bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of New Materials in A Four-Sample Thermoelectric Measurement System
Authors: Ghelani Nishant A. , Loo Sim Y. , Chung Duck-Young , Sportouch Sandrine , Nardi Stephan de , Kanatzidis Mercouri G. , Hogan Timothy P. , Nolas George S. 
Published: June 2019

ABSTRACTSeveral new materials in the CsBi4Te6, A2Bi8Se13, (A = K, Rb, Cs), HoNiSb, Ba/Ge/B (B = In, Sn), and AgPbBiQ3 (Q = S, Se, Te) systems have shown promising characteristics for thermoelectric applications. New synthesis techniques are able to produce samples at much higher rates than previously possible. This has led to a persistent challenge in thermoelectric materials research of rapid and comprehensive characterization of samples. This paper presents a description of a new 4-sample transport measurement system and the related measurement techniques. Special features of the system include fully computer-controlled operation (implemented in LabView™) for simultaneous measurement of electrical conductivity, thermo-electric power, and thermal conductivity. This system has been successfully used to characterize several new thermoelectric materials (including some of the above-mentioned compounds) and reference materials exhibiting a wide range of thermal conductivities.
The Dynamics of Avalanching Bead Chains
Authors: Bretz Michael , Rojo Alberto G. 
Published: June 2019

ABSTRACTAvalanching studies were performed on 2D beds of a unique granular material - uniform length, 2.06 mm diameter flexible metal bead chain. The dynamical behavior of the slowly rotating vertical chain beds was separately characterized using chain lengths of 1, 2, 5, 9 and 13 beads, respectively. Digital images were acquired at 30-second intervals and analyzed to provide comparisons of mean profiles, slope angle variations, avalanche mass distributions and surface step discontinuities. This study is designed to probe how elongation, flexing and rolling affect avalanching through interlocking and polymer-like behavior.
Ultrasound propagation in disordered granular media
Authors: Jia Xiaoping 
Published: June 2019

ABSTRACTWe have identified, according to the ratio of the wavelength to the grain size, two distinct types of pulsed ultrasound transmission through a dry bead packing under stress: one corresponds to coherent ballistic waves characterized by the effective medium description, the other to the waves scattered by the inhomogeneous stress field within the granular medium. Over long distances of transport, the multiply scattered waves exhibit a diffusive character. Also we investigate the dynamics of the granular medium during a compaction under cyclic loading-unloading. Both the macroscopic deformation and the microscopic rearrangement have been measured, via an ultrasonic correlation technique using the multiple acoustic scattering very sensitive to the change of the system configuration. It is found that as the packing fraction increases, there is a continuous evolution of the system in response to external loading, from an irreversible behavior towards more elastic one.
Analysis of shear bands in slow granular flows using a frictional Cosserat model
Authors: Nott Prabhu R. , Kesava Rao K. , Srinivasa Mohan L. 
Published: June 2019

ABSTRACTThe slow flow of granular materials is often marked by the existence of narrow shear layers, adjacent to large regions that suffer little or no deformation. This behaviour, in the regime where shear stress is generated primarily by the frictional interactions between grains, has so far eluded theoretical description. In this paper, we present a rigid-plastic frictional Cosserat model that captures thin shear layers by incorporating a microscopic length scale. We treat the granular medium as a Cosserat continuum, which allows the existence of localised couple stresses and, therefore, the possibility of an asymmetric stress tensor. In addition, the local rotation is an independent field variable and is not necessarily equal to the vorticity. The angular momentum balance, which is implicitly satisfied for a classical continuum, must now be solved in conjunction with the linear momentum balances. We extend the critical state model, used in soil plasticity, for a Cosserat continuum and obtain predictions for flow in plane and cylindrical Couette devices. The velocity profile predicted by our model is in qualitative agreement with available experimental data. In addition, our model can predict scaling laws for the shear layer thickness as a function of the Couette gap, which must be verified in future experiments. Most significantly, our model can determine the velocity field in viscometric flows, which classical plasticity-based model cannot.
Wavelength Selection in a Vibrated Granular Layer
Authors: Clément Eric , Labous Laurent 
Published: June 2019

ABSTRACTWe present a numerical study of a surface instability occurring in a bidimensional vibrated granular layer. The driving mechanism for the formation of stationary waves is closely followed. Two regimes of wavelength selection are identified : a dispersive regime and a saturation regime. For the saturation regime, a connection is established between the pattern formation and an intrinsic instability occurring spontaneously in dissipative gases. We also address the importance of the detailed dissipation laws determining the wavelength values.
Theory of Stress Distribution in Granular Materials: the Memory Formalism
Authors: Kenkre V. M. 
Published: June 2019

ABSTRACTA theoretical approach to the description of stress distribution in granular compacts is presented on the basis of a memory function formalism. Experiments which have motivated the approach are mentioned. The formalism is shown to provide an explanation of observed features of stress distribution in compacts, and to lead to existing theories in extreme limits, thereb y providing a unification of the theories. The memory functions are shown to be intimately related to characteristic spatial correlations in the granular system and are discussed on the basis of stochastic considerations.
A New Simple Non Linear Modelling of the Quasi Statics of Granular Media: predictions, comparisons with experiments
Authors: Evesque Pierre 
Published: June 2019

ABSTRACTFirst, a non linear incremental modelling is proposed to describe rheological behaviour of granular material under different simple (i.e. triaxial-, oedometric-, undrained-) stress-strain paths. Validity of isotropic-response assumption is demonstrated whatever the stress ratio as far as deformation range remains small (ε1<5%). This contradicts some recent hypothesis made on the evolution of contact distribution during anisotropic loading.
FACET: a two Dimensional Simulator of Polycrystalline thin film Growth
Authors: Zhang Jie , Adams James B. 
Published: June 2019

AbstractWe present FACET: a two dimensional simulator to model polycrystalline thin film growth, which links atomic scale processes to macroscopic phenomena. The model is based on the concept of describing the crystal surface in terms of preferred facets. Line segments were used to depict the profile of the grain and grain boundaries. Multiple nuclei are semi-randomly distributed along the textured or non-textured surface, and crystallographycally appropriate facets are created in the nucleation simulation. We use a Kinetic Lattice Monte Carlo (KLMC) method to calculate the inter-facet diffusion rates and use a continuum approach to grow the facets, hence the multiple grains. The software is Windows(95/98/2000/NT) based and has an integrated Graphical User Interface, within which a user can input deposition conditions and experimental and simulation data, visualize the nucleation and growth of the grains, and obtain the final grain structure and texture.
Calculation of Intrinsic Stresses and Elastic Moduli in Nonhomogeneous Thin Films
Authors: Andia Pedro C. , Costanzo Francesco , Gray Gary L. , Yurick Thomas J. 
Published: June 2019

AbstractAn approach is presented for the determination of the residual stresses and elastic moduli of particle systems resulting from computer simulations of particle or atomic deposition. The proposed technique is based on fundamental concepts of elasticity and is capable of capturing the variation of stresses and moduli as functions of position within the system. Application to a simple particle system consisting of a deposited thin film is demonstrated.
A Method to Simulate the Interface-Diffusion in Solid-State Bonding-Processes Considering the Elastic Deformation
Authors: Ito Takehiko , Saito Shigeki , Takahashi Kunio , Onzawa Tadao 
Published: June 2019

AbstractWe propose a new method to simulate the interface diffusion in the solid-state bonding-process. This method is more significant under the condition of low pressure and low temperature. It is available for the bonding of two bodies which consist of the atoms of the same kind and have slight surface roughness. In a conventional method, the elastic deformation during the bonding process is considered. The interface diffusion is enhanced and the bonding time decreases when the external pressure changes at appropriate frequency. In order to clarify the enhancement effect of changing the pressure, we examine three cases, i.e., the 1st pressure type is constant pressure, the 2nd type is zero pressure, and the 3rd type is the on-off pressure. Our results suggest the on-off pressure decreases the required time for the perfect bonding if we choose on appropriate frequency.
Interactions between Edge Dislocations and Interstitial Clusters in Iron and Copper
Authors: Osetsky Yu.N. , Bacon D.J. , Serra A. , Singh B.N. 
Published: June 2019

AbstractDislocations decorated by both clusters of self-interstitial atoms (SIAs) and small dislocation loops, are one of the microstructure features which can play an important role in post-irradiated deformation processes. The interactions between dislocations and clusters are important and are usually treated within the framework of isotropic elasticity theory. However, it is still not clear whether or not these interactions, especially for small clusters at short distances, can be treated accurately by elasticity theory. Comparative studies by atomistic simulation and elasticity theory can clarify this. Here we present a simple example of such a study where interactions between a glissile SIA cluster and an edge dislocation are studied in bcc-Fe and fcc-Cu using both techniques. In Fe we have studied the interaction of a dislocation with Burgers vector b= 1/2<111> lying along <112> direction with a SIA cluster with the same b situated at different distances below the extra half-plane. In Cu, the dislocation and cluster had b = 1/2<110> and the dislocation line was along the <112> direction. Interactions with clusters of diameter about 1nm were simulated. Elastic calculations were made within the isotropic theory with parameters estimated from atomistic simulation. The results obtained by both techniques are discussed and some preliminary conclusions for different cases are drawn.
Unstable Motion of an Edge Dislocation in a Solute Atom Atmosphere Studied by Kinetic Monte Carlo Simulations
Authors: Gu X. M. , Sun Y. Q. 
Published: June 2019

AbstractThe discontinuous yielding of a model material, which contains an edge dislocation moving in the atmosphere of solute atoms, is studied by Kinetic Monte Carlo (KMC) simulations. The stress-strain curves for a constant strain rate were obtained at different temperatures. The dislocation moves discontinuously, producing three types of serrated yielding behavior at intermediate temperatures for different imposed strain rates. Positive dependence of flow stress on temperature and negative strain rate sensitivity were observed in the regime of discontinuous motion. The present model, though highly simplified and not taking into account the collective behaviors of dislocations in real materials, does exhibit some of the basic features observed in experiments.
A Theory for Multi Damage Evaluation of TiN Thin Film
Authors: Misawa Kazunori , Okabe Tomonaga , Yanaka Masaaki , Shimizu Masao , Takeda Nobuo 
Published: June 2019

AbstractThe present paper experimentally studies the cracking phenomena of a TiN thin film on a titanium alloy, and presents a new approach to predict the number of cracks under tensile load. An elastoplastic shear-lag model is developed to obtain the stress distribution caused by the film cracks, which is found to agree well with that calculated with FEM. The number of thin film cracks is predicted using a Monte Carlo simulation using the present approach, and favourably compared with the experimental results.
Modeling of the Heterogeneous Deformation of an Aggregate of Grains
Authors: Erieau Philippe P. , Hoc Thierry P. , Rey Colette C. 
Published: June 2019

AbstractMultiple layers of an Interstitial Free (IF) steel microstructure are polished and analyzed using EBSP and Orientation Imaging Microscopy (OIM) technique. This enables to build a 3D finite element mesh which represents the actual grains arrangement. Then a 30 % reduction plane strain compression is applied on this mesh in order to capture the heterogeneous deformation of the aggregate. After deformation, many grains show large orientation spreads, and thus do not follow a Taylor type assumption. This computation also shows that the stored energy distribution depends on the chosen definition.
Incorporation of Highly Concentrated Iron Impurities in InP by High Temperature Ion Implantation
Authors: Cesca T. , Gasparotto A. , Habra N. El , Coati A. , Fraboni B. , Priolo F. , Moreira E.C. , Ciatto G. , Bocchi C. 
Published: June 2019

AbstractIron was introduced in InP by ion implantation with the aim of obtaining a high concentration of substitutional, electrically active, deep level impurities. A substrate temperature higher than 200 °C was maintained during implantation in order to reduce damage accumulation and Fe defect reactions. The lattice position of the implanted Fe atoms and its modification during annealing treatments was studied by means of Proton Induced X-ray Emission (PIXE) in channeling conditions and correlated with the ion induced damage measured by different techniques. The results show that a high fraction of substitutional Fe atoms is present after the implantation. This fraction is progressively reduced during thermal treatments by increasing the annealing temperature, with the formation of inactive Fe aggregates, probably in the form of small Fe-P complexes.
Dose Rate and Temperature Dependence of Ion-Beam-Induced Defect Evolution in Si and SiC
Authors: Posselt M. , Bischoff L. , Teichert J. , Ster A. 
Published: June 2019

AbstractA focused ion beam system is applied to investigate the dose dependence of the shape of Ge channeling implantation profiles in Si and SiC at two very different dose rates (1011 and 1018 cm-2 s-1), and for implantation temperatures between room temperature and 580 °C. The competing influence of dose rate and temperature observed is explained in terms of intracascade defect relaxation. For the different implantation temperatures, the time scale for defect reduction is estimated. The results obtained for Si are compared with those for SiC.
Comparison of deep level spectra of MBE- and MOCVD-grown InGaAsN
Authors: Kaplar R. J. , Ringel S. A. , Kurtz Steven R. , Allerman A. A. , Klem J. F. 
Published: June 2019

AbstractDeep level transient spectroscopy (DLTS) studies of both p-type (uid) and n-type (Sidoped), lattice-matched, 1.05 eV bandgap InGaAsN grown by molecular-beam epitaxy (MBE) are reported, and the results are compared to previous measurements of similar materials grown by metal-organic chemical-vapor deposition (MOCVD). In MBE-grown p-type InGaAsN, two majority-carrier hole traps were observed: H3' (0.37 eV) and H4' (0.51 eV), and no evidence was found for the presence of minority-carrier electron traps. These two traps appear to be similar to two levels, H3 (0.48 eV) and H4 (0.5 eV), previously characterized in MOCVD-grown InGaAsN. In MBE-grown n-type InGaAsN, we observed a shallow distribution of electron levels, E1' (0 < EA < 0.35 eV), as well as a deep electron trap E4' (0.56 eV) and a deep hole trap H5' (0.71 eV). E1' appears to be coincident with a superposition of two levels observed in MOCVD-grown InGaAsN, a shallow distribution termed E1 (0 < EA < 0.20 eV) and a discrete (though broadened) level E3 (0.34 eV). Further, E4' appears to be similar in character to a level observed in MOCVD-grown material, E4 (0.82 eV), although a disparity in activation energy exists. This disparity may be due to a temperature-dependent capture cross-section for one or both levels, a possibility that is currently under investigation. In contrast, H5' appears to have no analogue in MOCVD-grown material and thus may be unique to the MBE growth technique.
Application Of Room-Temperature Photoluminescence For Characterizing Thermally Processed Cz Silicon Wafers
Authors: Kirscht F. , Orschel B. , Kim S. , Rouvimov S. , Snegirev B. , Fletcher M. , Shabani M. , Buczkowski A. 
Published: June 2019

AbstractPL studies of oxygen precipitation related defects, stress relaxation related defects and doping striations in various silicon materials are presented. The sample spectrum includes a variety of dopant species, and the dopant concentration range covers several 1014 cm-3 to several 1019 cm-3. Lightly doped, precipitation-annealed polished wafers were intentionally contaminated with Fe, Ni and Cu. Several types of epi wafers based on heavily doped substrates have been investigated after full device processing. PL intensity in the investigated doping concentration range is controlled by three basic recombination mechanisms: radiative recombination competing with multi phonon Shockley-Read-Hall (SRH) and Auger recombination. SRH recombination is the major competing mechanism at low dopant concentration, and Auger recombination becomes important at increasing doping levels. Even though not yet fully understood, the PL technique applied in this study has generated practically useful results.
Control of Valence States for Zno And Zns with a Wide-Band Gap by a Codoping Method
Authors: Yamamoto T. 
Published: June 2019

AbstractWe have investigated the electronic structures of p- or n-type doped ZnO and ZnS based on the basis of the analysis of the results obtained by ab initio electronic band structure calculations. We find the doping problems of the two materials. They at highly N-doping levels have the narrow impurity bands at the top of the valence band, where holes are very localized by repulsion effects. As a solution to the doping problems described above, we proposed a codoping method: The deliberate codoping of the donors with N acceptors is essential for the enhancement of N-acceptor incorporation and delocalization of the N-impurity states with the electrostatic energy gain in p-type highly doped ZnO and ZnS.
Organic-semiconductor-based all-solid-state photoelectro chemical cells
Authors: Hudej Robert , Pavlica Egon , Bratina Gvido , Lavrencic-Štangar Urška , Vuk Angela Šurca , Orel Boris 
Published: June 2019

Abstract3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) layers exhibit significant photoresponse. Despite of unfavorable electronic energy level alignment at the dye/PTCDA interface, photon-to-electron conversion efficiencies as high as 1% were observed.
Structural and Optical Characterization of CuxGaySe2Thin Films under Excitation with Above and Below Band Gap Laser Light
Authors: Xue C. , Papadimitriou D. , Raptis Y.S. , Riedle T. , Esser N. , Richter W. , Siebentritt S. , Nishiwaki S. , Albert J. , Lux-Steiner M.Ch. 
Published: June 2019

AbstractCuxGaySe2MOCVD and PVD grown films were structurally and optically characterized by Raman, Micro-Raman and photoluminescence spectroscopy. Defect related photoluminescence excitation with wavelengths varying across the material band gap reveals: a) in Cu-rich CuGaSe2films, three band edge splitting due to the spin-orbit interaction and the crystal field, and donor-acceptor pair recombination between a shallow donor and two different acceptor levels, and b) in Ga-rich CuGaSe2films, donor-acceptor pair transitions between quasi-continua of donor and acceptor levels related to potential fluctuations. Raman spectra of CuxGaySe2films, excited by laser light near and below the material band gap, show intense modes at 197cm-1, 187cm-1, and 277cm-1, which can be used as indicators of crystallinity and Ga-content of the films. Polarization- and angular- dependent micro-Raman spectra of MOCVD CuGaSe2indicate that CuxSey-crystallites, dispersed on the surface of Cu-rich films, are grown oriented with their c-axis perpendicular to the film surface.
Micro-Fabricated Thin-Film Fuel Cells for Portable Power Requirements
Authors: Jankowski Alan F. , Hayes Jeffrey P. , Graff R. Tim , Morse Jeffrey D. 
Published: June 2019

AbstractFuel cells have gained renewed interest for applications in portable power since the energy is stored in a separate reservoir of fuel rather than as an integral part of the power source, as is the case with batteries. While miniaturized fuel cells have been demonstrated for the low power regime (1-20 Watts), numerous issues still must be resolved prior to deployment for applications as a replacement for batteries. As traditional fuel cell designs are scaled down in both power output and physical footprint, several issues impact the operation, efficiency, and overall performance of the fuel cell system. These issues include fuel storage, fuel delivery, system startup, peak power requirements, cell stacking, and thermal management. The combination of thin-film deposition and micro-machining materials offers potential advantages with respect to stack size and weight, flow field and manifold structures, fuel storage, and thermal management. The micro-fabrication technologies that enable material and fuel flexibility through a modular fuel cell platform will be described along with experimental results from both solid oxide and proton exchange membrane, thin-film fuel cells.
Grain Size and Chemical Composition Effects on the Grain Boundary Resistance of Ceria
Authors: Zhou Xiao-Dong , Anderson Harlan U. , Huebner Wayne 
Published: June 2019

AbstractStudies related to the effects of grain size (30nm – 5.0μm) on the electrical conductivity of undoped CeO2 and Ce0.90Gd0.10O1.95 were performed. A series of impedance spectra as a function of temperature and grain size were analyzed. It was found that the ratio of the grain boundary resistance to the total resistance became lower with decreasing grain size, increasing temperature or increasing Gd content. For the case of Gd doped CeO2, the source of the grain boundary resistance may be due to the trapping of oxygen ions in the grain boundary area.
Single-Source Approach for The Growth of I-III-VI Thin Films
Authors: Afzaal Mohammad , Deivaraj Theivanayagam C. , O'Brien Paul , Park Jin-Ho , Vittal Jagadese J. 
Published: June 2019

AbstractThe ternary chalcopyrite semiconductors I-III-VI are currently used for photovoltaic solar cell applications. In this study, AgIn5S8 thin films were prepared from a series of single-source bimetalorganic precursors, e.g. [(PPh3)2AgIn(SC{O}R)4] (R = alkyl) by aerosol assisted chemical vapour deposition (AA-CVD). The compounds can be used as single-source precursors for the deposition of ternary compounds (I-III-VI) by one-pot reaction using CVD process and they are found to be air stable, which is favourable in comparison with metal alkyl compounds, which are found to be pyrophoroic. The optimum growth temperature for the preparation of these films on glass and Si(100) substrates, was found to be above 350°C in terms of crystallinity, although deposition occurred at low temperatures. The films have been investigated using XRD, SEM and EDS. SEM analysis shows that all films are microcrystalline but have different morphologies depending on the growth temperatures. XRD results show evidence of the crystalline nature of these films. The results of this comprehensive study are presented and discussed.