First-Principles Determination of Ultrahigh Thermal Conductivity of Boron Arsenide: A Competitor for Diamond?
Explore the source record for details and available documents.
charge transport↗
SEARCH · Engineering Papers
Results for “ARSENIDES”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Model for transport and reaction of defects and carriers within displacement cascades in gallium arsenide
A model is presented for recombination of charge carriers at evolving displacement damage in gallium arsenide, which includes clustering of the defects in atomic displacement cascades produced by neutron or ion irradiation. The carrier recombination model is based on an atomistic description of capture and emission of carriers by the defects with time evolution resulting from the migration and reaction of the defects. The physics and equations on which the model is based are presented, along with the details of the numerical methods used for their solution. The model uses a continuum description of diffusion, field-drift and reaction of carriers, and defects within a representative spherically symmetric cluster of defects. The initial radial defect profiles within the cluster were determined through pair-correlation-function analysis of the spatial distribution of defects obtained from the binary-collision code MARLOWE, using recoil energies for fission neutrons. Properties of the defects are discussed and values for their parameters are given, many of which were obtained from density functional theory. The model provides a basis for predicting the transient response of III-V heterojunction bipolar transistors to displacement damage from energetic particle irradiation.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Thermal and thermoelectric transport measurements of an individual boron arsenide microstructure
Recent first principles calculations have predicted that boron arsenide (BAs) can possess an unexpectedly high thermal conductivity that depends sensitively on the crystal size and defect concentration. However, few experimental results have been obtained to verify these predictions. In the present work, we report four-probe thermal and thermoelectric transport measurements of an individual BAs microstructure that was synthesized via a vapor transport method. The measured thermal conductivity was found to decrease slightly with temperature in the range between 250K and 350 K. The temperature dependence suggests that the extrinsic phonon scattering processes play an important role in addition to intrinsic phonon-phonon scattering. The room temperature value of (186646) Wm -1 K -1 is higher than that of bulk silicon but still a factor of four lower than the calculated result for a defect-free, non-degenerate BAs rod with a similar diameter of 1.15 μm. The measured p-type Seebeck coefficient and thermoelectric power factor are comparable to those of bismuth telluride, which is a commonly used thermoelectric material. In conclusion, the foregoing results also suggest that it is necessary to not only reduce defect and boundary scatterings but also to better understand and control the electron scattering of phonons in order to achieve the predicted ultrahigh intrinsic lattice thermal conductivity of BAs.
36 MATERIALS SCIENCE↗
The comparison between gallium arsenide and indium gallium arsenide as materials for solar cell performance using Silvaco application
The work presented in this paper is about the development of single and multilayer solar cells using GaAs and InGaAs in AM1.5 condition. The study includes the modeling structure and simulation of the device using Silvaco applications. The performance in term of efficiency of Indium Gallium Arsenide (InGaAs) and GaAs material was studied by modification of the doping concentration and thickness of material in solar cells. The efficiency of the GaAs solar cell was higher than InGaAs solar cell for single layer solar cell. Single layer GaAs achieved an efficiency about 25% compared to InGaAs which is only 2.65% of efficiency. For multilayer which includes both GaAs and InGaAs, the output power, P{sub max} was 8.91nW/cm² with the efficiency only 8.51%. GaAs is one of the best materials to be used in solar cell as a based compared to InGaAs.
30 DIRECT ENERGY CONVERSION↗
Outdoor Performance of a Thin-Film Gallium-Arsenide Photovoltaic Module
We deployed a 855 cm2 thin-film, single-junction gallium arsenide (GaAs) photovoltaic (PV) module outdoors. Due to its fundamentally different cell technology compared to silicon (Si), the module responds differently to outdoor conditions. On average during the test, the GaAs module produced more power when its temperature was higher. We show that its maximum-power temperature coefficient, while actually negative, is several times smaller in magnitude than that of a Si module used for comparison. The positive correlation of power with temperature in GaAs is due to temperature-correlated changes in the incident spectrum. We show that a simple correction based on precipitable water vapor (PWV) brings the photocurrent temperature coefficient into agreement with that measured by other methods and predicted by theory. The low operating temperature and small temperature coefficient of GaAs give it an energy production advantage in warm weather.
14 SOLAR ENERGY↗
Universal Heat Conduction in the Iron Arsenide Superconductor KFe 2 As 2 : Evidence of a d -Wave State
Not Available
Reid, J. -Ph.↗
Structural and physical properties of layered oxy-arsenides LnRuAsO (Ln=La, Nd, Sm, Gd)
Polycrystalline samples of LaRuAsO, NdRuAsO, SmRuAsO, and GdRuAsO have been synthesized and studied using powder x-ray diffraction, electrical transport, magnetization, and heat capacity measurements. Variations in structural properties across the series reveal a trend toward more ideal tetrahedral coordination around Ru as the size of the rare earth element is reduced. The lattice parameters of these Ru compounds show a more anisotropic response to variation in Ln than their Fe analogs, and significant anisotropy in thermal expansion is also observed. Transport measurements show metallic behavior, and carrier concentrations near 10{sup 21}-10{sup 22} electrons per cm{sup 3} are inferred from simple analysis of Hall effect measurements. Anomalies in resistivity, magnetization, and heat capacity indicate antiferromagnetic ordering of rare earth moments at 5 K for GdRuAsO, 4.5 K for SmRuAsO, and <2K for NdRuAsO. Magnetization measurements on LaRuAsO show no evidence of a magnetic moment on Ru. Observed behaviors are compared to those reported for similar Fe and Ru compounds. - Graphical abstract: Analysis of crystal structure, electrical transport, magnetic susceptibility, and heat capacity of LaRuAsO, NdRuAsO, SmRuAsO, and GdRuAsO. Highlights: Black-Right-Pointing-Pointer Experimental investigation of LaRuAsO, NdRuAsO, SmRuAsO, and GdRuAsO. Black-Right-Pointing-Pointer Anisotropic lattice response to changing Ln radius and temperature. Black-Right-Pointing-Pointer Ru coordination becomes more ideal as Ln radius is reduced. Black-Right-Pointing-Pointer Transport measurements reveal metallic conduction dominated by electrons. Black-Right-Pointing-Pointer Magnetic measurements indicate antiferromagnetic ordering Nd, Sm, and Gd moments.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Anomalous vibrational properties of cubic boron arsenide
Explore the source record for details and available documents.
charge transport↗
Inelastic Neutron Scattering Study of a Nonmagnetic Collapsed Tetragonal Phase in Nonsuperconducting CaFe2As2: Evidence of the Impact of Spin Fluctuations on Superconductivity in the Iron-Arsenide Compounds
The relationship between antiferromagnetic spin fluctuations and superconductivity has become a central topic of research in studies of superconductivity in the iron pnictides. We present unambiguous evidence of the absence of magnetic fluctuations in the nonsuperconducting collapsed tetragonal phase of CaFe2As2 via inelastic neutron scattering time-of-flight data, which is consistent with the view that spin fluctuations are a necessary ingredient for unconventional superconductivity in the iron pnictides. We demonstrate that the collapsed tetragonal phase of CaFe2As2 is nonmagnetic, and discuss this result in light of recent reports of high-temperature superconductivity in the collapsed tetragonal phase of closely related compounds.
36 MATERIALS SCIENCE↗
Local Orthorhombicity in the Magnetic C 4 Phase of the Hole-Doped Iron-Arsenide Superconductor Sr 1 - x Na x Fe 2 As 2
We report on temperature-dependent pair distribution function measurements of Sr 1-x Na x Fe 2 As 2 , an iron-based superconductor system that contains a magnetic phase with reentrant tetragonal symmetry, known as the magnetic C 4 phase. Quantitative refinements indicate that the instantaneous local structure in the C 4 phase comprises fluctuating orthorhombic regions with a length scale of similar to 2 nm, despite the tetragonal symmetry of the average static structure. Additionally, local orthorhombic fluctuations exist on a similar length scale at temperatures well into the paramagnetic tetragonal phase. Furthermore, these results highlight the exceptionally large nematic susceptibility of iron-based superconductors and have significant implications for the magnetic C 4 phase and the neighboring C 2 and superconducting phases.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
LARGE ACOUSTOELECTRIC EFFECT IN WAFER BONDED INDIUM GALLIUM ARSENIDE / LITHIUM NIOBATE HETEROSTRUCTURE AUGMENTED BY NOVEL GATE CONTROL.
Abstract not provided.
Siddiqui, Aleem↗
Gallium arsenide thermal conductivity and optical phonon relaxation times from first-principles calculations
Thermal conductivity of crystalline GaAs is calculated using first-principles lattice dynamics. The harmonic and cubic force constants are obtained by fitting them to the force-displacement data from density functional theory calculations. Phonon dispersion is calculated from a dynamical matrix constructed using the harmonic force constants and phonon relaxation times are calculated using Fermi's Golden rule. The calculated GaAs thermal conductivity agrees well with experimental data. Thermal conductivity accumulations as a function of the phonon mean free path and as a function of the wavelength are obtained. Our results predict a significant size effect on the GaAs thermal conductivity in the nanoscale. Relaxation times of optical phonons and their contributions from different scattering channels are also studied. Such information will help the understanding of hot phonon effects in GaAs-based devices.
42 ENGINEERING↗
Quaternary rare-earth arsenides REAg{sub 1−x}Zn{sub y}As{sub 2} (RE=La–Nd, Sm, Gd–Dy) with tetragonal SrZnBi{sub 2}- and HfCuSi{sub 2}-type structures
Reactions of the elements at 800 °C with the nominal compositions REAg{sub 1−x}Zn{sub x}As{sub 2} resulted in quaternary arsenides REAg{sub 1−x}Zn{sub y}As{sub 2} in which the combined Ag and Zn content deviates increasingly from unity in the Zn-richer phases, reflecting the transition from the fully stoichiometric ternary silver-containing arsenides REAgAs{sub 2} to the substoichiometric zinc-containing ones REZn{sub 0.67}As{sub 2}. Powder X-ray diffraction analysis indicated SrZnBi{sub 2}-type (space group I4/mmm, Z=4; RE=La, Ce) and HfCuSi{sub 2}-type structures (space group P4/nmm, Z=2; RE=Pr, Nd, Sm, Gd, Tb, Dy). Single-crystal X-ray diffraction analysis performed on LaAg{sub 0.5}Zn{sub 0.5}As{sub 2}, PrAg{sub 0.5}Zn{sub 0.5}As{sub 2}, and NdAg{sub 0.5}Zn{sub 0.5}As{sub 2} indicated that the Ag and Zn atoms are disordered within metal-centred tetrahedra and provided no evidence for distortion of the square As nets. The small electron excess tolerated in these quaternary arsenides and the absence of distortion in the square nets can be traced to the occurrence of As–As states that are only weakly antibonding near the Fermi level. PrAg{sub 0.5}Zn{sub 0.5}As{sub 2} and NdAg{sub 0.5}Zn{sub 0.5}As{sub 2} are paramagnetic with effective magnetic moments consistent with trivalent RE species. - Graphical abstract: On proceeding from fully stoichiometric REAgAs{sub 2} to substoichiometric REZn{sub 0.67}As{sub 2}, deficiencies in Zn content become increasingly prominent in quaternary arsenides REAg{sub 1−x}Zn{sub y}As{sub 2}. - Highlights: • Ag and Zn atoms are disordered within quaternary arsenides REAg{sub 1−x}Zn{sub y}As{sub 2}. • In Zn-richer phases, Zn deficiencies develop to counteract electron excess. • Distortions of square As net appear to be suppressed.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Continuous injection synthesis of indium arsenide quantum dots emissive in the short-wavelength infrared
With the emergence of applications based on short-wavelength infrared light, indium arsenide quantum dots are promising candidates to address existing shortcomings of other infrared-emissive nanomaterials. However, III–V quantum dots have historically struggled to match the high-quality optical properties of II–VI quantum dots. Here we present an extensive investigation of the kinetics that govern indium arsenide nanocrystal growth. Based on these insights, we design a synthesis of large indium arsenide quantum dots with narrow emission linewidths. We further synthesize indium arsenide-based core-shell-shell nanocrystals with quantum yields up to 82% and improved photo- and long-term storage stability. We then demonstrate non-invasive through-skull fluorescence imaging of the brain vasculature of murine models, and show that our probes exhibit 2–3 orders of magnitude higher quantum yields than commonly employed infrared emitters across the entire infrared camera sensitivity range. Finally, we anticipate that these probes will not only enable new biomedical imaging applications, but also improved infrared nanocrystal-LEDs and photon-upconversion technology.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Niobium-bearing arsenides and germanides from elemental mixtures not involving niobium: a new twist to an old problem in solid-state synthesis
Three isostructural transition-metal arsenides and germanides, namely niobium nickel arsenide, Nb 0.92(1) NiAs, niobium cobalt arsenide, NbCoAs, and niobium nickel germanide, NbNiGe, were obtained as inadvertent side products of high-temperature reactions in sealed niobium containers. In addition to reporting for the very first time the structures of the title compounds, refined from single-crystal X-ray diffraction data, this article also serves as a reminder that niobium containers may not be suitable for the synthesis of ternary arsenides and germanides by traditional high-temperature reactions. Synthetic work involving alkali or alkaline-earth metals, transition or early post-transition metals, and elements from groups 14 or 15 under such conditions may yield Nb-containing products, which at times could be the major products of such reactions.
Chemistry↗
Basal-plane growth of cadmium arsenide by molecular beam epitaxy
(001)-oriented thin films of the three-dimensional Dirac semimetal cadmium arsenide can realize a quantum spin Hall insulator and other kinds of topological physics, all within the flexible architecture of epitaxial heterostructures. Here, we report a method for growing (001) cadmium arsenide films using molecular beam epitaxy. The introduction of a thin indium arsenide wetting layer improves surface morphology and structural characteristics, as measured by x-ray diffraction and reflectivity, atomic force microscopy, and scanning transmission electron microscopy. The electron mobility of 50-nm-thick films is found to be 9300cm 2 /Vs at 2 K, comparable to the highest-quality films grown in the conventional (112) orientation. This work demonstrates a simple experimental framework for exploring topological phases that are predicted to exist in proximity to the three-dimensional Dirac semimetal phase.
36 MATERIALS SCIENCE↗
Ternary arsenides ATt{sub 3}As{sub 3} (A=K, Rb; Tt=Ge, Sn) with layered structures
The four ternary arsenides ATt{sub 3}As{sub 3} (A=K, Rb; Tt=Ge, Sn) were obtained by reaction of the elements at 600–650 °C. They adopt an orthorhombic structure (space group Pnma, Z=4, with cell parameters ranging from a=9.9931(11) Å, b=3.7664(4) Å, c=18.607(2) Å for KGe{sub 3}As{sub 3} to a=10.3211(11) Å, b=4.0917(4) Å, c=19.570(2) Å for RbSn{sub 3}As{sub 3}) containing corrugated [Tt{sub 3}As{sub 3}] layers built from Tt-centred trigonal pyramids and tetrahedra forming five-membered rings decorated with As handles. They can be considered to be Zintl phases with Tt atoms in +4, +3, and +1 oxidation states. Band structure calculations predict that these compounds are semiconductors with narrow band gaps (0.71 eV in KGe{sub 3}As{sub 3}, 0.50 eV in KSn{sub 3}As{sub 3}). - Graphical abstract: Ternary arsenides ATt{sub 3}As{sub 3} (A=K, Rb; Tt=Ge, Sn) contain corrugated layers with Tt atoms in three different oxidation states and are narrow band gap semiconductors. Display Omitted - Highlights: • ATt{sub 3}As{sub 3} (A=K, Rb; Tt=Ge, Sn) contains Tt atoms in three oxidation states. • The structure differs from NaGe{sub 3}P{sub 3} in terms of layer stacking arrangement. • The compounds are predicted to be narrow band gap semiconductors.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Revealing the optoelectronic and thermoelectric properties of the Zintl quaternary arsenides ACdGeAs{sub 2} (A = K, Rb)
Highlights: • Zintl tetragonal phase ACdGeAs{sub 2} (A = K, Rb) are chalcopyrite and semiconductors. • Their direct band gap is suitable for PV, optolectronic and thermoelectric applications. • Combination of DFT and Boltzmann transport theory is employed. • The present arsenides are found to be covalent materials. - Abstract: Chalcopyrite semiconductors have attracted much attention due to their potential implications in photovoltaic and thermoelectric applications. First principle calculations were performed to investigate the electronic, optical and thermoelectric properties of the Zintl tetragonal phase ACdGeAs{sub 2} (A = K, Rb) using the full potential linear augmented plane wave method and the Engle–Vosko GGA (EV–GGA) approximation. The present compounds are found semiconductors with direct band gap and covalent bonding character. The optical transitions are investigated via the dielectric function (real and imaginary parts) along with other related optical constants including refractive index, reflectivity and energy-loss spectrum. Combining results from DFT and Boltzmann transport theory, we reported the thermoelectric properties such as the Seebeck’s coefficient, electrical and thermal conductivity, figure of merit and power factor as function of temperatures. The present chalcopyrite Zintl quaternary arsenides deserve to be explored for their potential applications as thermoelectric materials and for photovoltaic devices.
36 MATERIALS SCIENCE↗