The Experts below are selected from a list of 2445 Experts worldwide ranked by ideXlab platform
Burkhard Dünweg - One of the best experts on this subject based on the ideXlab platform.
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structural properties of si 1 x ge x Alloys a monte carlo simulation with the stillinger weber potential
Physical Review B, 1995Co-Authors: Mohamed Laradji, David P. Landau, Burkhard DünwegAbstract:The structural properties of binary silicon-Germanium Alloys are investigated by means of large-scale constant-pressure Monte Carlo simulations of the Stillinger-Weber model. At low temperatures, the binary-mixture phase separates into Si-rich and Ge-rich phases. The two-phase coexistence region is terminated by a critical point that belongs to the mean-field universality class. We also studied the structural properties of pure Si and Ge as well as the binary mixture. In particular, we found that the linear thermal expansions for both Si and Ge are in agreement with experiments, and that V\'egard's law is valid at temperatures above the critical point. Finally, we compare the bond-length and bond-angle distributions with earlier analytical and numerical calculations based on the Kirkwood potential.
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A Monte Carlo Simulation of the Stillinger-Weber Model for Si-Ge Alloys
MRS Proceedings, 1994Co-Authors: Mohamed Laradji, David P. Landau, Burkhard DünwegAbstract:The bulk phase behavior of silicon-Germanium Alloys is investigated by means of a constant pressure Monte Carlo simulation of the Stillinger-Weber potential in the semi-grand-canonical ensemble. At low temperatures, Si and Ge phase separate into a Si-rich phase and a Ge-rich phase. The two-phase region is terminated by a critical point whose nature is investigated thoroughly by the multihistogram method combined with finite size scaling analysis. These results showed that the critical behavior of the alloy belongs to the mean field universality class, presumably due to the elastic degrees of freedom. We have also studied the structural properties of the mixture and found that the linear thermal expansions of both Si and Ge agree well with experiments. We also verified Vegard's law above the critical point and calculated bond length distributions.
Joseph S Poon - One of the best experts on this subject based on the ideXlab platform.
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ballistic transport of long wavelength phonons and thermal conductivity accumulation in nanograined silicon Germanium Alloys
Applied Physics Letters, 2017Co-Authors: Long Chen, Jeffrey L Braun, Brian F Donovan, Patrick E Hopkins, Joseph S PoonAbstract:Computationally efficient modeling of the thermal conductivity of materials is crucial to thorough experimental planning and theoretical understanding of thermal properties. We present a modeling approach in this work that utilizes a frequency-dependent effective medium theory to calculate the lattice thermal conductivity of nanostructured solids. This method accurately predicts a significant reduction in the experimentally measured thermal conductivity of nanostructured Si80Ge20 systems reported in this work, along with previously reported thermal conductivities in nanowires and nanoparticles in matrix materials. We use our model to gain insights into the role of long wavelength phonons on the thermal conductivity of nanograined silicon-Germanium Alloys. Through thermal conductivity accumulation calculations with our modified effective medium model, we show that phonons with wavelengths much greater than the average grain size will not be impacted by grain boundary scattering, counter to the traditionall...
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ballistic transport of long wavelength phonons and thermal conductivity accumulation in nanograined silicon Germanium Alloys
arXiv: Mesoscale and Nanoscale Physics, 2017Co-Authors: Long Chen, Jeffrey L Braun, Brian F Donovan, Patrick E Hopkins, Joseph S PoonAbstract:Computationally efficient modeling of the thermal conductivity of materials is crucial to thorough experimental planning and theoretical understanding of thermal properties. We present a modeling approach in this work that utilizes frequency-dependent effective medium to calculate lattice thermal conductivity of nanostructured solids. The method accurately predicts a significant reduction in the thermal conductivity of nanostructured Si80Ge20 systems, along with previous reported thermal conductivities in nanowires and nanoparticles-in-matrix materials. We use our model to gain insight into the role of long wavelength phonons on the thermal conductivity of nanograined silicon-Germanium Alloys. Through thermal conductivity accumulation calculations with our modified effective medium model, we show that phonons with wavelengths much greater than the average grain size will not be impacted by grain boundary scattering, counter to the traditionally assumed notion that grain boundaries in solids will act as diffusive interfaces that will limit long wavelength phonon transport. This is further supported through a modulation frequency dependent thermal conductivity as measured with time-domain thermoreflectance.
Long Chen - One of the best experts on this subject based on the ideXlab platform.
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ballistic transport of long wavelength phonons and thermal conductivity accumulation in nanograined silicon Germanium Alloys
Applied Physics Letters, 2017Co-Authors: Long Chen, Jeffrey L Braun, Brian F Donovan, Patrick E Hopkins, Joseph S PoonAbstract:Computationally efficient modeling of the thermal conductivity of materials is crucial to thorough experimental planning and theoretical understanding of thermal properties. We present a modeling approach in this work that utilizes a frequency-dependent effective medium theory to calculate the lattice thermal conductivity of nanostructured solids. This method accurately predicts a significant reduction in the experimentally measured thermal conductivity of nanostructured Si80Ge20 systems reported in this work, along with previously reported thermal conductivities in nanowires and nanoparticles in matrix materials. We use our model to gain insights into the role of long wavelength phonons on the thermal conductivity of nanograined silicon-Germanium Alloys. Through thermal conductivity accumulation calculations with our modified effective medium model, we show that phonons with wavelengths much greater than the average grain size will not be impacted by grain boundary scattering, counter to the traditionall...
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ballistic transport of long wavelength phonons and thermal conductivity accumulation in nanograined silicon Germanium Alloys
arXiv: Mesoscale and Nanoscale Physics, 2017Co-Authors: Long Chen, Jeffrey L Braun, Brian F Donovan, Patrick E Hopkins, Joseph S PoonAbstract:Computationally efficient modeling of the thermal conductivity of materials is crucial to thorough experimental planning and theoretical understanding of thermal properties. We present a modeling approach in this work that utilizes frequency-dependent effective medium to calculate lattice thermal conductivity of nanostructured solids. The method accurately predicts a significant reduction in the thermal conductivity of nanostructured Si80Ge20 systems, along with previous reported thermal conductivities in nanowires and nanoparticles-in-matrix materials. We use our model to gain insight into the role of long wavelength phonons on the thermal conductivity of nanograined silicon-Germanium Alloys. Through thermal conductivity accumulation calculations with our modified effective medium model, we show that phonons with wavelengths much greater than the average grain size will not be impacted by grain boundary scattering, counter to the traditionally assumed notion that grain boundaries in solids will act as diffusive interfaces that will limit long wavelength phonon transport. This is further supported through a modulation frequency dependent thermal conductivity as measured with time-domain thermoreflectance.
Gautam Ganguly - One of the best experts on this subject based on the ideXlab platform.
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improvement of hydrogenated amorphous silicon Germanium Alloys using low power disilane germane discharges without hydrogen dilution
Applied Physics Letters, 1995Co-Authors: Akihisa Matsuda, Gautam GangulyAbstract:We suggest that the role of hydrogen dilution in the improvement of the quality of hydrogenated amorphous silicon Germanium Alloys is to alter the relative contribution of the short and long lifetime precursors to film growth which are deleterious and beneficient, respectively. In order to circumvent the preferential depletion of germane when mixed with silane, we have used low power disilane–germane discharges and thereby obtained films with an optical gap <1.5 eV having similar Urbach tail width and defect absorption, with and without hydrogen dilution.
David J Cohen - One of the best experts on this subject based on the ideXlab platform.
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junction capacitance study of an oxygen impurity defect exhibiting configuration relaxation in amorphous silicon Germanium Alloys deposited by hot wire cvd
Journal of Non-crystalline Solids, 2008Co-Authors: Shouvik Datta, David J Cohen, A H Mahan, Howard M BranzAbstract:Abstract We report the observation of light induced electron capture in oxygen contaminated (∼5 × 1020 cm−3) hydrogenated amorphous silicon–Germanium Alloys grown by hot-wire chemical vapor deposition (HWCVD). By examining the time evolution of dark capacitance after 1.2 eV photoexcitation, we are able to estimate the free energy barrier (⩾0.8 eV) for the release of electrons into the conduction band. Such a large thermal barrier, for a defect whose optical threshold is centered (∼1.35 eV) so close to the band-gap (1.5 eV), indicates significant configurational relaxation once the oxygen impurity state is occupied with photoexcited electrons.
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light induced defects in hydrogenated amorphous silicon Germanium Alloys
Solar Energy Materials and Solar Cells, 2003Co-Authors: David J CohenAbstract:Abstract A selected survey of the phenomenon of light-induced deep defect creation in the hydrogenated amorphous silicon–Germanium is presented. First a general review of the early studies that established the key salient features of light-induced degradation in a-Si,Ge:H is given. This is followed by a discussion of a couple of complicating issues that have more recently come to light; namely, the possibility that charged defects play a more central role in the Alloys, and that both Si and Ge metastable dangling bonds may be playing a significant role in the Alloys with Germanium fractions below 20 at%. Following this, the results of some recent studies are summarized that have been focusing on the details of degradation in the low Ge fraction Alloys to gain insight into the fundamentals of degradation of amorphous silicon materials in general. This review concludes with an overall assessment of the level of our understanding of degradation in the a-Si,Ge:H Alloys and where some key issues are still remaining to be resolved.