalline quality of the sample without significantly deteriorating the electrical properties or causing substantial optical losses. We show that both SiO2 and TiO2 layers promote IFD of the InAs/InP QDs indicating a dominant group V interstitial diffusion mechanism. We also discuss the effects of stress on the diffusion of vacancies and interstitials and estimate the stresses imposed by TiO2 and SiO2 on the QD structure.

AFTERNOON BREAK 3:30 PM - 4:00 PM

4:00 PM *E3-S4.1 (invited)
Current-carrying Capacity of Carbon Nanofiber Interconnects. (#1351) Hirohiko Kitsuki, Tsutomu Saito, Toshishige Yamada, Drazen Fabris, John R Jameson, Patrick Wilhite, Makoto Suzuki, Cary Y Yang; Center for Nanostructures, Santa Clara University, Santa Clara, California, USA.

Current-induced breakdown of carbon nanofibers (CNFs) is investigated for interconnect applications. Thermal and electrical resistances between CNF and metal electrodes are reduced using current annealing process, which also reveals that the maximum current density in the suspended CNFs is inversely proportional to nanofiber length and independent of diameter. This relationship can be described with a heat transport model that takes into account Joule heating and heat diffusion along the CNFs, suggesting that the breakdown depends on where the temperature reaches a threshold or critical value.

4:30 PM E3-S4.2
Electrical Conducting Behavior of Hybrid Nanocomposites Containing Carbon Nanotubes, Carbon Black and Graphite Nanoplates. (#579) Jang-Kyo Kim¹, Benzhong Tang²; ¹Department of Mechanical Engineering, Hong Kong University of Science & Technology, Hong Kong ; ²Hong Kong University of Science & Technology, Hong Kong.

Nanocomposites reinforced with hybrid fillers of carbon nanotube (CNT), carbon black (CB) and graphite nanoplates (GNP) were developed for electronic applications as the electric conducting adhesives and thermal interface materials. Special focus was placed on enhancing the electrical conductivity of the composites with balanced mechanical properties while lowering the cost of the final product. Epoxy-based nanocomposites were successfully prepared with varying combinations of CNT and CB, or CNT and GNP as conductive fillers and their electrical and mechanical properties were evaluated. It was shown that adding CB in CNT-epoxy composites can enhance the electrical conductivity: a low percolation threshold was achieved with 0.20 wt% CNT and 0.20 wt% of CB. CB enhanced the ductility of the nanocomposites, confirming the synergic effect of CB as effective multi-functional filler. Flexural modulus and strength remained more less the same as those with CNT alone. When the total reinforcement contents were fixed at 2wt%, the hybrid nanocomposite containing 1 wt% GNP and 1 wt% CNT achieved the highest electrical conductivity of 4.7x10-3 S/cm, which was more than two orders of magnitude higher than that of nanocomposite with 2wt% GNP alone. Although the flexural properties were only marginally changed by hybridization, the quasi-static fracture toughness could be enhanced significantly by increasing the CNT contents. Other synergic effects arising from the hybridization are discussed.

4:45 PM E3-S4.3
InN Nanostructure / Polymer Hybrid System for Photodetector Application. (#821) Wei-Jung Lai, Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan.

We have successfully grown various indium nitride (InN) one-dimensional nanostructures, including nanorods, nanotips and nanowires by using metalorganic chemical vapor deposition (MOCVD) method. Organic-inorganic hybrid phototdiodes were fabricated by incorporating conjugating polymer coated on InN nanostructures using solution process. Photoemission of InN nanostructures and surface states variation were investigated by IR PL measurement. Strongly reduced exciton lifetime measured by time-resolved PL technique indicated that charge separation efficiency increase between heterojunction interfaces. Also, the mechanism of charge transport was studied by using photoreponse spectrum. Experimental results showed that our devices have NIR photoresponse property and transient photocurrent results also show device possessed fast response speed. From these steady and dynamic photocurrent measurements, we can get the band diagram and density of states distribution of InN nanostructures.

5:00 PM E3-S4.4
Inkjet Printing: A Viable Tool for Processing Polymer Carbon Nanotube Composites. (#45) Marc in het Panhuis, The University of Wollongong, New South Wales, Australia.

Carbon nanotubes possess unique electrical and mechanical properties that make them desirable components in a range of potential applications.[1] However, their difficulty in processing represents one of the key challenges to researchers working in this area. Wet or solution based approaches for processing CNT involve two steps: dispersion of carbon nanotubes in common solvents using stabilizing agents, e.g. surfactants and polymers ]2-6] This is followed by techniques such as drop casting, filtration or spray painting allowing for the fabrication of nanotube containing materials with enhanced electrical, mechanical or optical properties.[1] A new and exciting processing method is based on inkjet deposition of water based CNT inks. Recent developments include the deposition of conducting films from single-wall carbon nanotubes (SWNT) and functionalized multi-wall carbon nanotubes (MWNT), as well as deposition of transparent water sensitive SWNT and MWNT films [6-9]. In particular I will demonstrate that the unique combination of (conducting electroactive or natural) polymers with conducting carbon nanotubes has been proven to be an ideal formulation with all of the demanding characteristics needed for inkjet printing. These materials could be readily deposited onto a wide variety of substrates such as photo paper, PET, Pt-ITO and Au-PVDF. Several important characteristics, such as optical, electrical, and electrochromic behaviour will discussed in detail. In conclusion, this presentation will discuss the development of inkjet printing as a viable tool for the fabrication of transparent conducting electroactive materials.[10] [1] M. in het Panhuis, J. Mater. Chem. 36, (2006) 3598. [2] K. Bradley, J.-P. C. Gabriel and G. Gr?ner, Nano Lett. 3, (2003) 1353. [3] R. Sainz, W. R. Small, N. A. Young, C. Valles, A. M. Benito, W. K. Maser, M. in het Panhuis, Macromolecules, 39, (2006) 7324. [4] W. R. Small, C. D. Walton, J. Loos, M. in het Panhuis, J. Phys. Chem. B 110, (2006) 13029. [5] M. in het Panhuis, S. Gowrisanker, D. J. Vanesko, C. A. Mire, H. Jia, H, Xie, R. H. Baughman, I. H. Musselman, B. E. Gnade, G. R. Dieckmann, R. K. Draper, Small 1, (2005) 820. [6] K. Kord?s, T. Mustonen, G. T?th, H. Jantunen, C. Soldano, S. Talapatra, S. Kar, R. Vajtai, P. M. Ajayan, Small 2, (2006) 1021. [7] J. Sumurel, J. Lewis, A. Doraiswamy, L. F. Deravi, S. L. Sewell, A. E. Gerdon, D. W. Wright, R. J. Narayan, Biotechnol. J. 1, (2006) 976. [8] M. in het Panhuis, A. Heurtematte, W.R. Small, V.N. Paunov, Soft Matter 3, (2007), 840. [9] W.R. Small, M. in het Panhuis, Small 3, (2007), 1500. [10] W.R. Small, F. Masdaloromoor, G.G. Wallace, M. in het Panhuis, J. Mater. Chem. 17 (2007), 4359..

5:15 PM E3-S4.5
Bio- and Nano-Materials Arrays Fabricated by Dip-Pen Nanolithography. (#379) Hua Zhang, School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore.

Bio- and nano-materials arrays have attracted significant attention due to their importance in a number of fields including biology, sensors, devices, etc. Many patterning methods, such as micro-contact printing and scanning probe microscopy (SPM)-based lithography, including dip-pen nanolithography (DPN) [1], have been developed in generating scale patterns from micro- to nano-meter scale. DPN is an atomic force microscopy (AFM)-based direct write method, which employs an inked AFM tip to deposit specific ink materials onto a solid substrate to form patterns [1]. Herein, by using DPN, the nanopatterns of amine-terminated polyamidoamine (PAMAM) dendrimers and metal nanoparticles were generated. The PAMAM dendrimer nanopatterns were used as the anchoring scaffolds to further in situ grow peptide arrays by the ring-opening polymerization (ROP) [2]. The metal nanoparticle nanopatterns were used as catalysts to grow carbon nanotubes (CNTs) arrays [3]. It provides a simple and highly effective method to generate bio- and nano-materials arrays. Reference: [1] (a) R. D. Piner, J. Zhu, F. Xu, S. Hong, C. A. Mirkin, Science 1999, 283, 661. (b) D. S. Ginger, H. Zhang, C. A. Mirkin, Angew. Chem. Int. Ed. 2004, 43, 30. [2] X. Z. Zhou, Y. H. Chen, B. Li, G. Lu, F. Y. C. Boey, J. Ma, H. Zhang, submitted. [3] H. Zhang, et al. unpublished results.

9:00 AM *E4-S1.1 (invited)
Mapping the Surface Plasmon Resonance Landscape of Gold Nanocrystals. (#404) Paul Mulvaney, School of Chemistry, The University of Melbourne, Parkville, Victoria, Australia.

This talk will provide an overview of our recent research into the spectroscopy and surface chemistry of single metal nanocrystals. In the first part of the talk, we focus on the possibility to study the optical properties of single metal particles using dark-field microscopy. It is now possible to routinely collect the scattered light from single metal nanocrystals and use this to study the effects of particle size and shape on the surface plasmon (SP) resonances. We show that the linewidth and energy of the SP resonance is acutely sensitive to the particle end cap geometry, to the aspect ratio and to atomic roughness on the particle surface. We look at the size and shape dependence of the SP resonance for over 200 different nanocrystals of various shapes and sizes. In the second part of the talk, we explore how SP resonance can be used to monitor chemical reactions and catalytic reactions on single nanocrystals. References: 1. "Gold Nanorods: Synthesis, Characterization and Applications", J.Perez-Juste, I. Pastoriza-Santos, L.M. Liz-Marzan, P. Mulvaney, Coord. Chem. Rev. 249, 1870-1901 (2005). 2. "On the temperature stability of gold nanorods: comparison between thermal and ultrafast laser-induced heating", Hristina Petrova, Jorge Perez Juste, Isabel Pastoriza-Santos, Gregory V. Hartland, Luis M. Liz-Marzan and Paul Mulvaney, PCCP, 8,814-821 (2006). 3. "Drastic Surface Plasmon Mode Shifts in Gold Nanorods due to Electron Charging", Paul Mulvaney,Jorge Perez-Juste, Michael Giersig, Luis M. Liz-Marzan, Carlos Pecharroman, Plasmonics, 1, 61-66 (2006). 4. "Gold nanorod extinction spectra",S.Prescott,P.Mulvaney,J. Appl. Phys. 99,123504 (2006). 5. "Routine Spectroscopy and High Resolution Microscopy of the Same Individual Nanocrystal using a Focussed Ion Beam Registration Method", Carolina Novo, Alison M. Funston, Isabel Pastoriza-Santos, Luis M. Liz-Marzan, and Paul Mulvaney, Angew. Chem. 46, 3517-21 (2007). 6. "Charge Induced Rayleigh Instabilities in Small Gold Rods" Carolina Novo & Paul Mulvaney, Nanoletters 7, 520-524 (2007).

9:30 AM E4-S1.2
Optical and Structural Characterisation of Vanadium Dioxide Thin Films and Nanoparticles for Novel Optical Applications. (#980) Annette Dowd, University of Technology Sydney, Sydney, New South Wales, Australia.

Vanadium dioxide undergoes a reversible rutile/monoclinic phase transition at 67°C, accompanied by large changes in optical and electronic properties, which could be exploited for solar switching applications and thermochromic pigments. The switching mechanisms of thin film and nanocrystalline VO₂ are poorly understood and the switch temperature and magnitude cannot be predicted. We expect that microstructure (especially size and strain) is important to the switching of the individual crystallites of various phases that comprise the film. A particular novel application of the switching capabilities of VO₂ is the 'regulatron', a hypothetical Au and VO₂ core-shell particle. The incorporation of the phase change material allows the plasmonic response of the Au to be switched externally as a result of the change in the dielectric function of the VO₂. We show the modelled response of this 'regulatron' and demonstrate how it is capable of maintaining a fixed temperature and a range of illumination intensities. We have prepared single crystal VO₂(M) nanoparticles and polycrystalline VO₂(M) thin films on fused silica. Visible and infrared spectroscopic studies of the nanoparticles at a range of temperatures show optical switching behaviour. Transmission electron microscopy results show that the particles are typically composed of 30-100 nm width single polygonal crystals with diffraction contrast and dislocations indicating a high degree of stress during synthesis. We discuss these results and their implication in wet chemical synthesis of VO₂. The switching mechanisms of thin film and nanocrystalline VO₂ are poorly understood and the switch temperature and magnitude cannot be predicted. We expect that microstructure (especially size and strain) is important to the switching of the individual crystallites of various phases that comprise the film. Optical characterisation of the films indicate a large reflectance switch and sharp spectral features that demonstrate films of very high quality. However analysis of the electronic energy structure of the VO₂ films shows that the high temperature metallic phase retains some semiconducting properties in its behaviour in the near-surface region. Scanning electron microscopy shows a highly structured film surface, with sub-100 nm features and also 200-300 nm platelet structures protruding from the surface. The platelets are probably another monoclinic polymorph VO₂(B), which is stable up to 500°C and could explain our observed continued presence of a semiconducting phase at high temperatures. Using grazing incidence X-ray diffraction, we confirm the presence of VO₂(B) which is often overlooked by other authors. The microstructural information concerning the crystallite size/shape and defect content will be analysed by a full study of diffraction peak broadening. The implication of these results in producing VO₂ thin films for optical switching applications will be discussed.

9:45 AM E4-S1.3
Formation of Ordered and Disordered Semiconductor/Metal Nanowire Arrays and their Plasmonic Behavior. (#705) S M Prokes, Dimitri Alexson, H D Park, O. J Glembocki, Ronald W Rendell; Electronic Science and Technology Division, Naval Research Laboratory, Washington, DC, USA.

Currently, there is significant interest in the growth of semiconductor nanowires. Since interesting and useful optical, electrical and mechanical properties have been reported in these systems, they may be attractive for a variety of applications, including optical sensors, FETs, and TFTs. However, many of the current applications are based on single nanowires, which have been carefully manipulated to form a device or structure. A better and more manufacturable option is the growth or formation of nanowires arrays, which can be easily integrated into a device configuration, with no complicated manipulation. As we will show, these random nanowire configurations can be extremely successful in plasmonics, where they serve as a very sensitive surface enhanced Raman spectroscopy (SERS) substrate, due to plasmon coupling of the randomly crossed nanowires. We will present results on the growth of several types of semiconductor nanowires, including, beta-Ga2O3, ZnO and InAs, and we will discuss several novel growth methods, structural and defect properties, as well as applications of these nanostructures to plasmonics. In the case of beta-Ga2O3, stoichiometric single crystal nanowires and nano-ribbons, as long as 100 microns, have been produced on a variety of substrates. The nanowire diameters can be controllably varied from 15nm to as large as 400nm, and they exhibit an intense, defect related photoluminescence, which is centered near 470nm. In the case of InAs, the growth of these nanowires is difficult, due to the very different vapor pressures of the constituents, and due to the rapid oxidation of In. However, we have developed a very simple and inexpensive growth process, which can grow high quality, single crystal InAs nanowire arrays. We will show results on the growth of InAs nanowire arrays, including random and ordered arrays, and random arrays on non-crystalline substrates, such as oxides and nitrides, and we will discuss a novel Si cluster-assisted growth of these nanowires. Finally, we will examine the plasmonic properties of these nanowires, and we will show that these semiconductor/metal composite nanowires can exhibit very strong surface enhanced Raman (SERS) signals, when arranged in a random 3D geometry. We will show that the intersections of nanowires are critical in generating the high electric fields necessary for this enhancement, and we will examine this effect under more controlled conditions. We will discuss the formation of nanowire arrays by in-situ growth, achieved by the control of nanowire material/substrate combination, as well as ex-situ nanowire arrangements, including combinations of e-beam lithographically produced array/nanowire combinations. The effects of the nanowire geometries and the resulting plasmon coupling will be discussed, showing the importance of the semiconductor/metal geometric configurations.

10:00 AM E4-S1.4
Fabrication of Double Nano-Cup Assemblies and their Enhanced Plasmon Absorption. (#462) Jingquan Liu¹, Burak Cankurtaran², Richard Wuhrer³, Michael Cortie³; ¹The University of New South Wales, Sydney, Australia ; ²Curtin University of Technology, Perth, Western Australia, Australia ; ³University of Technology Sydney, Sydney, New South Wales, Australia.

Double layered nano-cup assemblies of gold have been successfully synthesized using a combination of thermal evaporation and wet chemical etching. First a layer each of gold, aluminium and then gold again was sequentially thermally deposited at an angle of 50° onto a rotating substrate coated with a template of polymer microspheres. Next the polymer cores were removed by CH2Cl2 and the intermediate aluminium layer removed with dilute HCl. The resulting nanostructures were characterized using hi-resolution scanning electron microscopy, which confirmed that both the desired concentric structural arrangement and shell composition had been achieved. The double cup assemblies exhibited a red-shifted plasmon absorption at 735 nm when they were immobilized on the glass substrate pre-modified with aminopropyltrimethylsilane (APTMS). The optical properties of these complex core-shell structures were simulated using the discrete dipole approximation (DDA). There was good agreement between the calculated and simulated optical extinction spectra. Furthermore, it was found that the plasmon resonance and associated absorption of the inner cup was significantly enhanced when it was encased by a suitable outer structure. This provides an interesting new way to tune or enhance a plasmon resonance in a nanoscale structure.

10:15 AM E4-S1.5
Plasmon-Carrying Nanostructures for Photovoltaic Application. (#551) Nicholas Dmitruk, Alexander Korovin; Institute for Physics of Semiconductors, National Academy of Sciences of Ukraine (NASU), Kiev, Ukraine.

N.L. Dmitruk and A.V. Korovin Institute for Physics of Semiconductors NAS of Ukraine, Phone: +(38 044) 5256486; Fax: +(38 044) 5258342; E-mail: dmitruk@isp.kiev.ua Application of surface plasmons (SP) to increase photoconversion efficiency in solar cells (SCs) by using illumination with light beyond the photosensitivity spectral range has been advanced for the first time in [1]. Currently this problem is again generating interest in context of quantum dots and superlattices using. Recently a theoretical analysis of the effect of SPs excitation near a rough surface of a high-conductivity layer (say, a metal layer in Schottky contacts or a heavily doped emitter in a p-n heterojunction), as well as of excitation of surface plasmon polaritons (SPP) in 2D ordered system of quantum dots on a SC surface have been realized [2]. This work is devoted to use SPP excitation in the front microrelief emitter (metal, ITO etc) for enhancement of transmittance into SC. The theoretical calculation of light propagation through profiled metal film into semiconductor substrate was performed in the framework of new differential formalism [3]. Among two principal types of both interfaces interrelations of film there are: i) correlated (replicated profiles), and ii) anticorrelated (opposited profiles). It was shown that the thin anticorrelated absorptive films in surface barrier heterostructure give greater light transmittance in comparison with flat or correlated ones in wide spectral and angular range due to coupling between two SPP modes excited at both interfaces of thin film. Averaging of this transmittance spectrum over the whole AM0 energy solar spectrum with semiconductor energy gap limitation leads to increase of the short circuit current of SC up to twice in the optimal case of gold surface 1D grating (period, depth, average thickness). For example, the SC based on the anticorrelated 35 nm Au film (profiled by gratings with 30 nm depth and 600 nm period) depositing on GaAs substrate was considered and photocurrent values were obtained around 10 mA/cm2 contrary to flat one (5 mA/cm2). Besides, the anticorrelated films are intermediate type between films and nanowires (nanodots) ensembles and differential formalism allows us to determine of real nature of plasmonic modes working in the 1D periodic array of nanowires (for example, a periodic 1D array of conducting nanowires built into an air-semiconductor interface). Experimentally a quasiperiodic microrelief of quasigrating type on the InP or GaAs (100) substrates was formed by special chemical anisotropic etching. The following deposition of metal nanoparticles gives to a system of 1D array of nanowires. Their using in the SC will be useful for efficiency enhancement. 1. L.M. Anderson, Proc. SPIE 408, p.172 (1983). 2. N.L. Dmitruk, et al, Proc. 20th European Photovoltaic Solar Energy Conference and Exhibition, Barcelona, Spain, 2005, 6-10 June, p.553. 3. A.V. Korovin, JOSA A 25, p.394 (2008).

MORNING BREAK 10:30 AM - 11:00 AM

11:00 AM E4-S2.1
Vertically-Aligned ZnO Nanorod Growth on Various Substrates ZnO Homo-Buffer Layers. (#843) Sang-Wook Han, Chang-Ha Kwak, Soo-Young Seo, Seon Hyo Kim, Soo-Hong Park; Department of Physics Education, Chonbuk National University, Jeonju-City, Jeonbuk, Republic of Korea.

Vertically well-aligned ZnO nanorods were fabricated on Al2O3, metal/Al2O3 with ZnO homo-buffer layers by using a catalyst-free metal-organic chemical vapor deposition. X-ray diffraction (XRD) measurements demonstrated that the crystal quality of the ZnO nanorods grown on the ZnO homo-buffer layer was similar to that of the nanorods grown on the bare Al2O3 substrates and that the alignment of the nanorod orientations in the ab-plane as well as in the c-axis was much improved with the homo-buffer layer. Field-emission transmission electron microscope (FE-TEM) measurements from the interfaces of the nanorods and substrates exhibited the structural disorders existing in the bottom part of the ZnO nanorods grown on the sapphire and the ZnO homo-buffer layer, while no distinguishable disorder is observed at the ZnO/GaN interface. Extended X-ray absorption fine structure (EXAFS) measurements at Zn K edge revealed that a small but distinguishable amount of structural disorders existed in the Zn-O pairs in the beginning of the nanorod growth, suggesting that the structural strain due to the surface roughness of the ZnO homo-buffer layer and the lattice mismatch between the ZnO and GaN mainly contributed to an island growth in the beginning of the ZnO nanorod growth. We will also discuss the structural characteristics of the ZnO nanorods grown on the metal/Al2O3 substrtates.

11:15 AM E4-S2.2
The Growth of Surfactant Free of ZnO Nanoparticles by Liquid Phase Pulsed Laser Ablation. (#484) Madambi K Jayaraj, Reshmi Raman, Ajimsha Sreedharan, Aneesh P Madathil, Anoop Gopinadhan, Arun Aravind; Optoelectronice Device Labortory, Department of Physics, Cochin University of Science and Technology, India.

Liquid phase pulsed laser ablation has (LP-PLA) has proven to be an effective method for preparation of many nanostructured materials. In this paper we discuss the growth of surfactant free ZnO nanoparticles by LP-PLA technique without any by products. ZnO quantum dots were prepared in water, methanol, and ethanol medium. Transmission electron microscopy analysis confirmed the formation of good crystalline ZnO quantum dots with a uniform size distribution of 7 nm. Changing the laser fluence can vary the size of the particle. Particle sizes as observed from the size distribution are 7.1, 8, and 9.1 nm for ZnO QDs prepared at laser fluence of 25, 35, and45 mJ/pulse, respectively. From TEM analysis, the formation of other molecules like Zn(OH)2or ZnO/Zn core shell formation is not found. Because the ejected molten material from the target normally reacts with medium only at the outer surface, the ejected plasma readily cools, thereby reforming ZnO itself. These ZnO quantum dots colloidal solutions were stable and transparent highly luminescent and visible to naked eye under UV illumination. The maximum concentration of ZnO QDs that was achieved while maintaining transparency was 17.5 g/mL . The emission wavelength could be varied by varying the native defect chemistry of ZnO quantum dots and the laser fluence Clear, deep yellow, and bluish-violet emitting ZnO QDs fully dispersed in water, ethanol, and methanol were prepared directly from the ZnO targets by this technique without any byproduct. The Yellow emission has been attributed to the oxygen vacancy. This has been further supported by the experiments done with oxygen bubbling during the LP- PLA, which resulted in the suppression of yellow peak and the emergence of blue emission due to the zinc interstitials. The energy gap between the valance band and energy level of interstitial zinc is 2.9 eV. This is consistent with PL emission at 427 nm in the present study. The surface defects, mainly due to surface oxygen deficiency, these nanoparticles are charged. This surface charge provides a shield, preventing further agglomeration and thereby forming self-stabilized particles even in the absence of surfactant. The oxygen bubbling during the LP-PLA result in the reduction in surface defects and hence charge leads to the growth of nanoparticle size to micron size particles. Highly luminescent nontoxic ZnO quantum dots have exciting application potential as florescent probes in biomedical applications. Some of the trials on growth ZnO QDs in poly ethylene glycol for biological application will also presented.

11:30 AM E4-S2.3
Optical and Electrical Properties of SnO₂ Capped ZnO Nanowire Arrays. (#290) Quan Li, Liang Shi, Suikong Hark, Lian-mao Peng; The Chinese University of Hong Kong, Hong Kong.

Two-junction-nanowire arrays (SnO2 capped ZnO nanowire arrays on Zn substrate) have been synthesized using a two-step-solution-reaction. The single crystalline ZnO nanowires give reasonably intense band edge luminescence but also strong green emission likely due to surface defects. The SnO2 capping process on the ZnO nanowires also partially passivates the nanowire surfaces, leading to improved near band edge emission and the suppression of the defect luminescence. The nanowire array configuration allows a straightforward electrical measurement on the single nanowire junction (Zn-ZnO-SnO2). The I-V results indicate that little barrier exists in-between the Zn substrate and the nanowire. The observed linear I-V characteristic in some of the two-junction-nanowire suggests the possibility of using highly doped SnO2 as electrode grown on the ZnO nanowire, and thus constructing ideal electroluminescence device configuration--ZnO nanowire arrays naturally grown with two electrodes at both ends with little barrier at the junction interfaces. This work is supported by a grant from the research grant council of HKSAR (project No. 413706)

11:45 AM E4-S2.4
Abnormal Transmittance of Refractive-Index Modified ZnO - Organic Hybrid Films. (#64) Tak Tsuzuki, Centre for Material and Fibre Innovation, Deakin University, Victoria, Australia.

Hybrid materials which consist of inorganic nanoparticles and organic matrices have been attracting much attention as novel refractive index engineering materials for a wide range of applications including filters, planar-gradient index lenses, reflectors, optical wave-guides, optical adhesives, anti-reflection films, holographic information storage devices, and optical coupling materials. Of particular importance for those applications is high optical transmittance at the wavelength of interest. Since nanoparticles have significantly low light scattering power, they are suitable for the preparation of composite films having high optical transmittance at the visible light range. In practice, there exist many obstacles to overcome to fabricate such nanocomposite films. The most serious problem lies in the trade-off between high transparency and high refractive index. In order to obtain a high refractive index of nanocomposites, it is necessary to use (i) nanoparticles having a high refractive index, and (ii) a high particle loading level, at the same time. However, Mie theory predicts that both of the two conditions can cause high light-scattering intensity, leading to low transparency. Although many experimental studies have been conducted on the refractive index engineering of nanocomposites, detailed investigation of the correlation between optical transmittance and refractive index at particle concentrations higher than 30 wt% has been scarcely reported for visibly transparent nanocomposite films, mainly due to the difficulty in achieving high particle concentration without particle agglomeration. In the present study, the correlation between refractive index and optical transmittance in the visible light region is investigated at particle concentration levels up to 60 wt%. As an inorganic - organic hybrid system, ZnO nanoparticles of ~ 30 nm dispersed in caprylic capric triglyceride were used. It was found that, while the refractive index of the nanocomposite was modified from 1.44 to 1.55 in a linear manner, the optical transmittance showed an abnormal behaviour as a function of particle volume fraction. The transmittance did not decrease according to the Beer-Lambert law but reached a near constant value above the particle loading level of 10 vol%. The results indicate the possibility of controlling refractive indices in nanocomposite films without altering their optical transmittance. * This research was conducted at Advanced Nanotechnology Ltd (108 Radium Street, Welshpool, Australia) under the Australian Federal Government Commercial Ready Grant Scheme (COM04097).

12:00 PM E4-S2.5
Room Temperature Ferromagnetism in Cu-doped ZnO Nanowires. (#748) Tom Wu, Nanyang Technological University, Singapore.

The prospect of incorporating magnetic properties into semiconductor devices has provoked intensive research in developing diluted magnetic semiconductors (DMS). There have been many reports on DMS with magnetic ordering temperatures above 300 K, in particular, on transition-metal-doped ZnO. Even though that the dopants are dilute, there are still concerns that clustering of magnetic dopants can lead to ferromagnetic orders that are not intrinsic to the oxide host. In that sense, Cu as the dopant can eliminate the possibility of ferromagnetic clusters because that Cu and related oxides do not possess strong ferromagnetic properties. In this work, we carry out a comparative study of the room temperature ferromagnetism in Cu-doped ZnO nanowires (NWs) prepared by two distinct vapor-transport-based approaches. In the first method, we doped the ZnO powder first with Cu before the NW growth. In the second method, Cu is sputtered on aligned pure ZnO NWs first and then the doping was achieved by annealing. Both samples exhibit clear hysteresis loops, suggesting room temperature ferromagnetism. However, the magnetization of the 2nd method sample is much stronger than that of the 1st method. We attribute this contrast to the much higher density of defects in the NWs made with the 2nd approach. Therefore, our experiment strongly suggests that the defect-assisted formation of bound magnetic polarons induces the room-temperature ferromagnetism in Cu-doped ZnO NWs.

12:15 PM E4-S2.6
Photoluminescence Properties of SnO₂-core/ZnO-shell Nanobelt Structures. (#756) Chongmu Lee, Sunghoon Park, Hohyeong Kim, Chanseok Hong; Inha University, Incheon, Republic of Korea.

ZnO-coated SnO2 nanobelt structures were prepared by using thermal evaporation of Sn powders followed by atomic layer deposition (ALD) of ZnO. The growth mechanism of the SnO2 nanobelts was revealed to be vapor-liquid-solid(VLS) mechanism by scanning electron microscopic(SEM) observation. Dependence of the photoluminescence (PL) properties of the nanostructure on the ZnO-shell layer thickness was also investigated by using a room temperature PL spectroscopy analysis. Two distinct changes in the PL spectrum occur with an increase in the ZnO-shell layer thickness are as follows : 1) The intensity of the main PL peak centered around 595 nm characteristic of the SnO2 nanobelt decreases significantly, and a new peak tends to appear near 535 nm originating from O vacancies in the ZnO coatings as the ZnO layer thickness increases, resulting in a broad smooth emission peak forms from the yellow (535 nm) to the green (595 nm) region. 2) A new emission peak located at about 370 nm in the ultraviolet region characteristic of ZnO increases with an increase in the ZnO-shell layer thickness. The results suggest that the wavelength of the emitted light can be controlled to some extent by coating the SnO2 nanobelts with ZnO, yet the decrease in the PL intensity in the yellow region must be somehow overcome for this coating technique to be practically utilized for optical device applications. Besides the PL properties, the structural properties of the ZnO-coated SnO2 nanobelts structures were investigated by using SEM, transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX) analyses.

LUNCH 12:30 PM - 2:00 PM

2:00 PM E4-S3.1
Towards Industrial Scale Fabrication of Nanowire-Based Devices. (#426) Babak Nikoobakht, Surface and Microanalysis Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland, USA.

While optical lithography is suited for producing intricate architectures, its combination with "bottom-up" approaches becomes a very challenging issue. The challenge is to electrically address the coordinates of millions of nanoparticles (e.g., nanowires) on a given surface. Here, we describe a method that controls the registries of horizontally grown nanowires (NWs) and advances the current state-of-the-art NW device assembly technology. In this architecture, NWs are grown where the nanodevices will later be fabricated on. There is no need to transfer NWs to a different surface or perform NW alignment steps. Using only three photolithographic steps, this technique allows industrial scale production of nanodevices. First, zinc oxide NWs are grown selectively on a-plane sapphire at predefined gold sites. Growth direction of NW is controlled using the anisotropic crystal match between zinc oxide and the underlying substrate. Subsequently, metal electrodes are deposited on NWs at once and in a parallel fashion. To demonstrate the capabilities of this method, large numbers of top-gated zinc oxide NW field-effect transistors are prepared using optical lithography. This fabrication method is suited for fabricating a new generation of non-conventional nanodevices and nanosensors.

2:15 PM E4-S3.2
Effect of Sol-Molarity, Annealing Temperature and Nickel Concentration on the Optical Behaviour of Zn_1-xNi_xO_{(0 < x <0.3)} Thin Films. (#546) Amit Kumar Srivastava, Jitendra Kumar; Department of Material Science, Indian Institute of Technology Kanpur, India.

Bulk and thin films of ZnO have attracted attention in recent past because of their unique optical, semiconducting, piezoelectric, and mechanical properties. As a consequence, they have found numerous multifunctional applications, viz., solid state lighting, splitting of water, solar cells, sensors, actuators, transducers, high-frequency surface-acoustic wave (SAW) devices, displays thin-film transistors, spintronics, etc. Of particular interest is the transition metal (Mn, Co, Ni) containing ZnO system because of development in the area of dilute magnetic semiconductors. However, the investigations carried out so far are not quite consistent mainly due to resulting properties being very sensitive to the synthesis method and processing conditions. Hence, an attempt has been made to prepare thin films of Zn1-xNixO (0 < x < 0.3) by spin coating using acetate solutions derived from a cost effective sol-gel process (which allows homogenous dispersion of species at low temperature with accurate control of composition) and study the effect of sol-molarity, annealing temperature and nickel concentration on their phase (s), microstructure and optical absorption behavior. For this, thin polycrystalline films of ZnO have been first deposited on glass substrates by spin coating of a zinc acetate dihydrate solution in 2−methoxyethanol and mono-ethanolamine and subsequent annealing at 400-500 °C for 2h in oxygen ambient. They possess wurtzite - type h.c.p. structure but the lattice parameters depend on both the solution molarity (M) and the annealing temperature (T); typical values being a ∼ 3.248 Å, c ∼ 5.216 Å, and a ∼ 3.282 Å, c ∼5.148 Å for T ∼500 °C and molarity 0.8 M and 1 M, respectively. The atomic force microscopic observations reveal the presence of nanoscale spherical particles of average diameter ∼25 nm. The films exhibit (i) surface roughness ∼6 nm (ii) high optical transmittance (∼98−100%) in the wavelength range of 400−800 nm, (iii) sharp optical absorption in the interval 300 − 400 nm like that of a semiconductor, (iv) slight shift in transmittance plot towards higher wavelength with increase of both annealing temperature and the sol molarity and (v) energy band gap (Eg) in the range ∼3.33−3.31eV −attributed to quantum size effect (crystallite size being in the range ∼11−14nm). Thin films of Zn1−xNixO (0.1 ≤ x ≤3), prepared similarly using appropriate amount of nickel acetate tetrahydrate solution as well, continue to have a wurtzite-type h.c.p. structure, but, with somewhat lower lattice parameters and display reduced optical transmittance. It is shown that Ni2+ ions occupy normal Zn2+ sites and increase of nickel content (x) from 0.1 to 0.3 causes (i) decrease of lattice parameters from a ∼ 3.231 Å, c ∼5.184 Å to a∼ 3.226 Å, c ∼ 5.161 Å and (ii) decrease of average crystallite size from 29 to 20 nm, (iii) increase of the energy band gap Eg from 3.28 to 3.30 eV, and (iv) substantial decrease of optical transmittance from 90 to 50% at 400 nm.

2:30 PM E4-S3.3
1D ZnS Nanostructures: Controlled Growth and Field-emission Applications. (#49) Xiaosheng Fang, Yoshio Bando, Ujjal K Gautam, Dmitri Golberg; Nanoscale Materials Center, National Institute for Materials Science, Namiki, Tsukuba, Ibaraki, Japan.

One-dimensional (1D) nanostructures have recently stimulated great interest due to their potential value for understanding fundamental physical concepts and for applications in constructing nanoscale electric and optoelectronic devices since the discovery of carbon nanotubes.[1] ZnS is one of the first semiconductors discovered and probably one of the most important materials in the electronics industry with a wide range of applications.[2] Controllable growth of nanostructures is a crucial issue for nanoscale science. This relates to the self-organized growth and/or fabrication of nanostructures of desirable shape, size, and morphology. The significances of the controllability manifest in both the chemistry of small-size material synthesis and the realization of the diverse nanoscale material's applications.[3] The use of such nanostructures with tailored geometries as building blocks is also expected to play crucial roles in future nanodevices. Since the discovery of carbon nanotubes much attention has been paid to exploring the usage of inorganic semiconductor nanostructures as field-emitters due to their low work functions, high aspect ratios and mechanical stabilities, and high electrical and thermal conductivities.[4] In this report, we will introduce the controlled growth of 1D ZnS nanostructures at first, and then discuss the field-emission application for 1D ZnS nanostructures. The controlled growth including temperature-controlled and catalytic growth of ZnS nanostructures,[5] shape- and size-controlled growth of ZnS nanostructures,[6] and a simple and facile route to control ZnS junctions or heterostructures.[7] For the field-emission application of 1D ZnS nanostructures, although the work function for ZnS (7.0 eV) is larger than for Si (3.6 eV), AlN (3.7 eV), SiC (4.0 eV), C nanotubes (5 eV) or ZnO (5.3 eV), we successfully enhance their field-emission properties by making ZnS nanobelts into ultrafine structures (the width peaked at 10-20 nm)[8] or into crystal orientation-ordered ZnS nanobelt quasi-arrays.[9] Acknowledgement: These works were supported by the Japan Society for the Promotion of Science (JSPS) Fellowship. References [1] X.S. Fang et al. J. Mater. Sci. Technol. 22 (2006) 1-18. [2] X.S. Fang et al. J. Mater. Sci. Technol. 22 (2006) 721-736. [3] L.D. Zhang, X.S. Fang, C.H. Ye, Controlled Growth of Nanomaterials, World Scientific Pub Co Inc, Singapore, 2007. [4] X. S. Fang et al. J. Mater. Chem., 2008, DOI: 10.1039/b712874f. [5] X.S. Fang et al. Adv. Funct. Mater. 15 (2005) 63-68. [6] X.S. Fang et al. J. Phys. Chem. C. 111 (2007) 8469-8474. [7] X.S. Fang et al. J. Mater. Sci. Technol. 2008, in press [8] X.S. Fang et al. Adv. Mater. 19 (2007) 2593-2596. [9] X.S. Fang et al. Chem. Comm. (2007) 3048-3050.

2:45 PM E4-S3.4
The Synthesis and Structure of Silica Nanowires and Associated Gold-Silica Peapod Structures. (#1404) T.-H. Kim, Robert G. Elliman; Electronic Materials Engineering Department, Research School of Physical Sciences and Engineering, The Australian National University, Australian Capital Territory, Australia.

Silica nanowires with diameters of 50-200 nm and lengths in excess of a millimeter can be grown on silicon by metal-induced vapour-liquid-solid or solid-liquid-solid mechanisms. This is usually achieved by the introduction of a silicon precursor, such as silane, but growth has also been reported when thin metal layers are deposited directly onto a silicon wafer and annealed in nitrogen or argon. In this case it is generally argued that the growth proceeds via dissolution of silicon from the substrate, with oxygen (O₂ and/or H₂O) introduced as a low-concentration (typically <5 ppm) contaminant via the annealing ambient. In this study we demonstrate that the growth process is likely to be more subtle. Specifically, we demonstrate silica wire growth on silicon and silica substrates by the nickel or gold precipitates (produced by ion-implantation or vapour-phase deposition) and annealing at around 1100°C in nitrogen, argon and forming gas. Growth of nanowires on the silica substrates is only observed when they are in the presence of an additional uncoated silicon wafer, confirming a significant contribution to growth from vapour-liquid-solid growth mechanism. Consideration of the vapour pressures of different species suggests that the source of silicon is likely to be SiO produced by reaction between the silicon wafer and residual oxygen or water vapour in the annealing ambient. Attempts to increase the rate of growth by increasing the oxygen concentration instead terminate the nanowire growth -likely due to the formation of a continuous SiO₂ protective layer on the silicon wafer. We further show that control over the source of SiO can be used to control the location of the catalyst particle on the wire and to form Au-silica peapod structures.

3:00 PM E4-S3.5
The Effects of Electron and Hole Injection on the Photoluminescence of CdSe/CdS/ZnS Nanocrystal Monolayers. (#1442) Ann Kathleen Gooding, School of Chemistry, The University of Melbourne, Parkville, Victoria, Australia.

The photoluminescence (PL) of 2D monolayers of CdSe/CdS/ZnS semiconductor nanocrystals (NCs) deposited on gold substrates and incorporated into electrochemical cells has been studied. By combining simultaneous cyclic voltammetry and confocal microscopy it is demonstrated that when a positive potential is applied to the film in an acetonitrile electrolyte, the PL is irreversibly quenched. This is irrespective of whether the samples are under an inert atmosphere or exposed to air or water vapor. When a negative potential is applied under nitrogen, quenching is also observed; however, it is reversible. Conversely when a negative potential is applied to the NC films in aerated acetonitrile, the PL intensity increases. The enhancement of the PL is stable for at least 180 s whilst the potential is held at -1.0 V (vs. Ag quasi-reference electrode). When the potential is removed the PL intensity returns to the starting value. These results clearly indicate that photobrightening and charge carrier injection are coupled processes. We propose a simple kinetic model that explains the origins of photobrightening.

3:15 PM E4-S3.6
Ferromagnetic Contacts onto Carbon Nanotubes for Spintronics Applications. (#1399) Jose Gracio, Elby Titus; University of Aveiro, Portugal.

The realization of spintronic devices, which employ the electron's spin degree of freedom as well as its charge to store, process and transmit information have emerged as a breakthrough in electronic research . Many designs for this new class of devices has been proposed or built. Spin-polarised electrons occur naturally in ferromagnetic materials and it can be injected from a ferromagnet into a non- ferromagnet . The most common application of spin effect is giant magnetoresistance (GMR) devices and the field has expanded significantly since the discovery of the GM effect in magnetic multilayers, the main driving force leading to the development of the present generation of magnetic storage devices. In this work, we propose a spintronic system using carbon nanotubes contacted with ferromagnetic nickel. The idea is to inject spins efficiently into a non magnetic material and its subsequent transformation into large electrical signal. CNTs are ideal for spintronic devises due to their nanoscaled size, extremely long elastic- and phase-scattering lengths and it can behave as one-dimensional conductors. We have adopted a novel route to the development of ferromagnetic contacts, such as nickel (Ni) onto carbon nanotubes (CNTs) using laser powered chemical vapour deposition (LPCVD). The laser CVD process uses the precursor: nickel carbonyl- Ni(CO)4 which has a boiling point of 430C and is readily decomposed into elemental nickel and CO by laser heating at 150-200 0C.