Symposium : C
|Properties III : Paolo Scardi|
|08:30||Nanoionics: Size effects on ion transport and electrochemical storage|
Authors : Joachim Maier Max Planck Institute for Solid State Research Stuttgart, Germany
Resume : While size effects on electronic transport properties are quite well studied and led to the acknowledged field of nano-electronics, this contribution will essentially be concerned with the effects on ion transport. Mobile ions enable a palette of applications in particular in the field of energy research and cannot be rendered dispensable by using electrons. Typical examples are fuel cells and batteries. Here nano-ionics can have a substantial impact. It will be shown that by the introduction of interfaces and the variation of their spacing not only drastic changes in conductivities but also qualitative changes can be achieved: insulators can be turned into conductors, electronic conductors into ion conductors, anion into cation conductors and interstitial into vacancy conductors. The use of true size effects leads to the generation of artificial mesoscopic ion conductors. In addition to transport also storage is of direct relevance for electrochemical devices. In particular in the field of Li-batteries nano-ionics is demonstrated to be of great potential. Not only does down-sizing allow for a fast storage, also storage capacities can be severely influenced by size. Moreover the dominance of interfaces allows for a new storage mode through which Lithium is accommodated in composites by a “job-sharing” mechanism. Besides pronouncing the materials science implications, the underlying thermodynamic concepts are emphasized.
|09:00||Ion transport and storage of nanoscaled heterostructures|
Authors : Xiangxin Guo Key Laboratory of Transparent and Opto-functional Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding Xi Road, Shanghai 200050, China
Resume : Electrochemical devices based on ionic conductors are nowadays essential because of their important applications in energy conversion and storage. One of key issues in these devices is the ion transport and storage at the interfaces, especially at the nanoscaled heterogeneous interfaces in composite materials. For instance in Li-ion batteries or solid oxide fuel cells, there exists numerous heterostructures including the interfaces between electrodes and electrolytes and the intra-electrode interfaces within electrodes. These interfaces play important roles in the device performance such as energy density, power density, cycle stability and so on. However, the mechanism of interfacial effect on ion transport and storage is far from clear. This is mainly due to the materials used in the real devices having very complicated surroundings, which cause difficulties to examine the physical and chemical processes occurred at the interface. Two-dimensional heterostructures, i.e. thin films or multilayers are advantageous for fundamental investigations of the interfacial effect, which have attracted much attention recently. As a result, in this presentation we will give a review of recent progress on fundamental research of ion transport and storage at nanoscaled heterostructures. Typical interfacial effects on the ion transport and storage, especially in downsized two-dimensional multilayers or composite films will be discussed. Mechanism of manipulating transport properties through space-charge as well as microstructural effect will be addressed in detail. Moreover, some new results related to size-dependent electrochemical properties of thin-film anodes for Li-ion batteries will also be presented.
|09:30||"Dynamic Structural Behavior of Free-Standing Bismuth Nanoparticles and its Influence on their Conductance Properties"|
Authors : Debora Marchak, Denis Glozman, Ori Cheshnovsky, Yoram Selzer; Tel Aviv University
Resume : Bulk Bismuth is a semimetal with unique anisotropic electronic and crystallographic properties. Quantum confinement effects are observable at nanocrystal sizes of about 25nm and semimetal to semiconductor transition takes place in crystals of 50nm or less in size. Moreover, Bismuth nanoparticles were reported to show thermally activated structural instabilities. These phenomena introduce Bismuth as an excellent candidate for the study of dynamic quantum systems. A novel polymer-free synthetic method has been developed, which yields a colloidal stable solution of Bismuth nanoparticles with a diameter distribution ranging between 2nm and 10nm. Nanoparticles prepared by this route are ready to be structurally and electronically investigated. The dynamic structural behavior of the as-prepared resulting nanoparticles is analyzed under HRTEM and their conductance properties are probed by Scanning Tunneling Spectroscopy methods at different temperatures ranging from 80K to room temperature. The results show a clear dependence of the local density of states on the different crystallographic directions through which the transport takes place, in accordance with the unique high anisotropy of the system. In addition, the dynamic structural behavior reflects upon the conductance properties of the nanoparticles.
|09:45||Confinement effects for ionic carriers in perovskite ultrathin films|
Authors : E. A. Kotomin 1,2, D. Gryaznov 1,2, R. A. Evarestov 3, V.E. Alexandrov 4 and J. Maier 1 1)Max Planck Institute for Solid State Research, Heisenbergstr., 1, D-70569, Stuttgart, Germany 2) Institute for Solid State Physics, University of Latvia, Kengaraga str. 8, Riga LV-1063, Latvia 3) Department of Quantum Chemistry, St.Petersburg University, Stary Peterhof, Russia 4) Dept. of Chemical Eng. and Mater.Sci. and NEAT ORU, University of California, USA
Resume : We discuss the one-dimensional confinement effects through investigation, how the electronic and energetic properties of an oxygen vacancy change (in a comparison with the bulk properties) when defect is confined in an ultrathin insulating film. We have chosen SrTiO3 as a prototypical crystal for a wide class of ABO3 perovskite-structured materials with partly covalent chemical bonding and a neutral oxygen vacancy (called also the color F center) therein as a typical ionic carrier in this type of solids. The energetic confinement effects could arise due to both restricted ionic relaxation around the vacancy and localization of an electronic wave function of the defect in ultrathin films. One-dimensional confinement effects are modelled within the hybrid HF-DFT LCAO approach considering defects in the center and on the surface of ultrathin films (slabs) consisting of 3-13 crystalline planes . The effects include pronounced decrease of the defect formation energy (ca.1 eV), a much deeper defect band level and a noticeable change in the electronic density redistribution at the near-surface vacancy site with respect to that in the bulk. The calculations reveal that confinement effects are surprisingly short-range in this partly covalent perovskite; already for film thickness of 2-3 nm (and we believe, similar size nano-particles) only the surface-plane defect properties differ from those in the bulk. In particular, we predict considerable oxygen vacancy segregation towards the surface .  E.A.Kotomin et al, PCCP,2010, DOI: 10.1039/c0cp01060  V.E. ALexandrov et al, Eur. Phys. J B 72, 53 (2009).
|10:00||Coffee Break I|
|Methods I : Paolo Scardi|
|10:30||Simulation and modeling of the powder diffraction pattern from nanoparticles|
Authors : Kenneth R. Beyerlein (a,b), Bob Snyder (a), Mo Li (a), Matteo Leoni (b), and Paolo Scardi (b) (a) Department of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, USA (b) Department of Materials Engineering and Industrial Technology, University of Trento, Trento, Italy
Resume : While much of current scientific research is focused on how physical properties of nanoparticles – like strength and thermal transport – are dramatically different from their bulk form, their structural differences are also beginning to be understood in terms of diffraction. It is becoming evident that the theories and assumptions used to model the diffraction pattern line profiles from bulk materials are not always appropriate for nanoparticles. For example, the stable atomic structure of multiple twinned nanoparticles, which are composed of intersecting twin planes in a noncrystallographic symmetry, does not have an analog in bulk materials. Also, the large fraction of atoms near the surface requires the consideration of surface effects, which are commonly ignored for bulk materials. The task at hand is then to develop reliable structural models for nanoparticles, and use them to study the features imposed on their powder diffraction line profiles. Atomistic simulations like molecular dynamics have shown to be a powerful tool to simulate the atomic structure and dynamics of materials, and can be coupled with the Debye function to generate the powder diffraction pattern. The purpose of this talk will then be to outline this approach, and use it to study the diffraction pattern from realistic atomic constructions of metallic nanoparticles.
|11:00||The Use of Plasmon Spectroscopy and Imaging in a TEM to Probe Nanoscale Phenomena In Situ|
Authors : V.P. Oleshko National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
Resume : Electron beam-induced excitations in the 0–50 eV energy loss range dominated by plasmons are sensitive to valence electron states that primarily responsible for intrinsic materials properties and enable copious information on the band structure, phases, dielectric and optical properties. We show that valence EELS and energy-filtering TEM can be utilized to explore diverse nanoscale phenomena in situ. As a consequence of the universal binding energy relation, strong scaling relations exist between the volume plasmon energy and cohesive energy, elastic moduli and hardness of materials with metallic or covalent bonding. Using these relations, elastic and cohesive properties of nanoprecipitates in structural alloys under static conditions or during phase transformation and hardness of diesel engine soot nanoparticles have been evaluated. Spatially-resolved plasmon spectroscopic imaging offers possibilities to determine quantitatively and image in situ multiple physical properties at the nanoscale, establishing a new capability for material research and metrology. Trapping of particles in a liquid by a laser beam, which is refracted by the particle and transfers momentum to it, is known as optical tweezers. We demonstrate thermally assisted electron tweezers, i.e. trapping and stirring of 20-100 nm solid Al spheres by an electron beam. The particles formed inside molten opaque 100-400 nm-Al-Si eutectic alloy droplets were monitored using real-time “ball-in-ball” plasmon EFTEM.
|11:15||Evaluation of quantum confinement effect in nanocrystal Si dot layer by Raman spectroscopy|
Authors : ○Y. Mizukami 1, D. Kosemura 1, Y. Numasawa 1, Y. Ohshita 2, and A. Ogura 1 1,Meiji Univ. , 2,Toyota Tech. Inst.
Resume : Nanocrystal-Si(nc-Si) has engaged much interest because of the superior physical properties in relation to quantum confinement effects. It is very important to understand the quantum confinement effects in detail. In this study quantum confinement effect in nc-Si was evaluated by Raman spectroscopy, which allows us high-sensitive measurements. Nc-Si dot was fabricated by CVD with SiH4 and subsequential surface oxidation. The set of two process steps was iterated to lead to the nc-Si dot layer. Approximately 100-nm-thick nc-Si layer for evaluation of quantum confinement effects was prepared on a Si substrate heated at 637 by above-described processes, with the iteration frequency of 100 times. Furthermore, post-oxidation annealing was performed in the O2/H2 = 1/2000 ambient at 1050 C for 5-10 min in order to improve the crystal quality of nc-Si. The structure for the nc-Si dot layer was investigated by using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The investigation results show that the structure of the nc-Si dot was covered with oxide and their average diameter was 5-7nm. The excitation sources were UV and visible lasers in the Raman measurements. We first confirmed the dependence of Raman spectrum on laser power. As a result, there was no change in Raman spectra. This behavior indicates that the density of nc-Si was high enough for the thermal dispersion. After post-oxidation for 5 and 10 min, broadening on the lower frequency sides in Raman spectra were obtained, which were attributed to phonon confinement effect in nc-Si. Furthermore, more compressive stress was induced in nc-Si after post-oxidation for 10 min than that for 5 min. We confirm the quantum confinement effect in the nc-Si dot layer.
|11:30||Atomic scale characterization of SmCo5/Fe nanocomposites by atom probe tomography and correlation with the magnetic properties|
Authors : R. Lardé(1), J.M. Le Breton(1), D. Givord(2), O. Isnard(2), V. Pop(3), I. Chicinas(4) (1) Groupe de Physique des Matériaux, UMR CNRS 6634, Université de Rouen, 76801 Saint Etienne du Rouvray, France (2) Institut Néel, CNRS, Université J. Fourier, BP 166, 38042 Grenoble, France (3) Faculty of Physics, Babes-Bolyai University, 400084 Cluj-Napoca, Romania, (4) Materials Science and Technology Dept., Technical University of Cluj-Napoca, 400641 Cluj-Napoca, Romania
Resume : The magnetic performances of permanent magnets can be greatly improved by coupling the hard magnetic phase with a soft magnetic phase. This so-called exchange-spring coupling can be achieved through the elaboration of nanocomposite materials composed of nano-sized soft magnetic clusters embedded in a hard magnetic matrix. To obtain such a nanostructure we applied mechanical milling to synthesize SmCo5/α-Fe nanocomposites starting from a mixture of SmCo5 powder and 20 wt% of elemental iron. SmCo5/Fe nanostructured alloys were thus investigated by X-ray diffraction, 57Fe Mössbauer spectrometry, magnetic measurements and Atom Probe Tomography (APT). The APT is a 3D high resolution analytical microscope, which provides a 3D mapping at the atomic scale of the spatial distribution of atoms in the analyzed specimen. It allowed investigating the nanostructure and the chemical nature of the hard/soft phases interfaces. The results show that during the milling Co/Fe interdiffusion occurs, leading both to the formation of Fe(Co) regions and to the introduction of Fe in Sm-Co regions. Annealing the as-milled samples leads to a structural refinement and promotes the introduction of more Co in Fe-rich regions, and more Fe in Sm-Co regions. This induces the homogenisation of the α-Fe(Co) regions and the formation of a Sm(Co,Fe)5 phase. Both coercivity and remanence depend upon the processing conditions and can be improved by adjusting the milling and/or heat treatment conditions (time and temperature). The strong Co/Fe interdiffusion may reinforce the exchange interactions between the hard Sm(Co,Fe)5 and the soft α-Fe(Co) phases.
|11:45||Coherent scattering condition in nanocrystalline systems|
Authors : L. Gelisio and P. Scardi Dept. of Materials Engineering and Industrial Technology, University of Trento, Italy
Resume : Nanocrystalline thin films and, more rarely, powders sometimes show interference effects leading to some degree of coherence in the diffracted signal from adjacent domains [see 1,2 and references therein]. Understanding this behaviour is important to properly determine microstructural properties of interest in the studied nanocrystalline system, and also clarifies some basic, qualitatively known features of powder diffraction. For example, the long debated distinction between crystalline domain or crystallite and what is considered in other cases a grain, e.g., in electron microscopy. The present work exploits the capability of atomistic simulations to build ideal systems of nanocrystals with known shape, size and misorientation among different domains; profiting of the great potential of parallel computation on GPUs , the Debye equation is used to generate corresponding powder patterns to be analysed by state of the art powder diffraction methods.  D. Rafaja, V. Klemm, G. Schreiber, M. Knapp and R. Kuzel, J. Appl. Cryst. (2004) 37, 613-620.  K.R. Beyerlein, R.L. Snyder, M. Li, P. Scardi, Phil. Mag. (2010) 90, 3891-3905.  L. Gelisio, C.L. Azanza Ricardo, M. Leoni, P. Scardi, J. Appl. Cryst. (2010) 43, 647-653.
|Methods II : Jeff de Hosson|
|13:30||In-situ powder diffraction experiments on nanocrystalline NiFe|
Authors : J. Zimmermann , S.Van Petegem , M. Legros [29, X. Sauvage , H. Van Swygenhoven   Materials Science and Simulations, NUM/ASQ, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland  CEMES-CNRS, 29 rue J. Marvig, 31055 Toulouse, France  University of Rouen, CNRS UMR 6634, Groupe de Physique des Matériaux, Faculté des Sciences, BP12, 76801 Saint-Etienne du Rouvray, France
Resume : In crystalline metals the grain size plays a key role in the mechanical response of the material. The strengthening of the material with decreasing grain size is well described by the Hall-Petch relation until a grain size of 100nm and even lower. Deformation mechanisms in coarse grained metals are based on a dislocation mechanism where dislocations are created during deformation with their propagation and multiplication being an essential mechanism for the resulting ductility and strength. However with decreasing grain size a transition is to be expected towards plastic mechanisms involving grain boundaries (GB). Several molecular dynamic simulations studies suggested that at small grain sizes single dislocations are generated at the GBs then propagate through the grain and are finally absorbed at the opposing GB without leaving debris in the grain interior. In order to investigate the plastic deformation mechanisms of nanocrystalline metals we have developed an in situ synchrotron x-ray-diffraction technique which allows the simultaneous measurement of many diffraction peaks continuously during mechanical testing (tensile and compression), providing a direct link between the evolving microstructure and the macroscopic mechanical data (Rev. Sci. Instr. 77 (2006) 013902). Here we report the study of plastic deformation of electrodeposited Ni-Fe with a Fe fraction of 50% and a grain size close to 10nm. The behavior of nanocrystalline Ni-Fe is compared with the one of nano
|14:00||Non-monotonic lattice parameter variation with crystallite size in nanocrystalline ball milled powders.|
Authors : Gayatri Rane , Udo Welzel, Eric Mittemeijer Max Planck Institute for Metals Research, Stuttgart, Germany. Institute for Materials Science, University of Stuttgart, Germany.
Resume : Pure metal powders (Ni, Fe) studied in this work have been subjected to ball milling and subsequent anneals in order to achieve nanograined material with varying crystallite size. Accurate determination of the lattice parameter by X-ray diffraction has been performed on the powder samples; the reflection positions have been corrected for instrumental as well as microstructural effects (stacking faults). X-ray diffraction line profile analysis has been used to determine the microstructural parameters, such as crystallite size and defects. The microstructural investigations have been complemented by transmission electron microscopy. An anomalous dependence of the lattice parameter on the crystallite size has been observed for both ball milled Ni and Fe: lattice contraction followed by lattice expansion with decreasing crystallite size. The non-monotonic changes have been proposed to be an effect of competing mechanisms: interface stress induced contraction versus magnetic multi-domain to single-domain transition occurring at about the crystallite size value where a minimum value for the lattice parameter is observed. Another proposal put forward (W. Qin et al. J. Phys.: Condens. Matter 19 (2007) 236217) is based on the combined effects of interfacial stress induced compression and lattice expansion due to excess volume in the grain boundaries. This model has been fitted to our data and could as well explain the observed non-monotonic change at a critical grain size.
|14:15||Measuring and modelling the mechanical stress transmitted by Silicon Nitride lines on Silicon substrates|
Authors : P. Benzo 1, S. Reboh 1, M. J. Hÿtch 1, R. Cours 1, P. Morin 2, A. Halimaoui 2, D. Bensahel 2 and A. Claverie 1 1) Groupe nMat, CEMES-CNRS, Université de Toulouse, 29 rue J. Marvig, 31055 Toulouse, France 2) ST Microelectronics, 850 rue Jean Monnet, F-38926 Crolles Cedex, France
Resume : Strain engineering is the state-of-the-art technique to enhance the performance of MOSFET devices by increasing carriers’ mobility. Several methods have been proposed to achieve this objective however, there is an increasing interest in using inherent steps of devices processing for that purpose, such as the deposition of Silicon Nitride (SiN) contact etch stopping layers (CESL). Such SiN layers can exhibit large intrinsic stresses which are then transmitted to the active region of the device. In general, these layers are chemically unstable when deposited and evolve structurally and chemically during further processing of the device. Moreover, the complex geometric structures of the devices also significantly affect the resulting strain distribution. Consequently, the mechanical characteristics of the ensemble evolve during processing and are difficult to measure at the pertinent, nanometer, scale. In this work, we have studied the transmission of stress within a Si wafer resulting from the deposition of tensile stressed SiN lines of different widths and spacings using the dark-field electron holography technique (HoloDark) we have recently invented. In parallel, we have developed finite elements simulations to understand the origin of the measured strains and deduce the characteristics of the ensemble, evidencing possible proximity effects. This work is the first step towards the characterization and modeling of more complexes structures such as real devices.
|14:30||Near-field optical measurement of the size-dependent dielectric function of single tungsten nanowire|
Authors : M. Kazan(1), Z. Sedaghat(2), A. Bruyant(2), J. Vaillant(2), S. Blaize(2), P. Morin(3), and P. Royer(2) 1-Department of Physics, American University of Beirut, Riad El-Solh 1107 2020, Beirut, Lebanon 2-Laboratoire de Nanotechnologie et d'Instrumentation Optique - Institut Charles Delaunay - Universit?e technologie de Troyes - CNRS FRE 2848, 12 rue Marie-Curie BP2060 10010 TROYES, Cedex France 3-ST Microelectronics, Crolles, France
Resume : While intensive research works have been dedicated to the investigation of the size-dependent electronic confinement and its effect on the dielectric properties of nanostructured materials, there is still a lack of information on the size-dependent phonon confinement and the related dielectric properties. Such information would be crucial to gain insight into the effect of size on the harmonic and anharmonic terms of the interatomic forces and rationally tailor novel nanoscale materials for efficient technological applications. In this communication we tackle this issue and present an experimental analysis of the size-dependent complex dielectric function in the mid-infrared spectral range for free standing tungsten (W) nanowires of diameters exceeding the Bohr radius (rB). By this way we prevent the electronic confinement and we enhance the contribution of the confined phonon system to the overall optical response of the nanowire. The scattering-type scanning near-field optical microscopy (s-SNOM) has proven its strong ability to recover the chemical fingerprint of materials at a nanometer scale due to its intrinsic sensitivity to the local dielectric function. Thus, in the infrared spectral range, this experiment appears to estimate eventual modifications of the sample or probe dielectric parameters related to phonon confinement. Therefore, we have performed mid-infrared near-field experiments using tungsten (W) nanowires of different diameters as nanoprobes. The samples scanned with the W probes were carefully designed flat surface gratings of copper lines spaced by 6 μm and embedded in intrinsic silicon in order to obtain a clear metal/dielectric contrast free of topographical artifacts. When the bulk mid-infrared dielectric parameters of W are considered, all the existing electromagnetic models predict a noticeably higher signal on the metallic structure compared to the dielectric. Our experimental results are in perfect agreement with the theoretical prediction when relatively large diameter W probe is used. However, our experimental results showed that with decreasing the W probe diameter the contrast between the metallic and the dielectric region weakens until a reverse signal contrast occurs. A phenomenological model as well as Green’s technique based model strongly suggests that the experimentally observed dependence of the probe diameter on the signal contrast must be due to a modification of the infrared complex dielectric function of the W probe that occurs because of the phonon confinement. For a small enough diameter, the dielectric function of W behaves as a nonmetal dielectric function and presents a strong anisotropy and material polarity signatures although W is a metallic nonpolar isotropic material. A physical model based on the elasticity theory is used to interpret such a dramatic modification in the nature of the W infrared complex dielectric function.
|14:45||Advances in nanoparticle probes for coherent two-photon microscopy|
Authors : Marcin Zielinski (a,b), Shoshana Winter (c), Dan Oron (b,c), Dominique Chauvat (a,b), Joseph Zyss (a,b) a) LPQM, Ecole Normale Supérieure de Cachan, Cachan, 94230 CEDEX, France. b) D’Alembert Institute, Laboratoire Européen Associé NABI,CNRS-Weizmann. c) Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, 76100, Israel.
Resume : The SHG detection size barrier of ~40 nm at the single nanoparticle scale has been successfully surpassed, by considering the two-photon resonant excitation in individual zinc-blende CdTe quantum dots (QDs), in order to find an alternative nonlinear system of comparable size as a fluorescent nanolabels. Single CdTe QDs of about 12.5 nm diameter provide efficient coherent SHG radiation, as high as 100 kHz, furthermore exhibiting remarkable sensitivity to spatial orientation of the crystalline lattice. Moreover, quantum confinement effects have been found to strongly contribute to the second-order nonlinear susceptibility features. Herein, we present our results on quantitative characterization of the χ(2) of QDs by way of their spectral dispersion and size dependence. Single particle spectroscopy and ensemble HRS studies prove that under appropriate conditions, χ(2) of quantum confined structures can significantly exceed that of bulk. Furthermore, a novel type of semiconducting hybrid rod-on-dot (RD) QDs is engineered by building up crystalline moieties with different symmetries, in order to increase their quadratic nonlinearity while maintaining their size close to a strong quantum confinement regime. Significant SHG enhancement is observed exceeding that of mono-compound QDs, due to a coupling between two nonlinear materials and slower decoherence, which we attribute to the induced spatial charge separation upon photoexcitation.
|15:00||Optical Sensing Based on Surface Plasmon Coupling in Three Dimensional Nanoparticle Arrays|
Authors : R. Morarescu (1), B. Kolaric(1), P. Damman (1), R. A. L. Vallée (2), W. Libaers (3), K. Clays (3) (1) Laboratoire Interfaces & Fluides Complexes, Centre d' Innovation et de Recherche en Matériaux Polymères, Université de Mons, 20 Place du Parc, B-7000 Mons, Belgium. E-mail: firstname.lastname@example.org (2) Centre de Recherche Paul Pascal (CNRS-UPR8641), 115 avenue du docteur Schweitzer, 33600 Pessac, France. (3) University of Louvain, Dept. Chem, B-3001 Louvain Belgium.
Resume : Metal nanoparticles have been widely explored for different applications that use their superior optical properties based on localized surface plasmon (LSPR) resonance. In this work we present recent results for surface plasmon coupling enhanced dielectric environment sensitivity in three dimensional gold nanoparticle arrays. The optical properties of such arrays were tuned in a wide spectral range from UV-visible to near-IR by changing the nanoparticle size and interparticle distances, and compared with isolated nanoparticle spectra. The corresponding sensing efficiency has been experimentally confirmed and numerically simulated for all used combinations of nanoparticles sizes and interparticle distances. This novel approach of using plasmon coupling in three dimension array for optical sensing should have a large impact in nanotechnology and is a promising route for future applications.
|15:15||A Novel Approach to Determine Metallic Nanoparticle Size Using Conduction Electron Paramagnetic Resonance|
Authors : Brian J. Simonds (1,2), Archana Subramaniyan (2,3), Ryan O'Hayre (2,3), P. Craig Taylor (1,2) (1) Physics Department, Colorado School of Mines, Golden, Colorado USA (2) Renewable Energy Materials Research Science and Engineering Center, Colorado School of Mines, Golden, CO 80401 USA (3) Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO 80401 USA
Resume : A novel technique for determining the size of metallic nanoparticles incorporated into proton conducting ceramics is demonstrated using conduction electron paramagnetic resonance (CEPR). The resonances associated with palladium (Pd) nanoparticles in yttrium doped barium cerate (BaCe0.8Y0.2O3-δ) are identified and studied as a function of temperature. As the CEPR lineshape changes with temperature, the temperature at which the skin depth of the microwave (~9.5 GHz) radiation is the approximate size of the palladium nanoparticles is clearly identified. This identification, in conjunction with data on the temperature dependence of the skin depth and the electron mean free path in Pd metal, allows for an approximate determination of nanoparticle size. This size is estimated to be about be about 50 nm in this particular system. Supporting electron microscopy data are also presented, but this new technique has an obvious advantage because it is a non-destructive, bulk measurement that can resolve nanoparticle sizes that are difficult to obtain using other techniques. It is anticipated that this technique has great applicability for determining the nanoparticle size in any material system where metallic nanoparticles are incorporated into a non-conducting matrix. In addition, other paramagnetic defects found in the BaCe0.8Y0.2O3-δ EPR spectrum are identified and discussed.
|Poster III : to be announced|
|16:00||Self-assembly of Ge quantum dots and voids in an alumina film|
Authors : M. Buljan1, S. R. C. Pinto2, A. G. Rolo2, J. Martín-Sánchez2, J. Grenzer3, A. Müecklich3, S. Bernstorff4, M. J. M. Gomes2, 1 Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia 2 Centre of Physics and Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal 3 Forschungszentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden, Germany 4 Sincrotrone Trieste, Basovizza, Italy
Resume : The production of regularly ordered lattices of quantum dots (QDs) or voids is of great interest due to their amazing properties and many relevant technological applications. However, the knowledge about the production of regularly ordered structures in amorphous matrices is very limited. We demonstrate a self-assembled growth of a three-dimensional well ordered Ge QD lattice, in a single 0.5 micron thick layer, during magnetron rf-sputtering deposition of a Ge+Al2O3 mixture at an elevated substrate temperature . A well ordered three-dimensional body centered tetragonal QD lattice within the whole deposited volume is obtained. The parameters of the lattice can be tuned by changing the deposition parameters. The observed self-assembly of QDs is explained by diffusion mediated nucleation and surface morphology effects, and it is simulated by a kinetic Monte Carlo model. Surprisingly, during subsequent thermal treatment of those films the germanium atoms were lost from the film by out diffusion, and ordered void lattices were formed replicating the ordered Ge QDs structure present before the annealing . The formed QDs or voids are very small in size (less than 4.0 nm), have a narrow size distribution and a very dense packing density, which are excellent features for applications in nanotechnology.  M. Buljan, et al., PRB 82 (2010) 235407/ doi: 10.1103/PhysRevB.82.235407  S. R. C. Pinto, et al., APL 97 (2010) 173113 / doi:10.1063/1.3499426
|16:00||Synthesis and properties of titania microspheres consisted of nanoparticles with high specific surface area|
Authors : Smirnov E.A., Matveeva M.A., Chelpanov V.I., Garshev A.V.
Resume : Titanium dioxide-based materials are materials of interest because of their application in photonic crystals, catalysis and photocatalysis. One of promising applications is solid state for high-performance liquid chromatography (HPLC). Materials based on titania are more suitable for HPLC than silica and polystyrene, because titania has porous surface and extensive pH operating range. For this application monodisperse globe-shaped particles 1-5 μm in diameter with good mechanical properties are also required. In this work we develop cheap and simple method based on controllable hydrolysis of titanium alkoxide in ethanol to prepare spherical particles up to 1,5 μm in diameter with narrow size distribution for HPLC with following surface modification via hydrothermal treatment. As-prepared microspheres consist of nanoparticles with mean diameter 10 nm and possess high specific surface area up to 220 m2/g. Hydrothermal treatment leads to increase diameter of nanoparticle (up to 30 nm) and reduce specific surface area down to 120 m2/g. Also we investigate mechanical properties of microspheres via atomic-force microscopy and compare with commercially available material of sorbents for HPLC (silica microspheres) and refine the area of pH-stability for titania microspheres (pH ranging from 2 to 14). Titania particles after hydrothermal treatment demonstrate higher spring constant than silica and extremely high chemical stability in wide pH range.
|16:00||Correlation between structural and electrical properties of MOS structures based on Ge nanocrystals embedded in SiO2 grown by RF- magnetron sputtering|
Authors : S. Levichev*, E. M. F. Vieira*, J. Martín-Sánchez*, O. Karzazi**, A. Chahboun*,**, M. Buljan***, S. Bernstorff****, and M. J. M. Gomes* * Physics Department, University of Minho, 4710 - 057 Braga, Portugal ** Physics Department, Faculty of Sciences, BP 1796, Fes, Morocco *** Rudjer Boskovic Institute, Bijenicka 54, 10000 Zagreb, Croatia **** Sincrotrone Trieste, 34012 Basovizza, Italy
Resume : In recent years semiconductor nanocrystals (NCs) have attracted a strong attention due to their size-dependent optoelectronic properties. Ge nanostructures embedded in dielectric matrices have been a subject of huge interest due to their potential applications in nanoelectronics and optoelectronics, as well as in floating gate memory structures . The distribution of NCs and their structural properties dramatically affect the performance and reliability of the NCs based devices. In these frames an investigation of the correlation between structural and electrical properties is an important task. Metal–oxide–semiconductor structures with Ge NCs embedded in SiO2 thin films on p-Si(100) substrates were fabricated by the RF- magnetron sputtering technique at room temperature with subsequent rapid thermal annealing in nitrogen atmosphere. Depth profiling of the Ge distribution inside the MOS structures was done by X-ray photoelectron spectroscopy. The lateral size, shape and distribution of the Ge NCs in silica matrix were investigated by means of grazing incidence small angle X-ray scattering (GISAXS). Current - Voltage and Capacitance - Voltage measurements were performed in order to study their electrical properties. The results indicate a strong variation of the memory effect relatively to the structural properties.  S. Duguay, J. J. Grob, A. Slaoui, Y. Le Gall, and M. Amann-Liess. J. Appl. Phys. 97 104330 (2005).
|16:00||Characterization of CNT dispersion in polymer matrices by combined microscopic methods|
Authors : B. Pataki, Z.E. Horv?, L.P. Bir?esearch Institute for Technical Physics and Materials Science, H-1525 Budapest, P.O. Box 49, Hungary http://www.nanotechnology.hu/
Resume : Carbon nanotube (CNT)-filled polymer composites conquer more and more space in applications due to their unique mechanical, thermal and electrical properties. The degree of CNT dispersion in the matrix is one of the main factors determining the quality of the material. Because of their tiny size, optical microscopy (OM) methods are not directly suitable for characterization of CNT and its distribution in composites. Transmission Electron Microscopy (TEM) has the potential of it but that is too costly and time consuming for characterization in routine materials development. Present work investigates the possibilities of developing a method for the quick characterization of the CNT dispersion in different transparent matrices based on transmission OM. For this, we performed comparative TEM and OM analysis of composites to determine correlation between structural parameters and image features recorded at different size scales.
|16:00||Graphenes proprieties obtained from Graphite and Graphite Oxides|
Authors : Ioana Ion 1 2, Alexei Zubarev 1, Ana Cucu 1, Adriana Andronie 1, Stefan Iordache 1, Serban Stamatin 1, and Ioan Stamatin 1 1 University of Bucharest, Faculty of Physics, 3Nano-SAE Research Centre, P.O.Box MG-38, 077125 Magurele, Romania 2 Carbon Materials Laboratory , National Institute for Research and Development in Electrical Engineering, ICPE-CA, 030138 Bucharest-3, Romania
Resume : Graphite and graphite oxides (GOX) were used as starting material to graphene synthesis by three experimental methods: graphite exfoliation via surfactant-water solution; Hummers modified method, followed by GOX reduction to graphene with hydrazine and the third method, GOX reduced using water near to supercritical point. The graphenes were characterized by UV-Vis, XRD, FTIR and Raman Spectroscopy, DLS, SEM and AFM. Bulk electrical conductivity was measured function of pressure perpendicular on the graphene plane. Each synthesis method leads to different properties which make graphenes appropriate for different application covering supercapacitors, nanocomposites or electronic devices. The reduction near supercritical condition rises to high quality single layer of graphenes.
|16:00||Confinement effects in Au-Pd nanoalloy clusters and wires encapsulated in carbon nanotubes|
Authors : Beien Zhu (1), Ivailo Atanasov (1), Yuexia Wang (2,3), Marc Hou (1) 1. Université Libre de Bruxelles CP 234, Bd du Triomphe, B-1050 Bruxelles, Belgium 2 .Applied Ion Beam Physics Laboratory, Fudan University, Key Laboratory of the Ministry of Education, China 3 .Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433, China
Resume : Equilibrium configurations of icosahedral Au-Pd nanoalloy clusters (AuPd55 and AuPd147) and of a 130 atoms AuPd nanowire segment are studied at 100K over the whole composition range from pure Pd to pure Au by Metropolis Monte Carlo importance sampling. The effect of size on phase stability, ordering and segregation states are compared between situations where these systems are free standing or encapsulated in carbon nanotubes (CNT). Two armchair CNTs,(12, 12) and (15, 15), provide suitable encapsulation spaces. An embedded atom model is used for intermetallic interactions, the Brenner potential for C-C interactions and Lenard Jones potentials for the metal-carbon interactions. Stable phases are identified in the icosahedral clusters corresponding to well-defined structural ordering. The nanowire segment displays no significant phase stability, although ordered Au-Pd arrangements could be identified. As an effect of the presence of interface between the CNT and the clusters, their thermodynamic stability is reduced and a cylindrical symmetric chemical ordering is induced for some stoichiometries. The CNTs are found to favour Pd surface segregation while Au segregation is found at the surface of the free standing systems. Temperature and size effects are briefly discussed.
|16:00||Precipitate strengthening of nano-structured aluminium alloy|
Authors : Kinga Wawer, Malgorzata Lewandowska, Krzysztof J. Kurzydlowski Warsaw University of Technology Faculty of Materials Science and Engineering, Woloska 141, 02-507 Warsaw, Poland
Resume : The major microstructural elements influencing the properties of metals and alloys are the constituent grains and precipitates. Refinement of the grain size to the nanometre scale brings about a significant increase in the mechanical strength of the materials because the increased number of grain boundaries provide more obstacles to dislocation movement. A similar effect is obtained if nanoscale precipitates are uniformly distributed in a more coarsely grained matrix. The development of nano-grain sized alloys raises the important question of whether precipitate strengthening is effective in nano-structured materials. In the reported work, hydrostatic extrusion (HE) was used to produce nano-structured 7475 aluminium alloy. Nano sized precipitates were induced by subsequent annealing in order that the synergic effect of both grain size refinement and precipitate hardening could be determined. It was found that the combination of low temperature annealing after HE processing led to a significant increase in the (HV0.2) microhardness from 160 to approximately 200. Moreover, the mechanical strength can be only improved by low temperature annealing treatment (at the temperature 100oC). The results are discussed in terms of precipitation process in nano-crystalline materials.
|16:00||Rapid hydrogen kinetics in Mg triggered by small Nb clusters|
Authors : C. Maurizio1, R. Checchetto2, A. Miotello2 1 Physics Department, University of Padova, Italy 2 Physics Department, University of Trento, Italy
Resume : To accelerate the slow H2 sorption kinetics of Mg a catalyst, typically in form of metal or metal oxide nano-particles, is dispersed in the matrix, favouring the metal to hydride (and reverse) phase transition. It has been shown that 10-20 nm Nb clusters in Mg act as efficient catalyst for H kinetics; however, Nb-doped Mg films needs several H-sorption cycles before the kinetics reaches a stationary condition and the hydrogen desorption process is much faster in the first few cycles than in stationary conditions. This last result is surprising because, upon activation, the Mg matrix undergoes to a progressive fragmentation which should promote a more rapid H2 sorption kinetics. We have investigated by extended x-ray absorption fine structure spectroscopy the local site of Nb in Nb-doped Mg films; upon repeated hydrogen sorption cycles leading to the sample activation we observed a progressive decrease of the Nb-Mg correlation accompanied by Nb aggregation with a progressive increase of the Nb cluster size. The Nb aggregation process was correlated with the evolution of the H2 desorption kinetic. The decrease of the H2 desorption velocity, is related with the increase of the Nb cluster size. The comparison between the samples with different additive content indicates that the optimal desorption kinetics are obtained when Nb aggregation gives rise to small Nb clusters well dispersed in the MgH2 matrix.
|16:00||Calculation of free energies of copper nanoclusters|
Authors : Antti Kuronen, Antti Paajanen, Eero Kesälä, Kai Nordlund, Department of Physics, University of Helsinki, Finland
Resume : The equilibrium structure of nanoclusters is commonly estimated by calculating the potential energies of various structural motifs of clusters. When studying the system in finite temperature, however, the thermodynamic free energy must be used. Furthermore, kinetic effects in the cluster formation process may result in structures not corresponding to the ground state. In this work we have calculated the free energy of copper nanoclusters of sizes 20-6500 atoms and different structures (fcc, icosahedral, and decahedral) in the temperature range 0-600 K. Free energies were calculated by computing the vibration density of states of the clusters in the harmonic approximation. Anharmonic effects were taken into account by an effective Gruneisen parameter. The results show that the cluster size where the equilibrium structure changes from icosahedral to fcc increases when the temperature is raised. This results is analyzed based on the vibrational properties of the different structures. In addition to perfect cluster shapes, the results of crystallization simulations of melted copper nanoclusters in Ar atmosphere were analyzed in order to shed light on the role of thermodynamics and kinetic effects in the cluster structure.
|16:00||Rational fabrication of 2-D nanoporous graphene using an anodic aluminum oxide etching mask|
Authors : Jeong-Mi Lee1,3 , Jae-Hyun Lee1,2,3, Jong-Cheol Lee1,2,3, Sung Woo Hwang3,4, Dongmok Whang1,2,3* 1School of Advanced Materials Science and Engineering, 2 SKKU Advanced Institute of Nanotechnology Sungkyunkwan University, Suwon 440-746, Korea, 3Research Center for Time-domain Nano-functional Devices, Korea University, Seoul 136-701, Korea, 4School of Electrical Engineering, Korea University, Seoul 136-701, *email@example.com
Resume : Recently graphene has attracted much interest due to their novel physical properties and potential applications in nanoelectronics. However, lack of bandgap in large-area single-layer graphene is significant hurdle to overcome. In the past few years several methods have been attempted to open and tune a bandgap in graphene. For example, Bai et al. reported fabrication of a “graphene nanomesh”, which can open up a band gap of graphene. Here, we report a facile method to pattern a monolayer graphene into 2-dimensional (2D) nanoporous structures using thin anodic aluminum oxide (AAO) film as an etching mask. The electronic properties of the nanostructured graphene have been systematically controlled by adjusting the pore structure of AAO template.
|16:00||Ultra-small TiO2 nanoparticles formed by atomic layer deposition on carbon nanotubes for photocatalysis|
Authors : Sheng-Hsin Huang1, Chi-Chung Kei2, Chih-Chieh Wang1, Yang-Chih Hsueh1, and Tsong-Pyng Perng1,3,4 1Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan. 2Instrument Technology Research Center, National Applied Research Laboratories, Hsinchu 300, Taiwan. 3Department of Chemical Engineering and Materials Science, Yuan Ze University, Chungli 320, Taiwan. 4Fuel Cell Center, Yuan Ze University, Chungli 320, Taiwan.
Resume : Recently, extensive effort in understanding the fundamental process and in enhancing the photocatalytic efficiency of semiconductors for water splitting has been made by many fields of researchers. Carbon nanotubes (CNTs) have many excellent properties to be used as support material to grow all kinds of catalyst. For example, the specific surface area, electron conductivity, thermal stability, and adsorption capacity of CNTs are better than those of activated carbon. The unique semiconducting, semimetallic, or metallic property of CNTs determines the characteristics of heterojunction of catalyst-support interface. In the present study, ultra-small TiO2 particles with different particle size were deposited on multiwall carbon nanotubes (MWCNTs) by atomic layer deposition (ALD). They were further doped with nitrogen by pure NH3 gas. The saturation growth rate of TiO2 was about 0.55 Å/cycle on acid treated MWCNTs with sufficient pulse time for TiCl4 and H2O precursors. The as-prepared TiO2 had an anatase phase, and the rutile phase of TiO2 was obtained by heating at 800 oC. The doping of TiO2 with nitrogen could be achieved in NH3 atmosphere at 500 to 600 oC.
|16:00||Magnetic properties of cobalt ferrite nanoparticles synthesized by soft chemistry route|
Authors : Charlotte Vichery, Isabelle Maurin, Jean-Pierre Boilot and Thierry Gacoin Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique-CNRS, 91128 Palaiseau Cedex
Resume : Magnetic particles of iron oxides with diameter in the nanometer range are of great interest because of their unique magnetic properties which pave the way to various applications in bio- and nano-technologies (hyperthermia for cancer treatment, MRI contrast agents, information storage…). To tune their magnetic properties, we investigated the influence of post-synthesis thermal treatments on 11 nm cobalt ferrite nanoparticles. The particles were first embedded in a non reactive and refractory silica matrix synthesized by room temperature sol-gel method. This matrix was found to prevent the particles from coalescing and reduce their growth during annealing, even at 1000°C. Such a strategy allowed us to unravel the influence of structural and chemical rearrangements on the magnetic properties at fixed particle size. The evolution of the saturation magnetization and of the coercive field will be here discussed on the basis of cation redistribution and surface state changes. Tuning the dilution of the nanoparticles within the matrix was also used to investigate the influence of magnetic dipolar interactions. The most striking result of this study is the large increase in coercitive field (up to 1.78T) which was observed for heat treatments at temperatures higher than 400°C.
|16:00||Optimization of chemical displacement deposition of copper on porous silicon|
Authors : Bandarenka Hanna1, Sergey Redko1, Nenzi Paolo2, and Balucani Marco2, 1Belarussian State University of Informatics and Radioelectronics, Microelectronic Department, P. Brovka 6, 220013 Minsk, Belarus 2 University “Sapienza” of Rome, Electronic Department, Eudossiana 18, 00184 Roma, Italy
Resume : Copper (II) sulfate was used as a source of copper to achieve uniform distribution of Cu nanoparticles (NPs) decorated on mesoporous silicon (PS). Pristine PS layers were obtained by an electrochemical anodization of Si wafers in a mixture of HF acid, isopropyl alcohol and distilled water. A simple, cheap and effective method of one-step impregnation was followed to produce copper NPs on PS. In the present work well known wet chemical displacement technique was innovated by introducing of hydrofluoric acid in solution for copper deposition. The copper-treated PS samples were characterized by SEM and XRD analysis. PS outer surface and pore walls were found to be well decorated by copper NPs inherited crystal orientation of Si planes. Simultaneously PS skeleton was observed to dissolute during copper solution impregnation step. To estimate Cu NPs dimensions Feret’s analysis of SEM pictures was used. By varying the PS formation and Cu impregnation regimes copper NPs of 2...110 nm can be obtained. Moreover principally different nanosized objects from PS covered with separated or coalesced Cu NPs to porous copper membranes were formed in that way. Electrical properties of such structures were studied by I-V characterization. It was found variation of PS preparation regimes allows creating both the rectifying and the ohmic copper/porous silicon contacts. Crystallographic orientation of the initial Si and PS porosity were revealed to strongly effect on resistance of mentioned contacts. Finally free standing mesoporous silicon layer was converted into flexible porous copper film (membrane) by displacement method. Thickness of metallic membrane reached to 20-50 m and its electrical conductivity was equal to 60-70% of bulk copper. Two porous copper films were used as electrodes for supercapacitance with liquid electrolyte. Three orders of magnitude increase of capacitance for porous copper electrodes was experimentally measured as compared with flat nonporous electrodes.
|16:00||Hexagonal-pyramidal nanoislands gold on the silicon surface|
Authors : V. L. Karbivskyy, V. V. Vishnyak , N. A. Kurgan G. Kurdyumov Institute for Metal Physics, National Academy of Sciences
Resume : Using the method of high-resolution scanning tunneling microscopy, studied the formation of hexagonally pyramidal structures of gold on the surfaces of silicon single crystal Si (111) and Si (110) after thermal spraying. For a plane of silicon (110) observed only hexagonal monolayer formation. The mechanism of formation of hexagonal-pyramidal structures of gold due to inhomogeneities of the density of electronic states, which grows on the edge of each monolayer plane. In view of the extreme atoms layer have a higher energy state, the growth of each successive layer is not starting from the edge, but from a distance of ~ 3 nm from the edge, which is determined by the relaxation of inhomogeneous electron density of states at this characteristic distance and determines the pyramidal structures.
|16:00||Aligned carbon nanotubes films synthesis and their gas sensing application|
Authors : Marjorie David, Madjid Arab*, Frédéric Guinneton and Jean Raymond Gavarri Université du Sud Toulon – Var, IM2NP, UMR CNRS 6242, BP 20132. F 83 957 LA GARDE – France
Resume : Nanomaterials and more particularly carbon nanotubes (CNTs) have attracted great interest due to their new properties and large potential applications. Carbon nanotubes present a high interest in relation with their anisotropic (cylindrical) configurations. The assembly of these nanostructures on planar substrates is crucial for design of nanoscale devices with controlled size and morphology. The Catalytic Chemical Vapour Deposition (CCVD) synthesis seems to be a promising growth method due to its high purity, simple configuration and flexibility in adjustment of the influential parameters such as temperature, flowing gas carriers and precursor liquid composition. In this work, we report the investigation on the growth of Multi Walled Carbon Nanotubes (MWNTs) obtained by CCVD method and their gas sensing application. Carbon nanotubes samples are either prepared and/or collected on the reactor walls and/or deposited on different substrates. The as-prepared materials have been characterized by means of Scnning and Transmission Electron Microscopy (SEM and TEM). The SEM and TEM images show the formation of films constituted of aligned carbon nanotubes, perpendicular to the oxide substrate. The carbon materials (powder and thin film) were also analyzed by X-ray diffraction. In addition to the presence of carbon identified as graphite phase, we have observed traces of an iron oxide identified as hematite (Fe2O3). A key parameter used in our experiment for controlling the growth of nanotubes is argon gas flow carrier rate. As a function of argon flow rate, we have obtained different states of surfaces. With gas flow rates of 1 L/h, the nanotube layers present uniform surfaces; however, for increased rates (>1 L/h), the surface changes. In this case, we have observed several growth shapes with a major population of flowers, but also scrapings with openings on the cross shape. Porous films were generated after deposition. Carbon nanotubes sieves have been obtained: they can play the role of sensitive layers with high specific area, which could be ideal for gas sensor applications. Such a configuration could favor and control the diffusion of specific gas molecules. This property is very important for improving the sensitivity and response time. Then the electical gas response of the materials is investigated. The obtained results indicate that the as prepared carbon nanotubes could exhibit good sensing properties
|16:00||Size effects in heterogeneous systems with nanoscale particles|
Authors : V.V. Levdansky, Heat and Mass Transfer Institute NASB, 15 P. Brovka Str., 220072 Minsk, Belarus, J. Smolik, V. Zdimal, Institute of Chemical Process Fundamentals AS CR, v.v.i., Rozvojova 135, 165 02 Prague 6, Czech Republic
Resume : It is known that many processes in heterogeneous systems with nanoscale particles are characterized by some specific features. In particular, the physicochemical processes occurring in aerosol systems with nanoparticles and in aerosol particles themselves in the general case depend on the particle size. The influence of the size effects on the physicochemical processes in the aforesaid systems is studied theoretically. Such processes as homogeneous nucleation in a gas and condensed phase, trapping of vapor and impurity molecules (atoms) by nanoparticles, coalescence of nanoparticles and chemical reactions inside nanoscale particles are considered taking into account the size effects. It is shown that the influence of the size effects on the above-mentioned processes can be related to a change both the sticking (condensation) coefficient of gas molecules incident on the particle surface and the vacancy concentration in nanoparticles with a reduction in the particle size. This work was supported by GAAVCR projects IAA400720804, IAA200760905 and GACR project 101/09/1633.
|16:00||Structure-color-species correlation in photonic nanoarchitectures occurring in butterfly scales|
Authors : L. P. Biró, G. Piszter, K. Kertész, Z. Vértesy, Research Institute for Technical Physics and Materials Science, H- 1525 Budapest, POB 49, Hungary, http://www.nanotechnology.hu/, Zs. Bálint, Hungarian Natural History Museum, Baross utca 13, H-1088 Budapest, Hungary
Resume : A photonic crystal (PhC), or a photonic band gap material (PBG) in general is a nanocomposite capable of manipulating light propagation. There are several cases of natural photonic nanoarchitectures in insects, generating specific coloration for camouflage and / or sexual communication . Many of the Lycaenid butterflies scales are colored by a PBG called pepper-pot structure . Recently we showed that the blue wing color of nine Polyommatine species, living in the same habitat, when measured with an optical spectrometer and analyzed with neural network software (NNS) is characteristic enough to allow species discrimination . In the present work we emphasize structure–color-species correlation. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used, as reported earlier  to fully characterize the 3D photonic nanoarchitecture. The same NNS was used successfully as in the case of color discrimination to discriminate species on the basis of the nanostructure of their scales. This could constitute an important step forward in elucidating the structure color relationship in nanostructure-based color engineering and also may give auxiliary information for the taxonomists.  L. P. Biró & J. P. Vigneron, Laser & Photonics Rev. 5(2011) 27 (DOI 10.1002/lpor.200900018)  L. P. Biró et al., Phys. Rev. E 67 (2003) 021907 (DOI:10.1103/PhysRevE.67.021907)  Piszter G et al.: Analytical Methods 3 (2010) 78 (DOI: 10.1039/c0ay00410c)  Kertész K. et al.: Physical Review E 74 (2) (2006), Art. No. 021922 (DOI: 10.1103/PhysRevE.74.021922)
|16:00||TRANSPARENT AND CONDUCTING SILVER NANOWIRE|
Authors : Şahin COŞKUN and Husnu Emrah UNALAN Department of Metallurgical and Materials Engineering, Middle East Technical University, 06531, Ankara, Turkey.
Resume : ABSTRACT Nanotubes and nanowires exhibit unique electrical, optical and catalytic properties. Discovery of their potential application areas depend only on their large scale synthesis and exploration of economic synthesis methods. Silver, as opposed to gold and copper, has higher electrical and thermal conductivity; thus it would be interesting to synthesize and explore nanoscale properties of silver nanowires. In this study, we have synthesized silver nanowires through a simple solution based polyol process. In this method, silver seeds are formed through the reduction of silver nitrate by ethylene glycol at 170 oC, which is followed by the continuous addition of silver nitrate to form nanowires under the presence of poly(vinyl pyrrolidone). Following purification process, nanowires are suspended in ethanol and spray coated onto glass and polyethylene terephthalate substrates. The electrical and optical properties of the silver nanowire thin films are then investigated. The thin films were found to be highly transparent and conducting with values comparable to indium tin oxide, giving %85 transparency at 550 nm. wavelength and 30 ohm/square sheet resistance. We will present a detailed analysis of the thin film properties according to nanowire density , nanowire length and controlled annealing . Keywords: Siver Nanowires, Thin films, Polyol Process.
|16:00||ZnO-containing nanotubes and core/shell nanowires from thermal oxidation of ZnTe and ZnTe/Zn nanowires|
Authors : K. Gas1, E. Janik1, W. Zaleszczyk1, I. Pasternak2, E. Dynowska1, K. Fronc1, S. Kret1, A. Kamińska4, J. F. Morhange3, M. Wiater1, R. Hołyst4, E. Kamińska2, T. Wojtowicz1, W. Szuszkiewicz1 1 Institute of Physics PAS, Al. Lotników 32/46, 02-668 Warsaw, Poland 2 Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warsaw, Poland 3 Institut des Nanosciences de Paris, UMR 7588, UMPC, 140 rue de Lourmel, 75015 Paris, France 4 Institute of Physical Chemistry, PAS, ul. Kasprzaka 44/52, 01-224 Warsaw, Poland
Resume : One-dimensional (1D) semiconductor nanostructures like, e.g., nanowires (NWs) or nanobelts recently attracted a great deal of attention due to their potential application in electronic and optoelectronic nanodevices. Among many materials zinc oxide is particularly intensively researched due to its wide direct-gap (3.37 eV at 295 K) and a large exciton binding energy of 60 meV. In this paper we report on successful fabrication of 1D ZnO-containing structures basing on molecular beam epitaxy grown ZnTe NWs using gold-catalyzed vapor-liquid-solid method. Both “as-grown” ZnTe and ZnTe/Zn core/shell NWs on their original GaAs or Si substrates, as well as samples containing these NWs mechanically removed from the substrates and deposited onto Si wafers were oxidized either by annealing in air or in flowing O2 gas using the rapid thermal annealing process. Scanning and transmission electron microscopy revealed that depending on oxidation’s conditions either ZnTe/ZnO core/shell NWs or nanotubes containing ZnO are obtained. We assessed their chemical composition using energy dispersive X-ray spectroscopy. Complementary information about the structure properties was obtained by X-rays diffraction performed with the use of synchrotron radiation. The optical properties of nanostructures were also investigated by Raman scattering. The studies were partially supported by the European Union within European Regional Development Fund, through grant Innovative Economy (POIG.01.01.02-00-008/08).
|16:00||Spontaneous Formation of A Nanotube From A Square Ag Nanowire|
Authors : M. Konuk1, S. Durukanoğlu2 1 Department of Physics, Istanbul Technical University, 34469 Istanbul, Turkey 2 Faculty of Engineering and Natural Sciences, Sabancı University, 34956 Istanbul, Turkey
Resume : The recently observed phenomenon of spontaneous formation of a tube from a regular, square Ag nanowire , during the elongation of silver nano-contacts, has been investigated through molecular static and dynamic simulations based on the interaction potentials obtained from the embedded atom method. With molecular static calculations, we investigate the effect of strain on this particular type of transformation by focusing specifically on square Ag nanowires. With molecular static calculations, we investigate the effect of strain on this transformation by focusing specifically on square Ag nanowires. With molecular dynamic simulations, on the other hand, we discuss the effect of temperature on the structural evolutions of various lengths of silver nanowires as they are constantly exposed to strain. We further examine the relevance of the wire length to the formation of tube from the wire. Our results from both molecular static and dynamic simulations demonstrate that both the length of wire and the nature of applied stress – uniform or non-uniform, are important contender in formation of these hollow structures. Through first principle calculations based on the density functional theory, we will also discuss on the electronic nature of this specific type of transformation. This work is supported by TUBITAK under Grant No. 109T105.  Lagos M.J., Sato, F., Bettini, J., Rodrigues, V., Galvao, D.S., Ugarte, D., Nature Nanotechnology, 4, 149, (2009).
|16:00||Defects in silicon nanowires: an ab initio study|
Authors : G. Petretto (1,2), A. Debernardi (1) and M. Fanciulli (1,2) (1) Laboratorio MDM, IMM-CNR, Via C. Olivetti, 2, 20864 Agrate Brianza (MB), Italy (2) Dipartimento di Scienza dei Materiali, Università degli studi Milano-Bicocca, 20125 Milano, Italy
Resume : Silicon nanowires are promising candidates for future nanodevices and for quantum information applications. In light of these possible application we have performed ab initio simulations to obtain informations about the electronic properties when dimensions reduce to nanometric scale. In this work we have investigated the atomic and electronic structures of cylindrical, hydrogen passivated silicon nanowires with diameters ranging from about 0.8 to 2 nm, containing a single substitutive defect. Also, different defect position has been considered with respect to the section of the nanowire . Particular attention has been devoted to the hyperfine parameters of the defect. Our results agree with with the confinement model which predicts an increase in the bandgap and of the defect ionization energy at small diameters. We obtained that, from the calculation of the formation energy, the defect has a slightly higher probability to form near the surface of the nanowire. Concerning hyperfine parameters we observed that the contact term increases compared to the values in the bulk, as it is expected from the confinement of the wavefunction of the defect level. Moreover we verified that moving the defect towards the surface leads to strong reduction in the contact term. Our simulations are based on plane-wave supercell DFT and PBE exchange correlation functional. The spin properties have been computed with the aid of the projector augmented wavefunction method and MT pseudopotentials.
|16:00||Embedded Atom Method Potentials for Al, Ni, Co and Their Alloys|
Authors : Berk ONAT 1 , Sondan DURUKANOGLU 2 1 Informatics Institute, Istanbul Technical University, Turkey 2 Faculty of Engineering and Natural Sciences, Sabancı University, Turkey
Resume : We have developed semi-empirical many-body type model potentials for Al, Ni, and Co metals to investigate the static and dynamic properties of their binary and ternary intermetallic compounds. The formalism is based on the embedded atom method (EAM). The potentials describing pure elements are built through the fitting the structure constants and total energies to those respective experimental values obtained for fcc structure of Al and Ni, and hcp structure of Co. The potentials for binary Ni, Al, and Co and ternary Al-Co-Ni alloys, on the other hand, are constructed using the formalism developed by Voter et al. ,which involves not only the pure element potential transformations, but also fitting procedures for the associated alloy structures to correctly describe the pair part of the potential. Although the binary compounds of Ni-Al, Co-Al and Co-Ni are extensively studied, both experimentally and theoretically, with a particular focus on total energies and structure constants of their structural phases we are not aware of any experimental study on Co-Ni binary alloy systems with a specific focus on their structural properties. Thus, the reliable fitting values for cohesive energies, elastic constants for binary alloy structures of Co-Ni are obtained using the first principle total energy calculations, in the formalism of density functional theory (DFT). We specifically look at the phases of Al-Ni-Co ternary alloys with defects in bulk and nanostructures.
|16:00||Recombination dynamics of ZnO nanowires: Surfaces states versus mode quality factor|
Authors : M. R. Wagner1, J. S. Reparaz1, F. Güell2, G. Callsen1, R. Kirste1, J. R. Morante2,3, and A. Hoffmann3 1 Institute of solid state physics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany 2 Departament d’Electrònica, M-2E, IN2UB, Universitat de Barcelona, C/Martí i Franquès 1, 08028 Barcelona, Catalunya, Spain 3 Institut de Recerca en Energia de Catalunya (IREC), C/Josep Pla 2, 08019 Barcelona, Catalunya, Spain
Resume : The great diversity of recently produced wide band gap nanostructures such as nanodots, nanocrystals, tetrapods, nanorods, and nanowires have opened an entirely new field of research activities. In the case of ZnO, a giant exciton-polariton coupling has been theoretically suggested for quantum dots, and recently experimentally demonstrated for a single ZnO nanowire. The longitudinal-transverse exciton-polariton splitting LT was shown to be as high as 164 meV for ZnO nanowires, i.e., almost two orders of magnitude larger than in bulk samples. In this work, we investigate the optical properties of ZnO nanowires grown using the vapor-liquid-solid (VLS) technique using Au nanoparticles and Au thin films as catalysts. In particular, we focus on the influence of finite size on the recombinations dynamics of these wires. We demonstrate that the diameter as well as the length of the nanowires determines the lifetime of the neutral donor bound excitons. Our findings suggest that while the length is mainly responsible for different mode quality factors of the cavity-like nanowires, the diameter determines the influence of surface states as alternative recombinations channels for the optical modes trapped in the nanocavity. In addition, the comparison of nanowires grown using different catalysts shows that the surfaces states strongly depend on each precursor characteristics which might be of great importance for the optimization of future applications based on these nanostructures.
|16:00||Extended X-ray Absorption Fine Structure and Mössbauer study of iron oxide nanoclusters exhibiting giant exchange-bias|
Authors : J. Sanchez-Marcos(1), R. Martínez-Morillas(1), F. Jiménez-Villacorta(1,2), E. Céspedes(1), Nieves Menendez(3), C. Prieto(1) 1. Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 – Madrid, Spain 2.European Synchrotron Radiation Facility, SpLine Spanish CRG Beamline, BP 220-38043 Grenoble Cedex, France 3. Dep. Química-Física Aplicada, C-II, Universidad Autónoma de Madrid, Cantoblanco, 28049 – Madrid, Spain
Resume : Gas-phase aggregation technique has been used to prepare oxidized iron nanoclusters. Depending on the grown conditions, different exchange-bias field (up to outstanding values of 3250 Oe at low temperatures) has been obtained. This work reports on the understanding of exchange bias variation after taking into account cluster size characterization by atomic force microscopy as well as crystallographic phases present in nanoparticles made by X-ray absorption (X-ray Absorption Near Edge Structure and Extended X-ray Absorption Fine Structure) and Mössbauer and spectroscopies. Experimental results give essential information to be used in the interpretation of magnetic properties. Samples with the highest exchange-bias values are formed only by hematite phase (antiferromagnetic α-Fe2O3). This fact let to discard a metal/oxide core-shell arrangement, which is typically obtained with this gas-phase aggregation technique and which allows a ferromagnetic/antiferromagnetic nanostructure for a straightforward explanation of exchange-bias. Additionally, it is shown that slightly different conditions in the preparation method change the cluster size or the oxidation degree, which fully determines the variation of exchange-bias magnitude. Giant exchange-bias in single phase α-Fe2O3 samples is explained in terms of sub-stoichiometric α-Fe2O3 nanoclusters that softens the interaction between the two antiferromagnetic iron sublattices and allows an easy decoupling between them.
|16:00||Smart porous polymeric nanoparticles: morphological and thermal behaviour.|
Authors : N. Rescignano1, I. Armentano1, M. Amelia3, A Credi3, J. Kenny 1,2 1Materials Engineering Center, UdR INSTM, University of Perugia, Str. Pentima 4, 05100 Terni, Italy 2Institute of Polymer Science and Technology, CSIC, Juan de la Cierva 3, 28006 Madrid , Spain 3Department of Chemistry "G. Ciamician" University of Bologna, via Selmi 2 - 40126 Bologna, Italy
Resume : The aim of the present work was to design, develop and characterize smart nanosystems, based on biodegradable polymers, having well defined size. Poly(DL-lactide-co-glycolide), PLGA and Poly(L-lactide) (PLLA) nanoparticles (NPs) were prepared by double emulsion (water/oil/water) method with subsequent solvent evaporation. NPs were characterized in terms of morphology by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), and size distribution by dynamic light scattering (DLS), and thermally by differential scanning calorimeter (DSC). Finally, the in-vitro degradation study were performed in physiological conditions. Biodegradable NPs display a spherical surface structure with an homogeneous size distribution, and an average diameter of 180 nm for PLLA and 218 nm for the PLGA, as measured by DLS. The NP nanoporous structure was measured by a thermoporosimetry method, providing information about pore diameter and volume. In-vitro biodegradation study shows the gradual surface degradation of NPs and the effect of polymer properties on NP aggregation and degradation. Smart polymeric nanosystems may offer promise for revolutionary improvements in tissue engineering, diagnosis and targeted drug delivery systems. Smart materials are poised for take off and will certainly promise an exciting future at the interface of chemistry, biology and material science.
|16:00||Size Tuning at Full Yield in the Hot Injection Synthesis through a Facile Adjustment of the Nucleation Event|
Authors : Sofie Abé, Richard Karel Čapek, Bram de Geyter, Zeger Hens Physics and Chemistry of Nanostructures, Ghent University, Krijgslaan 281-S3, 9000 Ghent, Belgium
Resume : Colloidal semiconductor nanocrystals or quantum dots (QDs) attract extensive interest in nowadays science. For the characterization of their materials properties and their use in applications, the synthesis of QDs with sharp size distributions at a desired mean size is of fundamental importance. In widely used colloidal synthetic strategies based on hot injection, size control is achieved by adjusting the reaction time. Although highly successful, these procedures have an intrinsic drawback: sizes below the size reached at the end of the reaction driven growth regime (post-focused size) are only obtained at the expense of a reduced reaction yield. Here, we propose two strategies for controlling the post-focused size, either by adjusting the initial nucleation rate or the solubility of the reactive monomer. We first explore these concepts by means of a QD synthesis model that is based on the assumption that nucleation and growth of QDs involves a monomer species, formed at a specific rate from the initial precursors. Next, the modeling predictions are verified using a synthesis for CdSe QDs. This involves the confirmation of the basic model assumption, i.e., the formation of a monomer species, and the demonstration of size tuning at full yield from diameters of 2.8 to 4.1 nm. Our strategy thus makes it possible to prepare monodisperse batches of different sized QDs at high yield, which is a key result for synthesis reproducibility and efficient reaction upscaling.
|16:00||In-situ SEM micropillar compression - Room temperature ductile to brittle transition in InP|
Authors : R. Ghisleni and J. Michler Laboratory for Mechanics and Nanostructures, EMPA - Swiss Federal Laboratories for Materials Testing and Research, Feuerwerkerstrasse 39, CH-3602 Thun, Switzerland
Resume : Current fabrication technology is capable of producing micro- to nano-meter scale structures. The mechanical response of such structures has been shown to depend upon length scales such as pillar diameter. This finding contradicts the classical laws of mechanics which assume that mechanical properties are independent of sample size. This contradiction has fostered an increasing number of investigations into mechanical size effects. In an effort to characterize and understand the mechanical behaviour dependence on size, an investigation on single crystal indium phosphide (InP) semiconductor micropillars is presented. Single crystal InP micropillars were fabricated by focused ion beam (FIB) technique. The pillars diameter ranged from 500 to 10000 nm with a height to diameter aspect ratio of three. The micropillars’ mechanical responses were investigated by uniaxial compression tests performed inside a scanning electron microscope (SEM). The results show that InP materials exhibited a brittle to ductile transition with a decrease in pillar diameter. The deformation mechanism is associated to the formation of Shockley partial dislocations. The decrease of the projected pillar diameter on the crystal slip plane below the equilibrium distance between the leading and trailing partial dislocation is postulated to trigger the transition from a brittle to a ductile behaviour.
|16:00||The Interlayer Mass Transport in Double-Layer Island Decay on Ag(111)|
Authors : Berk ONAT 1 , Sondan DURUKANOGLU 2 1 Informatics Institute, Istanbul Technical University, Turkey 2 Faculty of Engineering and Natural Sciences, Sabancı University, Turkey
Resume : After the inspiring experimental studies of interlayer mass transport in the decay of islands and mounds on Cu(111) and on Ag(111), there has been a surge in determining the atomistic diffusion mechanisms leading to the fast decay of double-layer islands. We have therefore undertaken a molecular dynamic study of double-layer island decay on Ag(111), using a vastly tested, semi-empirical interaction potential based on the embedded atom method. Our simulations on various temperatures yield results that are consistent with the experimental finding that the decay rate changes dramatically each time the edge of the top layer touches the edge of the bottom layer. In order to determine the atomistic processes leading to a sudden increase in decay rate, we have developed a computer program that determines and counts the specific hopping and exchanges processes taking place during the run time. We find that the two-atom exchange mechanism on B type steps is the leading processes compared to the other possible mechanisms. Interestingly, the MD run at 650K reveals a significant increase in total number of two-atom exchange processes taking place over A type steps. This work has been supported by TUBITAK under Grant No. TBAG-106T567.  M. Giesen et al., Phys. Rev. Let. 80, 552 (1998).  K. Morgenstern et al., Phys. Rev. Lett. 82, 3101(1999).
|16:00||Structural and Polarized Raman studies in GaAs wires|
Authors : M. R. Correia a)*, A. Cros b), A. Cantarero b), N. C. Taborda c), M. V. B. Moreira c), J. C. González c) a) I3N-Universidade de Aveiro, Dept. Física, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal, b) Departamento de Física Aplicada y Electromagnetismo, Instituto de Ciencia de Materiales, Universidad de Valencia, Polígono La Coma s/n, 46980 Paterna, Spain c) Department of Physics, Federal University of Minas Gerais, Campus da Pampulha, Av. Antônio Carlos, 6627,31270-901 Belo Horizonte, MG Brazil
Resume : This study comprises two samples of GaAs nanowires grown by Molecular Beam Epitaxy on Si(111) semi-insulating substrates. The substrates were drop coated with colloidal gold nanoparticles dispersed in water and with 5 nm of diameter to be used as catalysts for the nanowires growth. The sample with higher doping level was grown at 500 C, while the sample with lower doping level was grown at 625 C. Both samples were grown in ultra high vacuum conditions and exposed to simultaneous fluxes of As, Ga and Mg during 120 minutes. The nominal doping levels of the samples were 1.31012 cm-3 and 1.2 1019 cm-3. Single GaAs wires, previously mechanically transferred onto a Si substrate, were optically characterized by polarized micro-Raman Spectroscopy using the 514.5 nm line of a Ar+ laser as excitation. The measurements were performed at room temperature in backscattering geometry, scanning each sample along the wire axis. The polarization of the scattered light was analyzed by measuring the components parallel and perpendicular to the wire axis. The Raman results are consistent with the presence of both wurtzite-rich and zinc blend-rich regions along the wires axis. The growth temperature dependence of the crystalline phase formed preferentially along the wire will be discussed.
|16:00||Hydrothermal Synthesis of Cubic Nanoassemblies Comprising Octahedral CeO2 Nanocrystals and Hexanedioic Acid|
Authors : Seiichi Takami, Shunsuke Asahina, Osamu Terasaki, and Tadafumi Adschiri
Resume : Recent progress in synthetic methods for inorganic nanoparticles has facilitated their application as components for miniaturized devices. One strategy to construct such devices involves the controlled preparation of two-dimensional or three-dimensional periodic assemblies of nanoparticles. We believe that non-spherical nanoparticles should realize various assemblies through anisotropic interparticle interactions. In this presentation, we report the synthesis of cubic nanoassemblies of octahedral CeO2 nanocrystals in the presence of hexanedioic acid (HOOC(CH2)4COOH). By using high-resolution TEM and EBSD analysis, we confirmed that the crystallographic orientation of the primary nanocrystals are almost the same among one nanoassemblies. Therefore, the assembly with keeping the each crystallographic orientation realized the controlled synthesis of cubic nanoassemblies.
|16:00||Iron oxide superparamagnetic nanoparticles synthesized by laser pyrolysis: the influence of O2 on the structural and magnetic properties|
Authors : F. Dumitrache, C. Fleaca, R. Alexandrescu, I. Morjan, I. Sandu, C. Luculescu, A. Barbut Laser Photochemistry Laboratory, National Institute for Lasers, Plasma and Radiation Physics (NILPRP), 402 Atomistilor Str., 077125, Magurele – Bucharest, Romania O. Marinica, C. Daia, L. Vekas Center of Fundamental and Advanced Technical Research, Romanian Academy – Timisoara Division, 24 Mihai Viteazu Bd., RO-300323, Timisoara, Romania V. Ciupina Ovidius University of Constanta, 124 Mamaia Bd., 900527, Constanta, Romania
Resume : Superparamagnetic nanosized iron oxide particles, with crystalline mono domains close to that of maghemite/magnetite were prepared by the laser pyrolysis of a reactive mixture containing vapors of iron pentacarbonyl (as iron source) carried by ethylene (as sensitizer) and a mixture of oxygen and argon (as oxidizing agent). Here we report the successful control of the saturation magnetization by the amount of oxygen in the oxidizing mixture. TEM and XRD analysis of the synthesized nanopowders demonstrate an improved crystallinity with increased oxygen percent in the reactive mixture. Much more, in spite of the relative constant mean particle diameter (about 4-5 nm), there is an increase of the mean crystallite sizes of maghemite/magnetite phase. Hysteresis loop measurements performed at room temperature confirm the superparamagnetic character of nanoparticles. At the same time, these measurements indicate a marked increase of the saturation magnetization i.e. from 3.9 emu/g to 44.5 emu/g, when the amount of oxygen in the mixture with argon increases from 20 % to 66 %, respectively. The ability to dispersion of the magnetic nano-material was tested by performing DLS measurements in aqueous and alcoholic solutions.
|16:00||Raman monitoring of stress effects in annealed single layer graphene|
Authors : P. Russo, G.Compagnini Dipartimento di Scienze Chimiche, Università di Catania
Resume : Graphene, a two dimensional building block for carbon allotropes of many other dimensionality, shows remarkable electronic and optical properties that attract enormous interest. Graphene’s unique properties make it a promising material for future electronic devices. In order to make graphene a real technology, a control of its electronic and mechanical properties is a must. In this respect, a crucial step for the use of graphene layers in device fabrication is the deposition onto suitable substrates, understanding the interaction with them. Till now, micromechanical cleavage of graphite has been used to produce high-quality graphene sheets. The aim of this work is to study the strain effects induced in graphene by annealing processes using Raman spectroscopy. Here, the graphene samples have been prepared by mechanical cleavage and transferred onto a Si wafer with a certain thickness of SiO2. After thermal treatments performed in vacuum at temperatures up to 400° C, the Raman spectra show significant changes in both the most prominent features of graphene (G and 2D bands). Moreover we observed a peculiar behaviour of the 2D band with increasing temperature, attributed to lattice distortion which could be induced by the interaction with the substrate.
|16:00||Synthesis and Characterization of Silver doped Zinc Oxide Nanowires by Hydrothermal Method|
Authors : Aysegul AFAL and Husnu Emrah UNALAN Department of Metallurgical and Materials Engineering, Middle East Technical University, Ankara (06531), Turkey.
Resume : Hydrothermal method for the synthesis of zinc oxide (ZnO) nanowires is highly appealing due to its easy procedure, simple equipment and low temperature. ZnO, in its natural state exhibits n-type conductivity. Addition of impurities often leads to remarkable changes in their electrical and optical properties, which suggests new applications. Among the many possible dopant species being studied for ZnO, silver (Ag) can be an attractive candidate as a p-type dopant revealed in thin film structures. In this work, we demonstrate the synthesis of silver doped ZnO nanowires via hydrothermal method. Both undoped and Ag-doped ZnO nanowires are grown inside an aqueous solution at 90°C over substrates coated with zinc oxide nanoparticles. Silver doping is achieved by simply adding Ag salt into the aqueous solution. We have analyzed the morphology and distribution of the nanowires with field-emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). Optical properties and the bandgaps of the nanowires have been investigated by UVVIS and photoluminescence spectroscopy. The structural and chemical properties have been characterized through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Keywords: ZnO Nanowires, Silver Doping, Hydrothermal Method
|16:00||Magnetic properties of industrially important low-doped Fe-Si-B rapidly quenched metallic alloys|
Authors : A. Nosenko, M. Zakharenko, V. Nosenko Department of Physics, Taras Shevchenko National University of Kyiv, 64, Volodymyrska st., 01601, Ukraine, firstname.lastname@example.org
Resume : Fe-Si-B-based rapidly quenched metallic alloys containing low amount of Ni, Co, Mo and Cr dopants are widely used in novel magnetic cores. The possibilities of improvement of the cores’ magnetic properties by doping and heat treatment are reported. Magnetic properties of Fe(Ni,Mo)80Si6B14 amorphous metal magnetic cores were determined for the as-cast material and after 30 min annealing at Ta=500 – 740K. Amorphous ribbons were prepared by rapid solidification of the melt. Dynamic re-magnetization loops were studied at B=0.2, 0.5, 0.8T and for the frequencies of 60, 400 and 1000Hz. It was found that increasing of Ta to a certain optimal value (for the basic alloy Fe80Si6B14 this Ta=650K) results in decreased dynamic coercive force Hc= 11.5A/m and core loss 4.3W/kg for re-magnetization frequency of 1kHz. At this temperature, the maximum initial magnetic permeability of 3600 at the frequency of 100kHz was observed. This is caused by the relaxation of the internal stresses. It was shown that the increase of Mo content in the alloy leads to a decrease of dynamic coercive force. For example, for Fe77Mo3Si6B14 alloy the following result was obtained: Hc= 6.2A/m and core loss 2.3W/kg at the frequency of 1kHz. Reasoning from the obtained magnetic properties the modified alloys are promising for the industrial use in ground leakage current sensors, current measuring transformers, pulse small-size transformers, filter chokes, reactors, storage transformers and induction magnetometers.
|16:00||Nanostructured thin porphyrin films for sensing applications|
Authors : M. Tonezzer1,2, G. Maggioni1, E. Dalcanale3 1Università di Trento, Dipartimento Ingegneria dei Materiali e delle Tecnologie Industriali, via Mesiano 77, 38123 Povo, Trento, Italy. 2 Laboratori Nazionali di Legnaro - Istituto Nazionale di Fisica Nucleare, Viale dell’Università 2, 35020 Legnaro (PD), Italy 3 D.C.O.I. – University of Parma and ISTM, UdR Parma, Viale delle Scienze 17/A, 43100 Parma, Italy
Resume : In the last years thin porphyrin films have gained increasing interest in vapour sensing field showing to be promising materials for selective VOCs detection, being usually deposited through chemical techniques. In this work an innovative plasma–based deposition technique, named Glow Discharge induced Sublimation (GDS), was employed for producing thin films of 5,10,15,20-meso-tetraphenyl cobalt porphyrin (CoTPP). GDS represents an extremely promising technique in sensor field allowing to produce nanostructured thin films characterized by high purities, rough morphologies and extremely high porosity. Purity is of paramount importance because residual solvent can partially hinder the film-analyte interactions, while film structures featuring rough surface and high porosity widely improve the film sensing capabilities. In this work the films have been studied through FT-IR, SEM and nitrogen physisorption measurements: the results showed that the GDS deposited films have purity, large surface roughness and extreme high specific surface area (181 m2/g). Optical sensing capabilities of the samples have been determined by exposing them to different concentrations of ethyl alcohol (EtOH): the measurements demonstrated the better sensing performances of GDS deposited films in terms of sensitivity, response times and recovery with respect to conventional chemical- and VE-deposited samples.
|16:00||Microstrain effects in nano-polycrystalline clusters|
Authors : A. Leonardi (1*), Mo Li (2), M. Leoni (1), P. Scardi (1) 1 University of Trento, Department of Material Engineering, Trento, Italy 2 Georgia Institute of Technology, Atlanta, USA * Contact author: e-mail: Alberto.Leonardi@ing.unitn.it
Resume : Atomistic simulation is an ideal tool to study the microstructure of polycrystalline materials at the nano- scale. As shown in this work, to be effective, suitable algorithms should be used for creating realistic microstructures. Further, we show how the contributions of atomic displacements (static and dynamic) and of microstrain (distortion at the grain boundaries) can be separated in a computer generated microstructure by combining the analysis of the local atomic arrangement with the corresponding simulated X-ray Diffraction (XRD) patterns. New insights can be obtained on the microstructure of nano-polycrystalline materials, and on the interpretation of the line broadening observed in the XRD patterns of real specimens.
|16:00||Spectroscopic Ellipsometry of plasmonic thin films and metamaterials|
Authors : T.W.H.Oates, Karsten Hinrichs - Leibniz – Institut für Analytische Wissenschaften - ISAS - e.V., Department Berlin, Albert-Einstein-Str. 9, 12489 Berlin, Germany; Milka Miric, Goran Isic, Borislav Vasic, Rados Gajic,- Institute of Physics, Belgrade University, Solid state Physics and New Materials, Pregrevica 118, 11080 Belgrade, Serbia; Raluca Penciu, Maria Kafesaki, Costas M. Soukoulis, Foundation for research and technology Hellas, Institute of Electronic Structure and Laser, P.O. Box 1385, 71110 Heraklion, Greece; Babak Dastmalchi, Michael Bergmair, Kurt Hingerl- Center for Surface and Nanoanalytics, Johannes Kepler University, Altenbergerstr. 69 4040 Linz, Austria Iris Bergmair- Functional Surfaces and Nanostructures, PROFACTOR GmbH, Im Stadtgut A2, 4407 Steyr-Gleink, Austria
Resume : Spectroscopy of nanostructures in the long wavelength limit (particle dimension << wavelength) provides a macroscopic view of the sample. However the inherent relationship between the nanostructure and plasmonic spectral features allows one to determine the size, shape and orientation of metallic nanoparticles from optical spectra. We demonstrate how fast non-destructive spectroscopic ellipsometry measurements of dipolar plasmon modes provide a powerful characterization method for silver and gold nanoparticle films at surfaces. Higher order resonances in metamaterials, both electric and magnetic in origin, also provide an insight into the nanoscale structure of these materials. We show how spectroscopic ellipsometry with the advantage of relative phase information is ideally suited to exploring these unique materials, and determine the effective permittivity and permeability of split ring resonators and fishnets from ellipsometric measurements. Relating these parameters to the nanostructure paves the way for non-destructive real-time monitoring of the self-organized growth of metallic metamaterials.
|16:00||Study of defects in gold nanowires using molecular dynamics simulations|
Authors : Ana Sofia A. Vila-Verde, Dr. Dorothy Duffy Department of Physics & Astronomy, University College London, London, UK and London Centre for Nanotechnology, University College London, London, UK
Resume : Gold nanowires and nanopillars are promising components for nanodevices, used for their good electrical properties and low reactivity with air, water and several chemicals. During device manufacture and usage, the nanowires might be subject to significant mechanical stresses. While material response to stress is well understood at macroscopic scales, this is not so at the nanoscale. In this work, we explore the effect of compression and expansion conditions on gold nanowires with the use of molecular dynamics simulations using classical, atomistic models. Nanowires with several cross-section areas are subjected to two independent tensile and compressive rates. Due to the different cross-sections, distinct deformations are visible at the surface of the nanowires. Our results suggest that the compression of the nanowires induces several dislocations that cross the width of the nanowire, leaving steps on the nanowire surface, but a defect-free interior. In contrast, a tensile load creates more dislocations in the interior of the nanowire.
|16:00||Investigation of the catalytic and sensor properties of the metallic clusters (Pd, Cu, W) embedded in the silicon porous layer|
Authors : T.I. Gorbanyuk, V.G. Litovchenko, V.S. Solntsev. V. Lashkaryov Institute of Semiconductor Physics of NAS Ukraine Prospect Nauki, 41, 03028 Kiev, Ukraine E-mail: email@example.com
Resume : In this work we present the results of the studies of charge transport in slightly thermo oxidized porous silicon (Sipor) in dependence of metal cluster Pd, Cu, W, Al distribution in porous silicon layer by means of I(V) and C(V) characteristics, secondary ion mass spectroscopy (SIMS) and Auger electron spectroscopy (AES). The morphology of Pd, Cu/Pd, WO3/Pd and silicon porous surface was characterised by SEM and AFM microscopies. Nanoporous silicon layers were prepared electrochemically on p-type B-doped (NA=41015 cm-3), (100)-oriented Si monocrystal using the solutions of HF (48%): C2H5OH. The alternative method of the porous silicon preparation was the plasmachemical treatment the single-crystal silicon surface in (SF6+O2=90%+10%) plasma. The ultrathin films of Pd, Cu, W, Al were deposited using the magnetron deposition technique and modified vacuum evaporation. Depending on the size of metal clusters the interaction of molecular hydrogen, hydrogen sulphide and water vapour with fresh and aged Pd/Sipor, Cu/Pd/Sipor, WO3/Pd/Sipor thin films has been studied. It was also found nanoporous silicon doped by Cu and/or W/WO3 give rise the enhanced adsorboelectric effects in the semiconductor-layered structures. In this case the using of thin catalytic composite metal/Sipor films with d- and sp- metals (Cu/Pd, W/Pd, Al) leads to the enhanced adsorption activity and stability to oxidation and ageing process. The physical mechanism has been proposed for explain the observed phenomena. A model based on the combination of hopping and tunneling mechanisms of charge transfer have been proposed.
|16:00||Optical and dielectric properties of TiO2 nanocrystals|
Authors : M.P.F. Graça*, C. Nico, M. Peres, M.A. Valente, T. Monteiro I3N- Physics Department, Aveiro University, Campus de Santiago 3810-193 Aveiro, Portugal
Resume : Titanium oxide nanocrystals synthesized by the Pechini method were calcinated at temperatures between 300 and 1000oC. The crystalline structure was analysed by X-ray diffraction, scanning electron microscopy (SEM) and Raman spectroscopy. A phase transition from the anatase to rutile crystalline phase was found to occur at temperatures near 500oC. The samples were characterized by photoluminescence (PL) and dielectric spectroscopy. The influence of the calcination temperature on the visible and near infrared luminescence is discussed. A correlation between the structural properties, luminescence and dielectric properties are discussed.
|16:00||Structural and optical properties modifications of ZnS nanopowders|
Authors : Rachida Saoudi, Myriam Moussaoui
Resume : Nanoparticles (NPs) have attracted very intense research due to the fact that their properties critically depend on the size of the particles. This holds especially for very small nanoparticles with diameters in the range of a few nm. The extremely small size of the NPs results in quantum confinement of the photogenerated electron-hole pair. When the radius of the particle approaches the Bohr radius of the exciton, the quantum size effect becomes apparent: the energy gap increases with decreasing the grain size, which leads to a blueshift of the optical absorption edge with respect to the bulk material. In order to exploit such size-tuneable properties, we synthesized ZnS nanopowders with size ranging from 2 to 100 nm by a simple, low-cost and mass production chemical method. The NPs were characterised by X-ray powder diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), UV–VIS absorption and photoluminescence spectroscopy. The photocatalytic activity of as-prepared ZnS nanopowders was also evaluated by using Rhodamine 6G and Methylene blue under UV irradiation, sun illumination and in dark. The obtained results demonstrate that these ZnS NPs are good candidate for photodegradation of organic pollutants.
|16:00||Carbon sealed monodispersed iron nanoparticles (< 10 nm) with low superparamagnetic blocking temperature (up to 25 K)|
Authors : Noemí Aguiló-Aguayo, Enric Bertran FEMAN Group, IN2UB, Dep. Física Aplicada i Òptica, Universitat de Barcelona
Resume : Carbon-encapsulated magnetic nanoparticles (CEMNPs) present a huge potential to be used in interesting applications related to biomedical field (in cancer therapy, as contrast agents in resonance imaging, as biosensors) [1-4], food industry , military defence , green chemistry  or data storage . However, controlling the size distribution of the magnetic cores is not an easy task . This poor control of size dispersion makes very difficult to characterize their magnetic properties and therefore, use them in the above applications. In addition, superparamagnetic behaviour is required in order to avoid a magnetic aggregation when the magnetic field is removed. To show this behaviour, nanoparticles have to present a diameter lower than a critical value, for example less than 10 nm in the case of iron nanoparticles . In this work, we present a systematic study of different superparamagnetic Fe@C nanoparticles obtained by using a modified arc plasma discharge (APD). Our technique allows us an accurate control of the diameter size of iron cores and thus, a detailed morphological (Raman spectroscopy, electron microscopy observations) and magnetic (blocking temperatures) characterization of the samples.  - Y. Xu et al, Nanotechnology 10 (2008) 1-4.  - R. Abu-Reziq et al, Journal of the American Chemical Society 128 (2006) 5379-82.  - E. S. Leite et al, Hyperfine Interact 195 (2010) 99-104.  - R. Fernández-Pachecho et al, Journal of Magnetism and Magnetic Materials 311 (2007) 318-22.  – A. Jasper et al, Environmental Engineering Sciences 27 (2010) 85-93.  - Liu B, Weller DK. US patent 7158346, 2007.  – F. Schüth et al., Angewandte Chemie International Ed 46 (2007) 1222-44.  - D. L. Leslie-Pelecky. Chem Matter 8 (1996) 1770-83.
|16:00||Effect of ZrO2 on the structural and dielectric properties of niobium oxide nano-powders.|
Authors : M.R.N. Soares1, C. Nico1, M. Matos2, R. Monteiro2, T. Monteiro1, L.C. Costa1, M.P.F. Graça1, M.A. Valente1 1 I3N- Physics Department, Aveiro University, Campus de Santiago 3810-193 Aveiro, Portugal 2 KEMET Electronics, Évora - Portugal
Resume : During the last two decades, niobia based materials have received much attention due to their properties and applications. It is known that Nb forms several stable oxide structures: NbO (electric conductor), NbO2 and Nb2O5 (dielectrics). The niobium pentoxide presents high potential for technological applications namely in electronic devices such as capacitors, optical waveguides, optical interference ﬁlters and due to its electrochromatic behavior it can be used in smart window applications. The effect of the dopping in order to stabilize the zirconia high-pressure orthorhombic phase at ambient conditions, was studied in several works. However, the influence of zirconia addition on the structural and dielectric properties of NbOx powders is a subject not very explored. In this work, pellets of the composite system (100-x)NbO.(x)ZrO2, with x = 1, 2 and 5 mole% were prepared sintered at temperatures between 300 and 1100oC. The XRD patterns showed that the increase of the sintering temperature promotes the structural transformation from cubic to orthorhombic (800 ºC) and to monoclinic (1100 ºC). Raman spectroscopy confirmed the crystalline structure. The samples were also characterized using optical absorption, Photoluminescence and impedance dielectric spectroscopy. The influence of the morphology (analysed by SEM), optical and structural characteristics on the dielectric properties, at room temperature and in the frequency range 40 Hz – 100 MHz is discussed and reported.
|16:00||Lateral continuity of ultrathin tungsten layers for X-ray mirrors|
Authors : Nikola Radic, Rudjer Boskovic Institute, Zagreb, Croatia, Kresimir Salamon, Institute of Physics, Zagreb, Croatia, Pavo Dubcek, Rudjer Boskovic Institute, Zagreb, Croatia, Goran Drazic, Jozef Stefan Institute, Ljubljana, Slovenia, Marko Jercinovic, Rudjer Boskovic Institute, Zagreb, Croatia, Sigrid Bernstorff, Sincrotrone Trieste, Basovizza, Italy
Resume : For obtaining a considerable reflectivity of hard X-rays by tungsten/carbon multilayers for angles of incidence >2° a bilayer period of less than 2.5 nm is required. A further decrease of the bilayer period is mostly limited by lateral discontinuity of the tungsten layer below its average thickness of about 1.0 nm. In this work we have examined the development of tungsten layer continuity, starting from separate W islands which by percolation process form a perforated layer upon thickening, and finally make a continuous layer. A series of W/C multilayered stacks, with different carbon layer thickness and tungsten layer thickness, have been prepared by sequential RF/DC magnetron sputtering. With a nominal 1 nm C/1 nm W bilayer, a reflectivity (for λ = 0,154 nm) of about 10-15% has been achieved at about 2°. In order to explore the threshold of continuous tungsten layer formation, its thickness has been varied by reasonable steps in the 0,2 - 1,2 nm range. Special samples with a single tungsten layer in a sandwich between carbon layers have been prepared for the detailed examination by TEM which provides a direct insight into the local W-layer morphology. The „global“ information on the lateral W-layer continuity has been retrieved from GISAXS measurements. XRR measurements have supplied additional information for the onset of W-layer discontinuity. The obtained results allow an estimation of the thickness at which a continuous tungsten layer is formed.
|16:00||Low temperature growth of carbon nanowalls and nanotube networks by plasma-enhanced chemical vapor deposition|
Authors : H. J. Boettcher, M. Hoeltig, N. Reim and A. Mews Department of Physical Chemistry, University of Hamburg, Germany
Resume : Due to their high surface-to-volume ratio carbon nanotubes (CNTs) and carbon nanowalls (CNWs) are promising candidates as building blocks for electrical applications such as organic hybrid solar cells. The carbon nanostructures are directly grown by chemical vapor deposition (CVD) on a transparent conductive substrate such as indium tin oxide (ITO) which requires careful tuning of reaction conditions, in particular reaction temperatures below 600 °C. Here we present two different pathways for the low-temperature synthesis of CNT networks and CNWs by template-assisted thermal CVD (TCVD) and plasma-enhanced CVD (PECVD), respectively. During thermal reaction of acetylene gas in a TCVD setup, the tube density can be controlled by means of an porous aluminum oxide template layer on top of the substrate. The average pore size and interpore distance and thus the CNT density can be tailored by the choice of the electrochemical etching parameters e.g. anodization time and applied voltage. In a second approach, a capacitively coupled plasma setup is employed to generate large areas (~ 4 cm²) of highly-uniform and transparent films of CNWs on ITO substrates. It will be shown that the substrates' surface roughness as well as the chosen plasma power greatly affects product morphology and film homogenity. While the PECVD reaction of acetylene gas on ITO at moderate plasma powers yields CNW films, the usage of glas or silicon wafers leads to the formation of CNTs.
|16:00||Stress evolution during deposition and annealing of Cu/Au, Cu/Ag and Au/Ag bilayers|
Authors : D. Chocyk, A. Proszynski, G. Gladyszewski Department of Applied Physics, Lublin University of Technology, ul. Nadbystrzycka 38, 20-618 Lublin, Poland
Resume : Miniaturization of electronic devices requires a reduction in the thickness of layers to several tens of nanometer. Advanced microelectronic technologies based on thin film systems. The strong interest in the mechanical behavior of such systems is caused by reliability problems in these applications. It is known, that metals with dimensions less then micrometer posses plastic deformation different then bulk. The purpose of this study is to investigate change of stress and structure during deposition and annealing of Cu/Ag and Au/Ag bilayers. The thin films were deposited by evaporation onto silicon substrates in room temperature in ultra high vacuum. The total force per unit width in system as a function of temperature was in-situ determined by the use of the substrate curvature measurement method. The annealing measurements were done during thermal cycles of heating and cooling from RT to 400oC with rate 10oC/min. We analyzed systems with total thickness in range from 10 nm to 20 nm. We observed that during deposition the general trend in F/w for bilayers is similar to that observed for continuous deposition at early stage of growth. We observe that the first cycle of annealing is different from second and third cycles. This suggested that during the first cycle of annealing, irreversible modifications occur in the systems. Change in the slope of the elastic part of stress curve during heating indicates a change in the coefficient of thermal expansion of metallic films. In this presentation, the stress dependences on temperature will be presented and discussed.
|16:00||New gold-containing bimetallic catalysts for PROX reaction.|
Authors : I.V. Kolesnik, K.S. Gordeeva, M.V. Berekchiyan, A.V. Garshev, D.I. Petukhov, A.A. Eliseev, A.V. Lukashin, Yu.D. Tretyakov. Moscow State University, Materials Science Dept., Leninskie Hills, 119991, Moscow, Russia.
Resume : Selective oxidation of CO in presence of hydrogen (PROX) is one of the key reactions for hydrogen energy applications. Gold nanoparticles deposited on oxides of transition or rare earth metals are the most promising catalytic systems for this reaction. The activity of these catalysts is determined by particle size of gold and metal-support interface structure. In our work we developed a method for the preparation of gold-containing catalysts on with enhanced activity and selectivity. Mesoporous titanium oxide was selected as a support for the catalysts due to high specific surface area (300 m2/g), narrow pore size distribution and nanocrystalline pore walls. Gold was deposited from [Au(NH3)3OH](NO3)2 aqueous solution. Using of chlorine-free precursor allowed us to deposit silver simultaneously with gold simply adding AgNO3 to the solution. The reduction of metals was performed in H2 stream. Also, Pd-Au and Cu-Au catalysts were synthesized by the same way. Catalytic properties of the samples were studied at 323 K in gas mixture which contained 1% O2, 1% CO, 75 % H2 with He balance. The catalyst which contained 0.6% of Au and 0.1% of Ag has shown high activity (2.5 mol*s-1*g-1.cat) and the highest selectivity (more than 90%). TEM study of the catalysts has shown that they contain small gold particles 2-3 nm in diameter. Thus, introduction of silver allows to enhance selectivity of gold-titania catalysts in PROX reaction.
|16:00||Advanced Electron Paramagnetic Resonance for thin-film solar cells|
Authors : Alexander Schnegg, Jan Behrends, Matthias Fehr, Klaus Lips, Bernd Rech Helmholtz-Zentrum Berlin für Materialien und Energie Institut für Silizium-Photovoltaik, Kekuléstr. 5, D-12489 Berlin, Germany Freie Universität Berlin Institut für Experimentalphysik Arnimallee 14, D-14195 Berlin, Germany
Resume : In order to achieve optimum photovoltaic (PV) performance, novel materials and devices have to be developed, which can only be realized with the aid of tailor made simulation and characterization tools. In PV materials, where paramagnetic states determine charge transport and loss mechanisms, a unique probe is provided by these unpaired electron spins. This renders Electron Paramagnetic Resonance (EPR) the method of choice to quantify the total number of defects and obtain nanoscopic insight into their structural properties. This is especially true for thin-film Si materials where defect states can drastically influence the solar conversion efficiency. In spite of the success of EPR spectroscopy in Si PV research, recent EPR studies were limited by insufficient resolution as well as detection sensitivity. This situation changed with the advent of advanced EPR, which, in many cases proved to be able to lift these restrictions. Advanced EPR methods generally include approaches where: the resonance condition is matched to resolve a specific spin interaction, transient processes on the ns to ms time scale are investigated and indirect detection techniques are employed to study spin dependent transport processes. With these methods at hand we recently managed to shed new light onto the structural properties of function-determining defects states in thin-film Si materials and study their impact on spin dependent transport processes in thin-film Si solar cells.
|16:00||MULTI-WALL CARBON NANOTUBE FABRICATED WITH MICROWAVES FROM IRON ACETATE.|
Authors : G. Ortega-Cervantez, J. J. Vivas-Castro, G. Rueda-Morales and J. Ortiz-López Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional Edificio 9, UPALM-Zacatenco, 07738 México D. F., México.
Resume : Multi-wall carbon nanotubes (MWNTs) were synthesized using a domestic microwave oven (power:1000 W, frequency: 2.54 GHz) ). Samples were prepared by irradiating with microwaves for 60 to 120 minutes a mixture 30 wt % of iron acetate (99.999% purity) and 70 wt% of graphite powder (99.99% purity) placed in a vacuum sealed quartz ampoule. Obtained MWNT form plate of 2 micrometer thick approximately and with diameters between 10 and 50 nm. Samples were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy.
|16:00||The changes in ferromagnetic coupling on iron oxide nanoparticles with Mössbauer spectroscopy|
Authors : Sung Wook Hyun, Chan Hyuk Rhee, Sam Jin Kim and Chul Sung Kim Department of Physics, Kookmin University, Seoul 136-702, Korea
Resume : The high temperature thermal decomposition method was used to synthesize iron oxide, Fe3O4, nanoparticles. The prepared nanoparticles were irradiated by proton beam with 0, 10 and 20 pC/µm2, in order to investigate the changes of magnetic properties. The Rietveld refinement method was used to analyze x-ray patterns. It shows that the crystal structure is cubic spinel with space group of Fd3m and the lattice constants decreased from 8.3908 to 8.3701 Å with increasing proton irradiation. Also, the saturation magnetization (MS) at room temperature was decreased from 57.2 to 53.7 emu/g with increasing proton irradiation. The Mössbauer spectrum at room temperature for non-irradiated nanoparticles shows the superparamagnetic behavior. However, The Mössbauer spectra for 10 and 20 pC/µm2 irradiated nanoparticles show 6 absorption lines of ferromagnetic behavior. It can be explained that the proton irradiation induces the changes of ferromagnetic coupling between Fe3+ and Fe2+ ions.
|16:00||Size dependent band gap energy in stannite nanocrystals|
Authors : Il Jin Park, Hyun Tae Cho, Chul Sung Kim* Department of Physics, Kookmin University, Jeongneung-dong, Seongbuk-gu, 136-702 Seoul, Korea
Resume : The stannite has attracted considerable attention for absorber layers in thin film solar cells. In this research, we are attention to the changes of band gap energy for the stannite nanocrystals. The stannite nanocrystals were synthesized by high-temperature arrested precipitation in the coordinating solvent, oleylamine (OLA). To investigate the effect of crystal size, the solution heated to different reaction temperatures of 230 °C, 280 °C, and 330 °C. These were designated as A, B, and C, respectively. From analysis of HR-TEM data, as increasing the reaction temperature the crystal shapes are changes from sphere to polygon shape and crystal sizes are increased from 10 nm to 200 nm. The absorption spectra of the stannite nanocrystals are measured using UV-vis absorbance spectroscopy. The band gap of the stannite nanocrystals is estimated to be 1.3 eV, 1.6 eV, and 1.7 eV for C, B, and A respectively, by extrapolating the linear region of a plot of the absorbance squared versus energy. In order to study the change of the detailed local structure on samples, Mössbauer spectroscopy has to be applied. There are exist poorly resolved quadrupole doublet with electric quadrupole shift values are 2.73, 2.80, 2.83 mm/s for A, B, and C respectively, correspond to Fe+3 atoms and well resolved quadrupole doublet with electric quadrupole shift values are 0.59, 0.53, 0.50 mm/s for A, B, and C respectively, correspond to Fe+2 atoms for all samples.
|16:00||Spectroscopic Studies of Fullerene Clusters in Polar Solvents|
Authors : M.Biliy, L.Bulavin, V.Gubanov, O.Kyzyma, A.Naumenko National Taras Shevchenko University of Kyiv, 60, Vololodymyrska Str., Kyiv, 01601, Ukraine
Resume : The study of the peculiarities of the interaction of C60 with the solvent in the solvent mixtures of different polarity by the methods of Raman scattering, optical absorption, fluorescence and small-angle neutron scattering were performed. Changing the polarity of the solvent was achieved by changing the composition of the mixture, which included as the basis solvent N-methyl-2-pyrrolidone (NMP) (ε = 32), and weakly polar and strong polar solvents: toluene (ε = 2.7) and water (ε = 78), respectively. Absorption spectra were obtained using Specord UV/Vis spectrophotometer. The spectra of fluorescence were detected on Varian Cary Eclipse Fluorescence Spectrophotometer. Raman spectra were obtained on an automated complex based spectrometer DFS-24 (LOMO). Liquid systems C60/NMP characterize by the formation of the clusters, which sizes increase during the time from the preparation of mixtures. The observed aggregation of the fullerene with time in the liquid system C60/NMP practically does not depend on the initial concentration of the fullerene. By small-angle neutron scattering revealed the reorganization (destruction) of clusters of fullerene when added to the liquid system C60/NMP both water and toluene. The results of experiments on the spectroscopy showed a sharp decrease in the density of absorption in the region of electronic transitions and a significant decrease in the fluorescence quantum yield of N-methyl-2-pyrrolidone when adding C60. These facts indicate the effective electron capture of solvent molecules by fullerenes.
|16:00||The behavior of paramagnetic centers and Si-O bond population of oxidized nano-porous silicon surface.|
Authors : Mircea Bercu University of Bucharest , Faculty of Physics Str.Atomistilor 405, Bucharest –Magurele, Romania, PO-Box MG-11, RO-77125 firstname.lastname@example.org
Resume : Novel technologies of efficient solar cells and high sensitive gas sensors based on porous silicon (PS) are encouraged mainly by the large specific Si surface. Low temperature oxidation of PS changes its properties being considered as the main limitation. Oxygen bonding to highly reactive surface it is a specific feature of PS to be understood and eventually controlled. The behavior of the paramagnetic centers induced by oxidation of hydrogenated and dehydrogenated porous silicon (PS) was investigated by means of X band EPR (Electron Paramagnetic Resonance) in relation with the oxide formation starting as surface suboxide up to SiO2 surface layer. Oxygen bonding on fresh PS was monitored by FT-IR spectroscopy being compared with the corresponding induced paramagnetic centers revealed by EPR. The temperature dependency of the ratio of Si-O to Si-H groups indicates that saturation is simultaneously with the maximum of Pb like centers population. Oxidation of dehydrogenated PS samples shows a more complex evolution of the paramagnetic centers produced after oxide bonding at temperature ranging from 400C up to 6000C. In the case of dehydrogenated PS the evolution of EPR spectra start from an almost isotropic resonance at g=2.005 followed by a continuous changing up to axial symmetry corresponding to Pb like centre (gII||=2.002 and g┴=2.008). The amount of the Pb like paramagnetic defect population as a result of the extra strain in oxidized PS structures has been determined.
|16:00||VIBRATIONNAL PROPERTIES OF Si-Ge/Si ISLANDS ((113) and (111) facets)|
Authors : Hassan KASSEM
Resume : Many recent works have been devoted to the study of the growth of Ge and Si-Ge alloys on (001)Si substrates. Two main reasons are the origin of this interest. The first is a technological interest and concerns the potentiality of this structure in microelectronic and optoelectronic devices. In particular the formation of regular Ge-Si islands embedded in Si matrices is a promising technique for the fabrication of quantum dots for optoelectronic applications. The second reason is the nature of this structure, which involves two elementary semiconductor materials with perfect covalent bonding, both having cubic diamond crystal structures. In this paper, we explore the effect of lattice mismatch (4%) on the static and vibrationnal properties of big size Ge islands having (113) and (111) facets on Si substrate. The simulation is done by minimizing elastic energy describe strain and stress and taking into account the intermixing between the two materials. Then we study vibrationnal properties of these systems as function of the interdiffusion.
|16:00||KINETIC MONTE CARLO SIMULATION OF SEMICONDUCTOR HETEROEPITAXY ON IMPERFECT SUBSTRATE|
Authors : Hassan KASSEM
Resume : Interdiffusion, formation of islands and dislocations constitutes a source of perturbation on electronic and/or optical properties of electronic devices. In the case of heteroepitaxial growth with large lattice mismatch, these phenomena allow a better relaxation of the deposited layers resulting defect densities in the films. In this study, we explore these phenomena of compounds as function experimental conditions (lattice mismatch, temperature, defects in the substrate like steps, ….). Our simulations are based on Monte Carlo algorithms organized around elementary atomic processes. Strain is introduced as elastic energy terms in the approximation of valence force fields. The stress is relaxed after each step of the simulation. We are interested by macroscopic properties like layer compositions as function of interface distance and the global strain after relaxation in the case of a substrate having defects (steps, mesa, …). We examine in details the morphology of the film as term of segregation of impurities, and we discuss the spatial fluctuations
|16:00||Thickness-dependent “transrotational” nanostructure formed in thin amorphous films upon crystallization|
Authors : V. Yu. Kolosov, Ural State University, Ekaterinburg, Russia
Resume : Unusual transrotational  microcrystals can be grown in different amorphous films: strong (up to ~ 300 degrees per micron) regular dislocation independent bending (transrotation) of the lattice round an axis (or axes) lying in the plane of a growing thin-film crystal is revealed. Here we present the influence of film thickness for chalcogen-based films prepared by vacuum condensation. The growth and structure of crystals is examined by means of TEM (primarily bend contour method). It makes possible to trace crystal growth in local areas in situ, during phase transition initiated by e-beam. Film thickness dependence of transrotation is studied for crystals of Se, Te, Sb2Se3, Sb2S3 grown usually in initially amorphous films, evaporated with strong thickness gradient (thickness is decreasing in the range 100 nm - 15 nm over the film length ~50 microns). Transrotation is strongly increasing, about 10 times, as the film gets thinner: i - crystallisation front is moving from the thicker part to the thinner part of the film, ii - the separate consequent crystals are grown by local heating (annealing) of the film by focused electron beam, iii - fine-grained crystallisation (Te) spontaneously take place in amorphous film (Cd-Te) soon after film deposition. These observations are somewhat expected result since the thinner is the film the stronger can be elastic bending accumulated by the growing crystal. . Kolosov V.Yu. and Tholen A.R. Acta Mater. v. 48, 1829 (2000).
|16:00||New grafted copolymeres synthesies based on polyfluorure of vinyliden ( P.V.D.F )|
Authors : A. LAKHZOUM1 ; A. SERDANI2; A. DJEBAILI1*; J.P CHOPART3 1 Laboratory of chemistry and environmental chemistry L.C.C.E - University of Batna- Algeria 2 Laboratory of Physical chemistry- University of Skikda-21000- Algeria 3 Laboratory of Dynamics & Interfaces – LACMDTI- University of Reims, France
Resume : We have developed the ozonisation technique because it is easy to build; it is reproducible and allows the access to many polymers. On the other hand, the products obtained are stable from the reactivity point of view and can be used for a long period after their preparation. We studied the polymerisation of different monomers enhanced by the ozonised PVDF. For a better understanding of this reaction the decay constant of hydroperoxids and peroxides was determined at different temperatures together with their half life time. On one hand, we showed that this reaction satisfies the rules of first order reactions and the values of constant Kd obtained are the same order of magnitude as those found for polyethylene PE and polychlorure vinyl PVC ozonised at the same temperature and that ozonised PVDF can be stored at room temperature for few days to be used later as precursor in a polymerisation reaction. Having established the nature of the precursors and their decomposition speed, we studied the graft of various monomers using the techniques in solid and in solution. From this study we deduce that solid graft technique, besides its easy way of making, leads to better efficiency rates of graft with relatively short time reaction in comparison with those carried out in solution. In addition, the solid reaction can be controlled following the variation of the resistive couple as a function of time. It is worth noticing that the particular behaviour of acrylic acid which, in opposite to other monomers, gives better results in solid reaction than in solution reaction Key Words: Copolymer - PVDF- monomer - Graft- Kinetics - Synthesis
|16:00||The comparative study of the ozonisation of different polymers|
Authors : Z. SKANDERI1; A. SERDANI3; A. DJEBAILI2* ; J.P. CHOPART4 1 Laboratoire d’Etude des Matériaux Polymères LEMP- University of Batna- Algeria. 2 Laboratoire de chimie et chimie de l’environnement–Université de Batna-05000- Algérie 3 Laboratoire de chimie Physique. Institut des Sciences Exactes. University of Skikda-21000- Algeria. 4 Laboratory of Mechanical Stress-Transfer Dynamics at Interfaces – LACMDTI URCA,BP 1039, 51687 University of Reims Cedex2, France
Resume : We have found only that the polymers with aliphatic and halogened structure resist, within acceptable limit, to the ozone and the following order by sensibility were established. SBS < Resin of hydrocarbure < S but Hydro .S < EPDM << PVC < PVDF. As far as the copolymer ethylene-chlorotriflurethylene (E.Co.CTFE) is concerned we can find its reactivity around that of polyethylene P.E and poly (vinyl chloride) PVC but its classification remains difficult to establish since this polymer cannot undergo dosage in contrast with PE and PVC. We notice that PVDF is a polymer that resist to ozone and can be activated only after extended exposure time to this gas, subsequently we have investigated in details chemical modification that happen to this polymer after ozonisation and we have tried to prepare grafted copolymers. Unfortunately very few studies have been dedicated to the action of ozone on this type of compound in comparison to the cases widely treated of polyethylene, polypropylene or even more poly (vinyl chloride). Key words: Synthesis- Ozonisation- Peroxide – EPDM - P.E - E co C.T.F.E.
|16:00||Unharmonicity of Vibrational Modes and Band Structure of the 1-st and 2-nd Order Raman Spectra of Single-wall Carbon Nanotubes|
Authors : A. Naumenko1, Ni.Korniyenko1, V. Bliznyuk2 1National Taras Shevchenko University of Kyiv, Ukraine 2 Materials Science and Engineering Department, College of Engineering & Applied Sciences, Western Michigan University, USA
Resume : Raman spectra (RS) of single-wall carbon nanotubes have been studied in both the field of fundamental vibrational D and G-bands and in the region of their overtones 2νD and 2νG. Spectra have been excited by radiation of Ar -laser with various wavelengths λL: 514.5, 488 and 476.5 nm. The band shapes of carbon nanotubes and disordered graphite materials have been compared. It is shown, that with increasing of exciting photons energy a maxima of G-band in nanotubes spectra shifts to the low-frequency region, and for graphite materials it shifts to high-frequency area. The fine structure (FS) of the fundamental bands and their overtones 2νG и 2νD considered simultaneously. We revealed more fine structure components of G-band (1516, 1534, 1551, 1569, 1592.5, 1605, 1615 и 1624 см-1 при 514.5 nm) that it was observed earlier. Influence of short-wave continuous laser radiation on structure and properties of nanotubes is revealed. It confirms by significant increasing of overtone intensities with growth of excited energy while intensity of G-band changes a little. The abnormal behavior of unharmonicity of vibrational bands of carbon nanotubes is revealed under change of frequency of stimulating radiation. Observed anomalies of unharmonicity may be explained by appreciable change of ground electron state as a result of excitation of phonons in resonant conditions.
|16:00||Energy gaps and band offset determination of AlzGa1-x-zInxAsySb1-y /GaSb interface|
Authors : A. Jdidi1*, S. Abdi-Ben Nassrallah1 N. Sfina1 and M. Saïd1 1Unité de Recherche de Physique des Solides, Département de Physique, Faculté des Sciences de Monastir, 5019 Monastir, Tunisia J.-L. Lazzari2 2Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), UPR-CNRS 3118 associée à Aix-Marseille Université, Case 913, Campus de Luminy, 13288 Marseille cedex 9, France
Resume : In the intend to realize devices with high quantum efficiency and multi spectral emission especially around 3 µm, quinternary AlGaInAsSb is introduced as a new barrier material for GaSb-based type I devices. For this wavelength range, it is known that this quinary enhances the valence band offsets compared to GaInAsSb/AlGaAsSb structures. In this work, we present theoretical investigations of band gaps and conduction and valence band offsets of AlzGa1-x-zInxAsySb1-y/ GaSb interface at various indium, arsenic and aluminum alloy compositions 0≤x,y,z≤1. Calculations are performed using the model-solid theory combined with the empirical pseudopotential method under the virtual crystal approximation that takes into account the effects of the compositional disorder. Our results could provide more diverse opportunities to obtain desired electronic properties; in particular, the information gathered by the present work may be useful for emission around 3µm.
|16:00||Synthesis and optical constants of the sulfosalt Sn2Sb2S5 thin films|
Authors : A.Gassoumi , M.Kanzari, B.Rezig
Resume : In this paper, we report the structural properties of Sn2Sb2S5 in a powder form and in a thin-film form. Sn2Sb2S5 thin films were prepared by a thermal vacuum evaporation technique onto a glass substrates kept at room temperature 50°C .The optical constants such as n and k were determined by Wemple and DiDomenico model for several samples of different temperature annealing, using spectrophotometric measurements of the transmittance and reflectance at normal incidence in the spectral range 300–1800 nm. EDAX was proved that the films are nearly stoichiometric.
|16:00||Optimizing Laser-Material-Ambient Interactions and Nanoparticle Formation and Evolution following Laser Ablation of Thin Metal Films|
Authors : Natalie Haustrup, Gerard M. O'Connor
Resume : Understanding the formation and evolution of nanoparticles generated during laser ablation is imperative in controlling the health risk associated with the ablated material, minimizing contamination and enhancing ablation rates. There is also a keen interest in exploring the competitive analysis of nanoparticle generation compared with current techniques. Laser-material-ambient interactions are, however, complex due to the dynamic nature of the ablation environment and consequently it is difficult to characterize the process of nanoparticle formation and evolution. Al, Ni and Au films with thicknesses 10, 25 and 75 nm were ablated by nano- and femtosecond laser pulses. Generated nanoparticles were collected and their height and diameter measured using AFM and SEM, respectively. The grain sizes of all films were measured and related to the nanoparticle size. Results also identified that the thickness of the metal film is highly influential on the size and distribution of nanoparticles e.g. mean radius for Al nanoparticles generated from 10, 25 and 75 nm thick films were 7.4, 14.3 and 17.7 nm, respectively. The role of the ambient was also probed using a heavy molecular-weight fluorine gas, resulting in less polydisperse, smaller nanoparticles. The poster will also present a real-time spectroscopy setup to monitor the nanoparticle evolution following a femtosecond laser pulse.
|16:00||Investigation of size and morphology on optical properties of ZnO|
Authors : S.H. Mousavi Physics Department, Shahrood University of Technology, Shahrood, Iran and Leibniz-Institut für Neue Materialien gGmbH, Saarbrücken, Germany H. Haratizadeh Physics Department, Shahrood University of Technology, Shahrood, Iran
Resume : Different ZnO nanostructures were synthesized by direct oxidation of zinc shots. Our study on the growth condition of these novel nanostructures shows that they are generated by a 1D and 2D structures which can be easily controlled by the growth temperature and oxygen gas amount. The morphology and optical properties of ZnO nanostructures prepared by chemical vapour deposition under different conditions were investigated. In this study, the effect of growth temperature and Oxygen: Argon ratios (as active and carrier gas respectively) on ZnO nanostructures have been investigated. 1D and 2D structures of ZnO have been obtained and their structural properties were investigated by XRD spectroscopy ant field emission electron microscope (FESEM). Also, the effect of morphology on photoluminescence properties of these structures is studied.
|16:00||On Monodisperse LiYF4 and LiYF4:Pr Nanoscale Particles|
Authors : Benjamin Herden, Thomas Jüstel Muenster University of Applied Sciences, Stegerwaldstrasse 39, D-48565 Steinfurt, Germany
Resume : During the last decades, a large variety of nanoscale materials have become an essential part of lighting, imaging, and sensing applications. Due to the strongly deviating physical properties of nanoscale materials from bulk materials a closer look into novel systems is always of considerable interest. In this study, the host lattice LiYF4 was investigated w.r.t. synthesis of nanoscale batches and optical properties. It can be easily doped by trivalent lanthanides (viz. Pr3+), which results in UV and VIS emitting luminescent materials. Such nanoscale LiYF4 powder might be a suitable precursor for the preparation of transparent ceramic laser materials. Synthesis of nanoscale particles was performed by different preparation methods. For comparison purposes, bulk material was prepared via solid state method using a homogeneous mixture of the corresponding fluorides, viz. high purity YF3, LiF, and PrF3. Nanoscale particles were prepared either by hydrolysis of LiPF6 and the subsequent precipitation of fluorides or by the so-called micro emulsion method using cetyltrimethylammonium bromide (CTAB) dissolved in n-octanol wherein precipitation of fluorides takes place within the micelles. Moreover, particle agglomeration as function of the calcination temperature was studied. All obtained LiYF4 and LiYF4:Pr batches were characterised by recording x-ray diffraction patterns, particle size distributions, SEM images, and optical spectroscopy.
|16:00||Using nanoparticles to produce iridescent metallic effects on ancient ceramic objects|
Authors : G. Padeletti Istituto per lo Studio dei Materiali Nanostrutturati - CNR, PO box 10, 00016 Monterotondo Staz. (Roma), Italy P. Fermo Dipartimento di Chimica Inorg. Metallorganica e Analitica,Università degli Studi di Milano, Via Venezian 21, 20133 Milano, Italy
Resume : Nanosized materials have been often used in the past by ancient potters to realize objects characterized by shining surfaces. One of the most outstanding examples is represented by luster pottery. Luster was one of the most sophisticated technique for the decoration of majolicas during the Renaissance period. It consists of a thin metallic film containing silver, copper and other substances, like iron oxide and cinnabar, applied in a reducing atmosphere on a previously glazed ceramic. In this way, beautiful iridescent reflections of different colours (in particular gold and ruby-red) are obtained. This technique, at first developed in Iraq, was introduced in Italy from Spain. In Italy the potters of the two centres of Gubbio and Deruta (central Italy) became so expert that nowadays modern artisans are not able to reproduce the wonderful effects obtained during Renaissance. A complete characterization by means of numerous techniques (ICP-OES, ETAAS, XRD, SEM-EDX, TEM-EDX-SAED, SAXS and UV-Vis) investigating both elemental composition and surface optical properties, has been carried out an a great number of shards and precious work of arts stored in some important museums. This has allowed to draw some conclusions on the preparation technique partly disclosing the secrets of the past.
|16:00||Novel microwave microscope for measuring complex electromagnetic properties: the scanning microwave microscope|
Authors : H.P. Huber (1), M. Moertelmaier (2), C. Rankl (2), M. Hochleitner (1), M. Wallis (3), A. Imtiaz (3), Y.J. Oh (1), J. Smoliner (4), P. Hinterdorfer (1), H. Tanbakuchi (2), P. Kabos (3), F. Kienberger (2) (1) Institute for Biophysics, University of Linz, Altenbergerstrasse 69, , Austria (2) Agilent Technologies Inc. (3) National Institute for Standards and Technology, Electromagnetic Division, Boulder, USA (4) Technical University of Vienna, Institute for Solid State Electronics, 1040 Vienna, Austria
Resume : Scanning microwave microscopy (SMM) is a novel microscopy technology combining atomic force microscopy (AFM) with microwave network analysis. It allows to measure complex materials properties for nanoelectronics, materials science, and life science applications with operating frequencies ranging between 1 MHz and 20 GHz. Here we present the basic working principle of SMM and the first measurement of complex impedance at the nanoscale. Ultra-sensitive and calibrated measurements of nanoscale capacitances are shown with a noise level of ~2 aF (atto-Farad) useful for material science investigations . Calibrated dopant profiles are measured from 1014 atoms/cm3 to 1020 atoms/cm3 for nano-electronics characterization . High frequency electromagnetic properties of nanodots and fixed cells were investigated through local measurements with the SMM [3,4].  Huber et al, Rev. Sci. Instrum. 81, 113701 (2010)  Smoliner et al, J. Appl. Phys. 108, 064315 (2010)  Oh et al, Ultramicroscopy, accepted  Humer et al, J. Appl. Phys., accepted
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