bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dislocation Core Structure Evolution During Dislocation Glide in FCC Lattices
Authors: Soare M.A. , Picu R.C. 
Published: June 2019

AbstractA dislocation core model is developed in terms of a singular decomposition of the elastic field surrounding the defect in a power series of 1/rn. The decomposition is a Laurent expansion beginning with the term corresponding to the Volterra dislocation and continuing with a series of dipoles and multipoles. The analysis is performed for an edge dislocation in an fcc lattice. The field surrounding the dislocation is derived by means of atomistic simulations. The coefficients of the series expansion are determined from the elastic field using path independent integrals. When loaded by a shear stress smaller than the Peierls stress, the core distorts. The distortion up to the instability (Peierls stress) is monitored based on the variation of these coefficients. The stacking fault separating the two partials is characterized, by using a similar procedure, as a source of elastic field.
Dislocation and Grain Derived Theory for Kinematic Metrics of Finite Deformation to Replace Existing Elastic-Plastic Phenomenological Metrics
Authors: Stout Ray B. 
Published: June 2019

AbstractMost existing continuum kinematic metrics used for correlating experimental data sets from finite deformation tests are traceable to a two reference state configuration analysis proposed primarily by Lee[1]; namely, a deformed elastic-plastic back to an idealized zero stress plastic state. These analyses admit that material discontinuities would exist in arriving at a virtual state of zero residual stress, however, the elastic-plastic deformation process is considered a mathematically continuous spatial function process. Hence, atomic length scale metrics are not analytically introduced because of the continuity requirements of the embedded deformation function space. This is not a valid physical description given that the microscopic dislocation mechanism for the non-recoverable kinematics of crystal material deformations creates discontinuities between atomic planes of grains in a material sample. In addition, the mathematical structure of current continuum kinematic metrics is deterministic. This is also not physically realistic in describing materials' responses that are dependent on intrinsic metallic grain characteristics. This follows since an ensemble of material specimens have a randomness for the physical numbers per unit material volume per unit species volume for both dislocation density and grain lattice structure density function characteristics. These random functions are best described as classical probability density functions in a spatial, time, and species variable domain. A stochastic description for dislocation density in solids has been developed, and explicitly introduced in a finite deformational functional[2]. This finite deformational functional will be extended to include an explicit dependence on a stochastic grain lattice structure density function. Finally, analyses of this dislocation-grain deformational functional provide stochastic kinematic metrics for void or microcrack-type opening deformations at grain boundaries that contain length scale measures based on the physical attributes of both dislocations and grains.
X-ray Microbeam Investigation of Deformation Microstructure in Microindented Cu
Authors: Yang Wenge , Larson B. C. , Pharr G. M. , Ice G. E. , Tischler J. Z. , Budai J. D. , Liu Wenjun 
Published: June 2019

AbstractThe deformation microstructure under spherical microindents in single crystal Cu has been investigated with submicron spatial resolution using x-ray structural microscopy. A polychromatic, submicron diameter (∼ 0.5 μm) microbeam was used in combination with micronresolution depth profiling to make direct, nondestructive measurements of plastic deformation induced lattice rotations under an indent made with a 69 μm radius spherical indenter and 200 mN maximum load. Lattice orientations relative to the undeformed crystal were determined as a function of position under the indent using differential-aperture x-ray structural microscopy (DAXM). Rotation-axes and misorientation-angles were determined for micron steps along selected microbeam penetration directions.
Mesostructure of Textured Metal Materials: Experimental Study and New-Discovered Regularities
Authors: Perlovich Yuriy , Isaenkova Margarita , Fesenko Vladimir 
Published: June 2019

AbstractThe substructure inhomogeneity of real textured metal materials was studied by use of recently developed methods of X-ray diffractometry and data treatment. Main regularities of substructure inhomogeneity were revealed for the first time by the analysis of generalized pole figures. The structure of deformed metal includes an extremely wide spectrum of substructure conditions. The crystallographic orientation of grains is the most effective criterion for systematization of substructure inhomogeneities in textured materials. The dispersity of grains and the distortion of their crystalline lattice are minimal in texture maxima and increase up to highest values by passing to texture minima. The distribution of lattice elastic deformation in rolled metals most often shows a cross-wise pattern, consisting in alternation of quadrants with predominance of elastic extension or elastic compression.
Using Fluctuations To Locate The Surface Roughening Transition
Authors: Bentz Daniel N. , Jackson Kenneth A. 
Published: June 2019

AbstractAn analysis of the fluctuations of a {100} FCC interface has been used to locate the surface roughening transition in kinetic Monte Carlo simulations. These simulations were conducted using a spin 1/2 Ising model treatment of the solid-liquid interface. A temperature gradient was imposed on the simulation cell providing a restoring force to the interface. Fluctuations in the number of solid atoms in the system were measured using time correlations. The fluctuation dissipation theorem was employed to relate the characteristic times retrieved from the time correlation to the kinetic coefficients of the system. A dramatic change was found in these characteristic times, which locates the surface roughening transition.
Structural Studies of Copper Sulfide Film Growth: Influence of Humidity
Authors: Campin M. J. , Zhu J. G. , Sullivan J. P. , Barbour J. C. , Braithwaite J. W. , Provencio P. P. 
Published: June 2019

AbstractCopper is a critical material in electrical components and is subject to atmospheric sulfidation. This study characterized the product formed when Cu is exposed to a dilute (50-200ppb) H2S atmosphere at low (0.5%) to high (80%) relative humidity (RH). An important observation was that the Cu2S growth rate for long times is significantly higher for sulfides formed at low RH compared to high RH. In addition, it was found that for both low and high RH sulfidation, copper reacts to form the low chalcocite phase (Cu2S) as identified by x-ray and electron diffraction. Cross-section and plan-view TEM revealed that the Cu2S grains formed at high RH are 20-50 nm in size with a large amount of porosity, whereas the grains formed at low RH are 75-150+ nm and appear to undergo grain growth with little porosity as the film thickens.
Correlation between the Susceptibility to Breakdown and Surface Properties of Thin Films on Titanium Alloys in Physiological Fluids
Authors: Lopez Agustin Santana , Mirza-Rosca Julia , Popa Mihai V. , Demetrescu Ioana , Vasilescu Ecaterina , Drob Paula , Vasilescu Cora , Ionita Daniela 
Published: June 2019

AbstractCorrelation between the susceptibility to breakdown and surface properties of thin films on implant titanium alloys Ti-5Al-4V and Ti-6Al-4Fe in Ringer 1 and Ringer 2 solutions of different pH values (6.98, 4.35, 2.5) which simulate the conditions that can appear at the longterm (13,000 hours) contact between implant and tissues were studied in this paper. The passive films are very stable up to +1.8 V; Ti-6Al-4Fe alloy presents pitting attack at a pitting initiation potential of +3.5 V in Ringer 1 solution and at +3.9 V in Ringer 2 solution. The pitting protection potential is about +1.75 V in both solutions; this is a very noble potential. Impedance spectra were modeled with one time constant equivalent electrical circuit, typically for a compact oxide film, for all materials, in all tested solutions. The fitting parameters indicate a long-term stability.
Spatial separation mechanism in Si quantum dots deposited by chemical vapour deposition on SiO2
Authors: Puglisi Rosaria A. , Nicotra Giuseppe , Lombardo Salvatore , Spinella Corrado , Gerardi Cosimo 
Published: June 2019

ABSTRACTA systematic study on the Si inter-dot distance after nucleation on silicon oxide substrates is presented. The process has been followed from the very early stages of the dot formation up to 25% of coverages. Structural characterization has been performed by means of energy filtered transmission electron microscopy, which allowed us to observe dot sizes down to 0.5 nm in radius. Silicon nanodots are shown to be surrounded by a depleted zone, where no new Si dots are observed to nucleate. The average size of such a zone ranges between 4 and 9 nm, depending on the deposition conditions. The dot radius is shown to be proportional to the depleted region size, thus indicating the scaling behaviour of the process.
Semiconducting Aluminum Transition-Metal Quasicrystals
Authors: Krajčí Marian , Hafner Jürgen 
Published: June 2019

ABSTRACTWe report on a class of icosahedral aluminum-transition-metal (Al-TM) alloys with a true semiconducting behavior. The existence of a semiconducting gap is found to depend critically on a particular kind of Al-TM ordering defined by a simple rule in a 6-dimensional superspace. Any deviation from this 6D order leads to the formation of strongly localized defect states in the gap. The structure of the semiconducting quasicrystals belongs to the face-center-icosahedral structural class, the same to which also icosahedral AlPdRe belongs. The description of the structure is based on a modified Katz-Gratias-Boudard model. We have calculated the electronic structure for series of quasicrystalline approximants. In the density of states of the 1/1 approximant with 128 atoms/unit cell relaxed with Hellmann-Feynman forces we have found a real gap at or close to the Fermi level. To get a semiconductor the critical band-filling is 648 electrons per cell. It can be achieved for several different stoichiometries. We investigated semiconducting 1/1 approximants with various combinations of 3d, 4d and 5d transition-metals. The gap widens as a 3d or 4d metal is replaced by a 5d metal. Calculations for the 2/1 approximant with 544 atoms/cell show the persistence of the gap. The chemical composition for which semiconducting behavior is achieved varies in the sequence of the approximants, but the existence of the gap in the electronic spectrum persists in higher order approximants, provided the Al-TM ordering is respected. Icosahedral AlPdRe represents the quasiperiodic limit in this hierarchyof approximants. As substitutional defects which obviously exist in real samples of any quasicrystal lead to formation of localized states, a real sample of icosahedral AlPdRe seems to be a semiconductor with a band-gap filled by localized states.
The Effect of Strain Rate on the Yield Behavior of Iron-Based Lro Alloys at Elevated Temperatures
Authors: Lin H. T. , Wilcox R. C. , Chin B. A. 
Published: June 2019

AbstractThe sensitivity of iron-based LRO alloys to strain rate at elevated temperatures was investigated. The tensile results indicate that the iron-based LRO alloys exhibit a positive temperature dependence of yield behavior, but are insensitive to variations in strain rate between 10-5and 100sec-1. These observations, along with SEM and TEM results, suggest that previous proposed diffusion-controlled mechanisms are not responsible for the increase in yield strength with increasing temperature.
‘Seed Layers’ for the Preparation of Hydrogenated Microcrystalline Silicon with Defined Structural Properties on Glass
Authors: Ross Christoph , Mai Yaohua , Carius Reinhard , Finger Friedhelm 
Published: June 2019

AbstractMicrocrystalline silicon with properties relevant to highly efficient solar cells can be suc-cessfully prepared on glass for material characterization if a thin intrinsic ‘seed layer’ coating of the substrate is used. This is demonstrated by a detailed structure analysis on the base of Raman spectroscopy and photothermal deflection spectroscopy. The coating turns out to be crucial (1) for achieving a crystalline content as high as that of solar cell absorber material, (2) for creating a homogeneous structure in growth direction, and (3) for extending the range of deposition pa-rameters which lead to films with high crystallinity towards the regime of amorphous growth. Regarding electrical transport, ‘seed layer’ assisted growth results in a structure dependence of the dark conductivity which is very similar to that of material grown on bare glass. Regarding optical absorption spectra, residual interference fringes, which indicate structure non-uniformities, are clearly suppressed by means of ‘seed layers’. It is concluded that appropriate ‘seed layers’ play an important role for a comprehensive characterization and development of microcrystalline silicon layers for thin film devices.
The Nature of Native and Light Induced Defect States in i-layers of High Quality a-Si:H Solar Cells Derived from Dark Forward-Bias Current-Voltage Characteristics
Authors: Deng J. , Albert M. L. , Pearce J. M. , Collins R. W. , Wronski C. R. 
Published: June 2019

AbstractResults are presented on the defect state distributions in intrinsic a-Si:H layers with and without hydrogen dilution in p-i-n solar cells obtained directly from the analysis of dark forwardbias current-voltage (JD-V) characteristics. It is shown that there are distinct differences in the distributions of both native and light induced defect states between the two types of i-layers. Computer simulations using these distributions are presented which show excellent agreement with the experimental results not only for the JD-V but more importantly for the bias dependent differential diode quality factor n(V) characteristics. Results are also presented on the nature of the gap states and their evolution with light induced degradation as well as their effects on the performance and stability of high quality a-Si:H solar cells.
Radiation hard amorphous silicon particle sensors
Authors: Wyrsch N. , Miazza C. , Dunand S. , Ballif C. , Shah A. , Despeisse M. , Moraes D. , Jarron P. 
Published: June 2019

AbstractRadiation tests of 32 μm thick hydrogenated amorphous silicon n-i-p diodes have been performed using a high energy 24 GeV proton beam up to fluences in excess of 1016 protons/cm2. The results are compared to irradiation of similar 1 μm and 32 μm thick n-i-p diodes using a proton beam of 280 keV at a fluence of 3x1013 protons/cm2. Even though both types of irradiation cause a significant drop in photoconductivity of thin or thick diodes, all samples survived the experiment and recover almost fully after a subsequent thermal annealing.
High Electron Mobility (˜150 cm2/Vs) PECVD Nanocrystalline Silicon Top-Gate TFTs at 260 °C
Authors: Lee Czang-Ho , Sazonov Andrei , Nathan Arokia 
Published: June 2019

AbstractUndoped nanocrystalline silicon (nc-Si:H) films were prepared by conventional 13.56 MHz plasma enhanced chemical vapor deposition (PECVD) at 260 °C, using highly H2-diluted SiH4 plasma. The nc-Si:H films were evaluated using electrical, structural, and chemical measurements. The optimized nc-Si:H film showed an oxygen concentration (CO) of ˜1.5 X 1017 at./cm3 and a dark conductivity (σD) of ˜10-6 S/cm, while the Raman crystalline volume fraction (XC) was ˜85 %. Top-gate staggered TFTs with a ˜100 nm nc-Si:H channel layer and an amorphous silicon oxide (a-SiOx) as the gate dielectric were fabricated. The TFTs showed a field effect mobility (μFE) of ˜150 cm2/Vs, a threshold voltage (VT) of ˜2 V, a subthreshold slope (S) of ˜0.25 V/dec, and an ON/OFF current ratio more than 106. To the best of our knowledge, the TFT mobility reported here is the highest achieved to date using state-of-the-art nc-Si:H films prepared by direct PECVD.
Stark Splitting in Photoluminescence Spectra of Er in a-Si:H
Authors: Kumeda Minoru , Takahashi Mitsuo , Morimoto Akiharu , Shimizu Tatsuo 
Published: June 2019

AbstractThe photoluminescence spectra due to Er ions doped in a-Si:H were decomposed into several lines. The 19-K spectrum was reproduced by adding four Gaussian lines whose linewidths were increased with decreasing the photon energy. Since only the lowest energy level of 4I13/2 contributes to the radiative transition at this low temperature, the energy levels in 4I15/2 split by the Stark effect can be determined. These splittings are not largely different from those for Er in aluminosilicate glass. This implies that the all nearest neighbors of Er are oxygens which have been introduced unintentionally in the sample during preparation. The change in the photoluminescence intensity by annealing is discussed in relation with the spectral change and the results of ESR measurements.
Characterization of Amorphous Silicon by Secondary Ion Mass Spectrometry
Authors: Li Yupu , Wang Shaw , Lin Xue-Feng , Wei Luncun 
Published: June 2019

AbstractBased on various implanted standards, we have used SIMS (Secondary Ion Mass Spectrometry) to characterize amorphous Si thin films with high hydrogen content. SIMS and HFS (Hydrogen Forward Scattering) showed good agreement on the measured total H doses for H-implanted Si samples and the a-Si thin films. For the H-implanted Si samples, in the dose range of 2e15 atoms/cm2 to 2e17 atoms/cm2 (corresponding to peak H concentration from 0.32 at.% to 32 at.%), SIMS results showed that the calibration curve is a straight line. In other words, no correction for SIMS quantification is needed when moving from low to high hydrogen content samples. Analysis of P (Phosphorus) in a-Si thin films requires the use of high mass resolution magnetic sector SIMS to separate P and a mass interference from (30Si+H). Using a magnetic sector SIMS instrument, P-doped a-Si thin layers (˜ 50nm thick) were analyzed using 3keV O2 beam with oxygen leak for better depth resolution and improved detection limits. For the analysis of C, N, O in a-Si thin films (again approximately 50nm thick) the profiling energy typically needs to be lowered down to 3keV and the material needs to be sputtered at a high rate in order to reach real background levels. In this work, a-Si thin films were also analyzed using a 3keV Cs+ primary ion beam with (Cs2M)+ (M= C, N, O) detection for good depth resolution and detection limits.
High Density Plasma Processing of Microcrystalline Si Thin Films
Authors: Joshi P. C. , Voutsas A. T. , Hartzell J. W. 
Published: June 2019

AbstractIn the present work, we report on the fabrication of high quality microcrystalline Si thin films by high-density PECVD technique. The typical deposition rate of the HD-PECVD μ-Si thin films was greater than 350 Å/min in the H2/SiH4 ratio range of 20-100. For a 150-nm-thick film deposited at a H2/SiH4 ratio of 20, the typical microcrystalline volume fraction and the average crystallite size corresponding to <111> orientation were 75% and 160 Å, respectively. The observed growth and properties of the μ-Si thin films show the potential of the high-density PECVD technique for the low temperature processing of high quality films with superior control of bulk and interfacial characteristics.
Suppression of nucleation during the aluminum-induced layer exchange process
Authors: Schneider Jens , Klein Juliane , Sarikov Andrey , Muske Martin , Gall Stefan , Fuhs Walther 
Published: June 2019

AbstractFormation of polycrystalline silicon (poly-Si) thin films on inexpensive glass substrates is of great interest for large area electronic devices. Large grain sizes are desirable to reduce grain boundary effects. In the aluminum-induced layer exchange process Al/a-Si bi-layers exchange their positions with a concurrent crystallization of the amorphous Si (a-Si) in a simple annealing step. The process is characterized by the self regulated suppression of nucleation by existing grains resulting in large grain sizes above 10 μm. This paper elucidates the process within the Al Si phase diagram. The change in Si concentration within the Al is shown to cause the nucleation suppression.
Application of Field-Enhanced Rapid Thermal Annealing to Activation of Doped Polycrystalline Si Thin Films
Authors: So B.S. , You Y.H. , Kim H.J. , Kim Y.H. , Hwang J.H. , Shin D.H. , Ryu S.R. , Choi K. , Kim Y.C. 
Published: June 2019

AbstractActivation of polycrystalline silicon (poly-Si) thin films doped as n-type using selective ion implantation of phosphorous was performed employing field-enhanced rapid thermal annealing where rapid thermal annealing of halogen lamps is combined with alternating magnetic fields. The ion activation was evaluated using Hall effect measurements incorporating the resistivity, the charge carrier concentration, and the mobility. Statistical design of experiments is attempted in order to clarify the effects and interactions of processes variables on field-enhanced rapid thermal annealing towards ion activation: the three processing variables are furnace temperature, power of halogen lamp, and the alternating magnetic field. Hall effect measurements indicate that the furnace temperature and RTA power are found to be dominant in activating the doped polycrystalline Si in dose. The activation process results from the competition between charge carrier concentration and mobility: the increase in mobility is larger than the decrease in charge carrier concentration.
Use of Transparent Conductive Oxide Materials with Low Indices of Refraction in Amorphous Silicon-Based Solar Cell Technology
Authors: Jones Scott J. , Doehler Joachim , Liu Tongyu , Tsu David , Steele Jeff , Capangpangan Rey , Izu Masat 
Published: June 2019

AbstractNew types of transparent conductive oxides with low indices of refraction have been developed for use in optical stacks for the amorphous silicon (a-Si) solar cell and other thin film applications. The alloys are ZnO based with Si and MgF added to reduce the index of the materials through the creation of SiO2 or MgF2, with n=1.3-1.4, or the addition of voids in the materials. Alloys with 12-14% Si or Mg have indices of refraction at λ=800nm between 1.6 and 1.7. These materials are presently being used in optical stacks to enhance light scattering by Al/multi-layer/ZnO back reflectors in a-Si based solar cells to increase light absorption in the semiconductor layers and increase open circuit currents and boost device efficiencies. In contrast to Ag/ZnO back reflectors which have long term stability issues due to electromigration of Ag, these Al based back reflectors should be stable and usable in manufactured PV products. In this manuscript, structural properties for the materials will be reported as well as the performance of solar cell devices made using these new types of materials.