bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase Transition Behaviors of AgInSbTe-SiO2 Nanocomposite Thin Films for Phase-change Memory Applications
Authors: Huang Yu-Jen , Chung Tzu-Chin , Wang Chiung-Hsin , Hsieh Tsung-Eong 
Published: August 2010

AbstractPhase-change kinetics, structure evolution and feasibility to phase-change memory (PCM) of Ag2In7Sb64Te27 (AIST) and its nanocomposite comprised of 85 wt.% AIST and 15 wt.% SiO2 were presented. In-situ heating x-ray diffraction (XRD) indicated nanocomposite transforms from amorphous to HCP structure during heating and incorporation of SiO2 increases the recrystallization temperature (Tx) of samples (189°C for AIST and 223°C for nanocomposite). XRD and transmission electron microscopy (TEM) analyses both revealed the grain refinement in nanocomposite. Kissinger's analysis found the increase of activation energy (Ea) of phase transition in nanocomposite, denoting the SiO2 embedment restrains the grain growth of AIST during recrystallization. Johnson-Mehl-Avrami (JMA) theory revealed the decrease of Avrami exponent (n), indicating that the phase transition is prone to be heterogeneous since the dispersed SiO2 particles may provide additional nucleation sites.Static I–V measurement indicated that the switching threshold voltage (Vth) of nanocomposite device (1.65 V) is higher than that of the AIST device (1.10 V). Increase of dynamic resistance in nanocomposite device leads to the reduction of writing current. I–V analysis also confirmed the retardation of recrystallization in AIST due to the incorporation of SiO2 and the rise of Ea is able to enhance the thermal stability of amorphous state in PCM devices.
Activated Pulsed Metalorganic Chemical Vapor Deposition of Ge2Sb2Te5 Thin Films Using Alkyl Precursors
Authors: Reso Denis , Silinskas Mindaugas , Kalkofen Bodo , Lisker Marco , Burte Edmund P. 
Published: August 2010

AbstractGe-Sb-Te (GST) thin films were deposited by chemical vapor deposition (CVD) and hot-wire chemical vapor deposition (HW CVD). Several precursor sets (tetraethylgermanium - trimethylantimony - dimethyltellurium (TEGe-TMSb-DMTe), tetraisopropylgermanium - triisopropylantimony - di-tertiarybutyltellurium (TiPGe-TiPSb-DtBTe) and tetraallylgermanium - triisopropylantimony - diisopropyltellurium (TAGe-TiPSb-DiPTe)) were tested for CVD. For the TEGe-TMSb-DMTe precursor set tellurium and germanium could be detected in the films for all deposition temperatures investigated, while Sb was found only in the films deposited at elevated temperature higher than 550 °C. The deposition temperature could be reduced by using two other precursor sets (TiPGe-TiPSb-DtBTe and TAGe-TiPSb-DiPTe). The Ge content, however, could not be sufficiently increased to obtain stoichiometric Ge2Sb2Te5 films. Therefore, the hot wire or catalytic method was applied to improve the decomposition of the precursors. In this case, the desired composition (e.g. Ge2Sb2Te5) was obtained at each investigated temperature by adjusting dosing and deposition parameters. Additionally, film roughness (as low as 2 nm) and deposition rates could be optimized by adjusting deposition temperature and pressure.
Ab Initio Calculations of Crystalline and Amorphous In2Se3 Compounds for Chalcogenide Phase Change Memory
Authors: Chen Renyu , Dunham Scott T 
Published: August 2010

AbstractAb Initio calculations of various configurations of In2Se3 compounds are used to gain insight into the transition from crystalline to amorphous phase. The structures considered are based on wurzite structures with 1/3 of indium sites vacant as observed experimentally. From extensive calculations for possible vacancy configurations in In2Se3 compounds, predictions based on the local coordination of In/Se atoms are made for the energetically favorable vacancy ordering structures. Results indicate that in the most stable In vacancy configurations, Se atoms have coordination of either 2 or 3 (In atoms have coordination of 4). Other coordinations lead to significantly higher formation energies. Results from analyzing the total energy and electronic structure of a range of off-stoichiometry, including vacancies, interstitials and anti-site, configurations, suggest that the energetically most favorable way to form In-rich material is via incorporation of Se vacancies, while Se occupying a vacant site is the most favorable for formation of Se-rich phase. Based on these calculations, predictions are made on how stoichiometry deviations impact structural evolution during phase change.
Evidence for Magnetic Polarons in Hole-Doped Cobalt Perovskites
Authors: Podlesnyak Andrey , Furrer Albert , Straessle Thierry , Pomjakushina Ekaterina , Conder Kazimierz , Khomskii Daniel 
Published: August 2010

AbstractA substitution of La3+ by Sr2+ in LaCoO3 induces holes in the low-spin ground state of the Co ions, which behave like magnetic impurities with a very high spin value (13 μB per hole). In this work, using single-crystal neutron spectroscopy, we prove that the charges introduced by strontium doping do not remain localized at the cobalt sites. Instead, each hole not only creates Co4+ in low-spin state, but it also transforms the six nearest neighboring Co3+ ions to the intermediate-spin state thereby forming a magnetic seven-site (heptamer) polaron. Spin-state polarons behave like magnetic nanoparticles embedded in an insulating nonmagnetic matrix. Therefore, lightly doped La1-xSrxCoO3 is a natural analog to artificial structures composed of ferromagnetic particles in insulating matrices.
Silver/Gold Heterometallic Nanostructures and Their Surface Plasmon-related Behaviors
Authors: Song Hyunjoon 
Published: August 2010

AbstractA combination of silver and gold is demonstrated in nanoscale objects. Silver and gold have similar but distinct chemical and physical properties. We employed three main chemistry related to silver and gold – underpotential deposition, epitaxial growth, and Galvanic replacement. Selective underpotential deposition of silver guided the growth direction of gold and generated gold octahedrons, cuboctahedrons, cubes, and rods. Epitaxial growth of silver on gold decahedral seeds formed silver-gold-silver heterometallic nanorods and wires. Galvanic replacement of silver for gold yielded asymmetric single hollow and symmetric double hollow structures. All silver/gold nanostructures exhibited characteristic optical features in the UV-vis-NIR ranges. Such structural variation and corresponding optical properties are useful for diverse applications in electronics, photonics, biology, and catalysis.
High transversal relaxivities of silica coated multicore iron oxide nanoparticles suitable for magnetic resonance imaging
Authors: Roig Anna , Taboada Elena , Rodríguez Elisenda 
Published: August 2010

AbstractWe report on high transversal relaxivity values of composite iron oxide-silica nanoparticles. To obtain the material, pre-formed maghemite nanoparticles were coated with silica by sol-gel chemistry, using supercritical fluids as the reaction media. The composite particles were monodisperse and consisted of a core of several maghemite nanoparticles, surrounded by a thick silica shell. The high pressure and high temperature process did not affect the iron oxide particle size but induced an increase on their saturation magnetization values, possibly due to an improvement of the particle crystallinity. These iron oxide-based materials present very high transversal relaxivity values which can be correlated to the magnetic moment and to the silica shell width of the composite particles. Moreover, composite particles are not cytotoxic and they are dispersable in polar solvents.
Active Nanostructures at Interfaces for Photocatalytic Reactors and Low-power Consumption Sensors
Authors: Gole James L , Ozdemir Serdar , Prokes Sharka M , Dixon David M 
Published: August 2010

AbstractActive nanostructures which provide unique transformations are being introduced to phase matched porous silicon (PS) nano/micropores to form a platform for low power consumption highly selective sensors and microreactors. TiO2-xNx photocatalysts have been formed in seconds at room temperature at the nanoscale via the direct nitration of anatase TiO2 nanocolloids. Tunability throughout the visible depends upon the degree of agglomeration and the ability to seed these nanoparticles with metal ions. Co metal ion seeding leads to the efficient room temperature phase transformation, of anatase to rutile TiO2, where normally much higher temperatures are required. Seeding of a properly nitridated TiO2 nanocolloid with transition metal ions (Co, Ni) allows for the enhancement of the infrared spectra of the TiO2-xNx nitridated titania surface in excess of 10-fold, providing a means to analyze for minor contaminants and intermediates. Evidence for nitrogen fixation is found in Fe treated systems. The TiO2-xNx systems act as visible light absorbing photocatalyts. These photocatalysts and additional nanostructured metal oxides can be placed on the surface of PS-based sensor and microreactor configurations to greatly improve the interface response.
Optoelectronic and Interfacial Properties of CNT and ITO on Borosilicate Glass and PET Substrates with Nano- and Hetero-structural Aspects
Authors: Park Joung-Man , Wang Zuo-Jia , Kwon Dong-Jun , DeVries Lawrence K 
Published: August 2010

AbstractNano- and hetero-structures of carbon nanotube (CNT) and indium tin oxide (ITO) can control significantly piezoelectric and optoelectronic properties in Microelectromechanical Systems (MEMS) as sensing and actuators under cyclic loading. Optimized preparation conditions were obtained for multi-functional purpose of the specimens by obtaining the best dispersion and turbidity in the solution. Optical transmittance and electrical properties were investigated for CNT and ITO dipping and spraying coating on boro-silicate glass and polyethylene terephthalate (PET) substrates by electrical resistance measurement under cyclic loading and wettability test. Uniform dipping coating was performed using Wilhelmy plate method due to it simple and convenience. Specimen was applied with spraying coating additionally. The change in the electrical and optical properties of coated layer is mainly dependent upon the number of dip-coating, the concentration of CNT and ITO solutions, and the surface treatment condition. Electric properties of coating layers were measured using four-point probe method, and surface resistance was calculated using a dual configuration method. Optical transmittance of CNT and ITO coated PET film was also evaluated using UV spectrum. Surface energy and their hydrophilic and hydrophobic properties of CNT and ITO coated substrates were investigated by wettability test via static and dynamic contact angle measurements. As the elapsing time of cyclic loading passed, the stability of surface resistance and thus comparative interfacial adhesion between coated layer and substrates was evaluated to compare the thermodynamic work of adhesion, Wa. As dip-coating number increased, surface resistance of CNT coating decreased, whereas the transmittance decreased step-by-step due to the thicker CNT and ITO networking layer. Nano- and hetero-structural effects of CNT and ITO solution on the optical and electrical effects have been studied continuously.
WO3 Doping Effects on the Photoelectrocatalytic Activity of TiO2 Nanotube Film Prepared by an Anodization Process
Authors: Tsai Hei Lok , Leung Micheal K.H. , Li Gui Sheng , Leung Dennis C.Y. 
Published: August 2010

AbstractWO3 doped TiO2 nanotube(WO3-doped TNT) thin film was fabricated by anodizing the TiO2 nanotube (TNT) film in an NH4F electrolyte containing WO4- ions. The sample was characterized by Field Emission Scanning Electron Microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–Vis diffuse reflectance spectroscopy (DRS). The results show that WO3 was successfully doped into TiO2 nanotubes and the absorption edge of WO3 doped TNT appeared to be red shifted. The photoelectrocatalytic (PEC) activity of WO3 doped TNT electrode was evaluated through the PEC degradation of aqueous Acid Blue 80. The experimental results demonstrated that the PEC degradation rate of WO3 doped TNT is increased by 48% and by 167% over that of non-doped TNT under UVA light irradiation and visible-light irradiation, respectively, at an applied potential of 1.54V. The degradation rates of WO3 doped TNT under photocatalytic (PC), electrochemical (EC), and PEC processes were compared. The results reveal the synergetic effect of PC and EC processes.
Nanoporous Anodic Alumina as Template and Mask for Functional Nanostructures Fabrication
Authors: Hernández-Vélez Manuel , Sanz R , Manso Miguel , Sanchez O , de Melo O , Asenjo Agustina , Minguez-Bacho I. , Vázquez Manuel 
Published: August 2010

AbstractNanoporous Anodic Alumina Films (NAAF) have been used for growing a lot of nanostructure functional materials. Of particular interest is the NAAF conversion into membranes (NAAM) with different highly controlled pore diameter and distribution to be used as templates and masks to grow a wide variety of nanomaterials. This work constitutes an approach to a review of our latest results regarding the use of NAAF and NAAM as templates in which II-VI semiconductor, functional oxides, hard materials and magnetic nanowires have been grown. The growth techniques and methods used include Isothermal Close Space Sublimation (ICSS), Magnetron Sputtering, electroplating and sol-gel. Ion Beam Irradiation (IBI) combined with different NAAM as masks has been also used for Titania substrates functionalization.
Magnetism in Cylindrical NiFe Nanotubes
Authors: liew hwifen , Goolaup Sarjoosing , Wang Xinghua , Lew Wensiang 
Published: August 2010

AbstractWe report the fabrication of ferromagnetic NiFe nanotubes with a wall thickness of 80 nm by electrodeposition in nanoporous templates. The structure and wall thickness of the nanotubes are controlled by the thickness of the conductive layer at the back of the templates. The NiFe nanotubes have shown soft magnetic material properties with high magnetic saturation and low coercivity. The NiFe nanotube arrays are preferentially magnetized in the perpendicular direction to the nanotubes. Micromagnetic simulation results show that a curling mode is perceived with the formation of opposite magnetic vortex states on the end of the nanotube surface during the magnetization process.
Material Properties in Codimension > 0: Graphene Edge Properties
Authors: Branicio Paulo Sergio , Srolovitz David J 
Published: August 2010

AbstractWhen materials are very thin in one or more dimensions, their equilibrium shapes are often curved/bent. Such shapes commonly represent a compromise between elastic strain energy and other thermodynamic forces (e.g. related to surface stresses, electrostatic interactions, or adsorption). Examples include ZnO and SnO2nanobelts, silica/carbonate helicoids, and graphene sheets and nanoribbons. Here, we demonstrate that when the equilibrium shape of a nanomaterial is not flat/straight, important fundamental material properties may be orders of magnitude different from their bulk counterparts. We focus here primarily on the graphene edges. Graphene in three dimensions is a codimensionc= 1 material; the codimension isc = D – d= 3 – 2 = 1, whereDis the dimensionality of the space in which the material is embedded anddis the dimensionality of the object. By contrast, a flat graphene sheet hasc= 2 – 2 = 0. We use the REBO-II interatomic potential to calculate the edge orientation dependence of the edge energy and edge stresses of graphene withc= 0 andc= 1. The edge stress for all edge orientations is compressive withc= 0. Both edge energy and stresses are in reasonable agreement with DFT calculations. The compressive edge stresses inc= 0 lead to edge buckling (out-of-the-plane of the graphene sheet) for all edge orientations (c= 1). The edge buckling inc= 1 reduces all edge energies and dramatically reduces all edge stresses to near zero (more than an order of magnitude drop). We also report the effect of codimension on the free energy and entropy of a graphene sheet and the elastic properties of ZnO nanohelices.
Simulations of Pressurized Water Flow through Carbon Nanotubes
Authors: Shaw Samantha , Faux David 
Published: August 2010

AbstractMolecular dynamics simulations of the flow of pressurised water through carbon nanotubes of chirality (9,0), (12,0), (15,0) and (18,0) have been undertaken at 298K with a water density of approximately 1240kg/m3. Results show that the rate of filling is least in the smallest diameter nanotube, but that there is less variation in the time taken to reach maximum occupancy. The water molecules are found to undergo restructuring due to their confinement, with detailed molecular arrangement dependent on CNT diameter. Enhanced rates of flow are shown for the (15,0) nanotube, highlighting the effect of nanotube diameter on confinement and thus on flow.
Electrical Properties of Pd-contacted Single-walled Carbon Nanotubes: A Scanning Probe Microscopy Study
Authors: Kononenko Oleg , Bozhko S I , Matveev V N , Volkov V T , Knyazev M A , Il'in A I , Matveev D V , Kasumov Yu A , Khodos I I 
Published: August 2010

AbstractPd is widely used in producing electrodes to single-walled carbon nanotubes (SWNT). However up to now its ability to form ohmic contacts to SWNTs was not employed in scanning probe microscopy (SPM). Here we present a study of SWNTs with Pd electrodes by SPM using Pd-coated tips. SWNTs were selectively grown on oxidized silicon substrates by low pressure CVD method. Pd electrodes were prepared to SWNTs to fabricate two terminal structures for SWNTs resistance measurements. It is shown that SPM Kelvin mode is a reliable technique for SWNT detection on insulating substrate. Contact potential difference between Pd electrode and SWNT is measured using the Kelvin mode.
Layer-by-layer CdTe Nanoparticle Absorbers for ZnO Nanorod Solar Cells - The Influence of Annealing on Cell Performance
Authors: Briscoe Joe , Gallardo Diego E. , Dunn Steve 
Published: August 2010

AbstractThe conformal coating of ZnO nanorods with CdTe nanoparticles using layer-by-layer (LbL) processing produces a quantum dot-sensitised solar cell. As the number of CdTe layers increases the absorption of incident light increases below the absorption onset of the nanoparticles (650 nm). Photoluminescence investigations of the CdTe-ZnO composite structure suggest a transfer of photoexcited electrons from the CdTe nanoparticles the ZnO nanorods. Filling of the semiconductor composite structure with CuSCN provides the solar cell with a p-type semiconductor to collect the photogenerated holes from the system. Annealing the CdTe-polymer coated nanorods lowers the series resistance of the cell by removing the polymer component of the film. A cell annealed at 350 °C has aJscof 0.12 mAcm-2, and aVocof 49 mV under 0.25 mW/cm2illumination.
Photovoltaic Devices from Silicon Nanoparticles
Authors: Rier Christoph , Schierning Gabi , Wiggers Hartmut , Schmechel Roland , Jäger Dieter 
Published: August 2010

AbstractIn this paper, results of designing, fabricating and characterizing photovoltaic devices made from tailored silicon nanoparticles are shown as proof-of-principle to adopt this material into the photovoltaic sector. The silicon nanoparticles are used as active material for direct separation of the light induced charge carriers. Homo pn-junctions were constructed by silicon wafers and silicon nanocrystals, the latter doped with the opposite carrier type than the wafers. Nanocrystals were sintered on top of the wafer by a spark plasma sintering process, maintaining the nanocrystalline character. This way, the nanoparticle layers are a combined absorbing and charge separating medium. Electrical characterization measurements of the devices show a reproducible short-circuit current of up to 20 μA under illumination. A maximum short-circuit current density of 6.25 μA/cm2 was realized.
Electronic Structure of La(Fe0.88Si0.12)13
Authors: Kamakura Nozomu , Okane Tetsuo , Takeda Yukiharu , Fujimori Shin-ichi , Saitoh Yuji , Yamagami Hiroshi , Fujimori Atsushi , Fujita Asaya , Fujieda Shun , Fukamichi Kazuaki 
Published: August 2010

AbstractLa(Fe0.88Si0.12)13 shows peculiar magnetic properties such as the first order paramagnetic-ferromagnetic transition and magnetic-field induced metamagnetic transition accompanied by the lattice expansion. The practical application using the magnetic transition temperature controlled by hydrogen absorption is expected in this compound. Here, the electronic structure of La(Fe0.88Si0.12)13 has been investigated by photoemission spectroscopy using synchrotron soft x-rays. The Fe 3s core-level photoemission spectra below and above the Curie temperature TC exhibit a satellite structure at ~ 4.3 eV higher binding energy than the main peak, which is attributed to the exchange splitting due to the local moment of Fe. The exchange splitting of the Fe 3s photoemission spectrum with the asymmetric line shape shows that the magnetization of La(Fe0.88Si0.12)13 is derived by the exchange split Fe 3d bands like the itinerant ferromagnetism in Fe metal, while the magnetic transition of La(Fe0.88Si0.12)13 is the first order. The valence band photoemission spectrum shows temperature dependence across the TC. The temperature dependence of the photoemission spectra is discussed based on the difference between the electronic structure in the ferromagnetic phase and that in the paramagnetic phase.
Kinetic Monte Carlo Simulation of the Aging of Nanoporous Metals
Authors: Wagner Gregory J. , Seif Dariush , Ong Markus D. 
Published: August 2010

AbstractA kinetic Monte Carlo (kMC) model for the simulation of the coarsening of nanoporous metals is developed and demonstrated. The model treats surface evolution through the mechanism of surface diffusion by following atoms hopping between sites on an FCC lattice. Using a generic model for event energy barriers, we are able to demonstrate trends in the simulation and show that at high temperatures, coarsening follows approximately the scaling law predicted by continuum surface diffusion theory; the behavior is less clear at low temperatures. By selecting event energies to model palladium we show that we are able to reach temperatures and time scales that have relevance to experiments and applications.
Atom Probe Tomography characterization of the microstructural evolution of a low copper reactor pressure vessel steel under neutron irradiation
Authors: Huang Hefei , Radiguet Bertrand , Todeschini Patrick , Chas Guillaume , Pareige Philippe 
Published: August 2010

AbstractA low copper reactor pressure vessel steel was characterised by atom probe tomography after neutron irradiation at different fluences. The specimens were irradiated within the frame of the Surveillance Program of a production reactor. Roughly spherical clusters enriched in nickel, manganese, silicon and, in a lesser extent, phosphorus and copper were observed at all fluences. The chemical composition of these clusters shows no evolution with fluence, as well as their diameter, close to 3 nm. Their number density increases linearly with the neutron fluence. A continuous segregation of the elements found in the clusters is also observed along dislocation lines, with similar enrichments.