The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Qingyang Fan - One of the best experts on this subject based on the ideXlab platform.
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Physical properties of Si-Ge Alloys in C2/m phase: a comprehensive investigation.
Journal of physics. Condensed matter : an Institute of Physics journal, 2019Co-Authors: Yanxing Song, Qingyang Fan, Wei Zhang, Changchun Chai, Yintang YangAbstract:A new phase of C2/m Ge16 is first proposed in this paper. The structures and mechanical, anisotropic, electronic, transport and optical properties of Si-Ge Alloys in the C2/m phase are studied using first principles calculations. All Ge16 and Si16-x Ge x Alloys in the C2/m phase are proven to have mechanical and dynamic stability. By analyzing the three-dimensional (3D) perspective of the effective mass and Young's modulus, obvious anisotropies of transport and mechanical properties are found. Higher-resolution full band structures are obtained to determine the positions of the valence band maximum (VBM) and conduction band minimum (CBM). All materials have a higher photoelectron absorption than that of diamond Si. A high electronic mobility (16 527 cm2 V-1 s-1) and hole mobility (3033 cm2 V-1 s-1) are found in C2/m Si8Ge8 and Si4Ge12, respectively. Based on the large mobility and photoelectron absorption, the Si-Ge Alloys in the C2/m phase are promising materials for electronics and optoelectronics applications.
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t si64 a novel silicon allotrope
ChemPhysChem, 2019Co-Authors: Qingyang Fan, Rui Niu, Wenzhu Zhang, Wei Zhang, Yingchun Ding, Sining YunAbstract:Utilizing first principle calculations, a novel Si64 silicon allotrope in the I41 /amd space group with tetragonal symmetry (denoted as t-Si64 below) is proposed in this work. In addition, also its structural, anisotropic mechanical, and electronic properties along with its minimum thermal conductivity κmin were predicted. The mechanical and thermodynamic stability of t-Si64 were evaluated by means of elastic constants and phonon spectra. The electronic band structure indicates that t-Si64 is an indirect band gap semiconductor with a band gap: 0.67 eV (primitive cell) compared to a direct band gap of 0.70 eV with respect to a conventional cell. The minimum thermal conductivity of t-Si64 (0.74 W cm-1 K-1 ) is much smaller than that of diamond silicon (1.13 W cm-1 K-1 ). Therefore, Si-Ge Alloys in the I41 /amd space group are potential thermoelectric materials.
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Si–Ge Alloys in C2/c phase with tunable direct band gaps: A comprehensive study
Current Applied Physics, 2019Co-Authors: Qingyang Fan, Wenzhu Zhang, Wei Zhang, Yanxing Song, Huiqin Wang, Mingfei Wei, Sining YunAbstract:Abstract Si–Ge Alloys are a new type of semiconductor material that are of great significance for the development of microelectronic technology, especially in the photoelectricity industry and for thermoelectric conversion in high temperature applications (>700 K). In the present work, a novel Ge allotrope in the C2/c phase with band gap of 1.102 eV was firstly proposed, which is suitable for the absorption of sunlight. C2/c-Ge are mechanically, dynamically and thermodynamically stable. A series of Si24-xGex Alloys (x = 0, 8, 16, 24) in the C2/c phase with band gaps of 1.10–1.50 eV are predicted by ab initio calculations at ambient conditions. The Si24-xGex Alloys (x = 0, 8, 16, 24) in C2/c phase have better absorption ability than that of the Si in diamond, hP12 and oC12 phases. The Si24-xGex Alloys in the C2/c phase have the strong absorption in the visible, which have a great impact on the new-generation photovoltaic applications.
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Theoretical investigations of group IV Alloys in the Lonsdaleite phase
Journal of Materials Science, 2017Co-Authors: Qingyang Fan, Changchun Chai, Qun Wei, Kaiqiang Wong, Yuqian Liu, Yintang YangAbstract:The structural, elastic, elastic anisotropic, thermodynamic and electronic properties of Lonsdaleite C, Si and Ge and Lonsdaleite C–Si and Si–Ge Alloys are investigated using density functional theory. The elastic anisotropy calculations show that the Lonsdaleite C0.25Si0.75 alloy has the greatest anisotropy in Poisson’s ratio, shear modulus, bulk modulus and Young’s modulus. Through the mixing of carbon and silicon and silicon and germanium at certain proportions, Lonsdaleite C0.25Si0.75 with metallic properties and Lonsdaleite Si0.25Ge0.75 with a direct band gap are obtained, where Lonsdaleite Si0.25Ge0.75 is a narrow direct band gap semiconductor with a band gap of 0.76 eV at the HSE06 hybrid functional level. The minimum thermal conductivity calculations on Lonsdaleite C–Si and Si–Ge Alloys show that the minimum thermal conductivities of Lonsdaleite C0.75Si0.25 and Lonsdaleite C0.5Si0.5 are greater than that of diamond C, and the minimum thermal conductivities of Lonsdaleite C–Si and Si–Ge Alloys in different directions are also investigated.
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Prediction of novel phase of silicon and Si–Ge Alloys
Journal of Solid State Chemistry, 2016Co-Authors: Qingyang Fan, Changchun Chai, Qun Wei, Yintang Yang, Chen Pengyuan, Mengjiang Xing, Junqin Zhang, Ronghui YaoAbstract:Abstract The structural, thermodynamic, elastic, anisotropic and electronic properties of P2221-Si have been studied using first-principles calculations. The elastic constants are satisfied with mechanical stability criteria. The mechanical anisotropy is predicted by anisotropic constants Poisson's ratio, shear modulus, Young's modulus and three dimensional curved surface of Young's modulus. These results show that P2221-Si and Si–Ge Alloys are anisotropic. The sound velocities in different directions and Debye temperature for P2221-Si and Si–Ge Alloys are also predicted. Electronic structure study shows that P2221-Si is an indirect semiconductor with band gap of 0.90 eV. In addition, the band structures of Si–Ge Alloys are investigated in this paper. Finally, we also calculate the thermodynamics properties and obtained the relationships between thermal parameters and temperature.
Takao Miwa - One of the best experts on this subject based on the ideXlab platform.
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Silicon-germanium Alloys prepared by the heat treatment of silicon substrate spin-coated with organo-soluble germanium cluster
Materials Letters, 2000Co-Authors: Akira Watanabe, Masashi Unno, Fusao Hojo, Takao MiwaAbstract:Abstract A novel technique for obtaining Si–Ge Alloys using coating technique was developed, where an organo-soluble germanium cluster was spin-coated on a silicon substrate and the heat treatment of the substrate leads to the formation of a Si–Ge alloy on the substrate. The structural changes of the thin film and the silicon surface by alloying germanium into silicon were investigated by micro-Raman spectroscopy.
Yintang Yang - One of the best experts on this subject based on the ideXlab platform.
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Physical properties of Si-Ge Alloys in C2/m phase: a comprehensive investigation.
Journal of physics. Condensed matter : an Institute of Physics journal, 2019Co-Authors: Yanxing Song, Qingyang Fan, Wei Zhang, Changchun Chai, Yintang YangAbstract:A new phase of C2/m Ge16 is first proposed in this paper. The structures and mechanical, anisotropic, electronic, transport and optical properties of Si-Ge Alloys in the C2/m phase are studied using first principles calculations. All Ge16 and Si16-x Ge x Alloys in the C2/m phase are proven to have mechanical and dynamic stability. By analyzing the three-dimensional (3D) perspective of the effective mass and Young's modulus, obvious anisotropies of transport and mechanical properties are found. Higher-resolution full band structures are obtained to determine the positions of the valence band maximum (VBM) and conduction band minimum (CBM). All materials have a higher photoelectron absorption than that of diamond Si. A high electronic mobility (16 527 cm2 V-1 s-1) and hole mobility (3033 cm2 V-1 s-1) are found in C2/m Si8Ge8 and Si4Ge12, respectively. Based on the large mobility and photoelectron absorption, the Si-Ge Alloys in the C2/m phase are promising materials for electronics and optoelectronics applications.
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Theoretical investigations of group IV Alloys in the Lonsdaleite phase
Journal of Materials Science, 2017Co-Authors: Qingyang Fan, Changchun Chai, Qun Wei, Kaiqiang Wong, Yuqian Liu, Yintang YangAbstract:The structural, elastic, elastic anisotropic, thermodynamic and electronic properties of Lonsdaleite C, Si and Ge and Lonsdaleite C–Si and Si–Ge Alloys are investigated using density functional theory. The elastic anisotropy calculations show that the Lonsdaleite C0.25Si0.75 alloy has the greatest anisotropy in Poisson’s ratio, shear modulus, bulk modulus and Young’s modulus. Through the mixing of carbon and silicon and silicon and germanium at certain proportions, Lonsdaleite C0.25Si0.75 with metallic properties and Lonsdaleite Si0.25Ge0.75 with a direct band gap are obtained, where Lonsdaleite Si0.25Ge0.75 is a narrow direct band gap semiconductor with a band gap of 0.76 eV at the HSE06 hybrid functional level. The minimum thermal conductivity calculations on Lonsdaleite C–Si and Si–Ge Alloys show that the minimum thermal conductivities of Lonsdaleite C0.75Si0.25 and Lonsdaleite C0.5Si0.5 are greater than that of diamond C, and the minimum thermal conductivities of Lonsdaleite C–Si and Si–Ge Alloys in different directions are also investigated.
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Prediction of novel phase of silicon and Si–Ge Alloys
Journal of Solid State Chemistry, 2016Co-Authors: Qingyang Fan, Changchun Chai, Qun Wei, Yintang Yang, Chen Pengyuan, Mengjiang Xing, Junqin Zhang, Ronghui YaoAbstract:Abstract The structural, thermodynamic, elastic, anisotropic and electronic properties of P2221-Si have been studied using first-principles calculations. The elastic constants are satisfied with mechanical stability criteria. The mechanical anisotropy is predicted by anisotropic constants Poisson's ratio, shear modulus, Young's modulus and three dimensional curved surface of Young's modulus. These results show that P2221-Si and Si–Ge Alloys are anisotropic. The sound velocities in different directions and Debye temperature for P2221-Si and Si–Ge Alloys are also predicted. Electronic structure study shows that P2221-Si is an indirect semiconductor with band gap of 0.90 eV. In addition, the band structures of Si–Ge Alloys are investigated in this paper. Finally, we also calculate the thermodynamics properties and obtained the relationships between thermal parameters and temperature.
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Mechanical and electronic properties of Si, Ge and their Alloys in P42 /mnm structure
Materials Science in Semiconductor Processing, 2016Co-Authors: Qingyang Fan, Changchun Chai, Qun Wei, Mengjiang Xing, Peikun Zhou, Yintang YangAbstract:Abstract Structural, mechanical, and electronic properties of Si–Ge Alloys in P42/mnm structure were studied using first-principles calculations by Cambridge Serial Total Energy Package (CASTEP) plane-wave code. The calculations were performed with the local density approximation and generalized gradient approximation in the form of Perdew–Burke–Ernzerhof, PBEsol. The calculated excess mixing enthalpy is positive over the entire germanium composition range. The calculated formation enthalpy shows that the Si–Ge Alloys are unstable at 0 K; however, the Alloys might exist at specified high temperature scale. The anisotropic calculations show that Si12 in P42/mnm structure exhibits the greatest anisotropy in Poisson’s ratio, shear modulus, Young’s modulus and the universal elastic anisotropy index AU, but Si8Ge4 has the smallest anisotropy. The electronic structure calculations reveal that Si12 and Si–Ge Alloys in P42/mnm structure are indirect band gap semiconductors, but Ge12 in P42/mnm structure is a direct semiconductor.
Ulrich Dahmen - One of the best experts on this subject based on the ideXlab platform.
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Strain-compensated nano-clusters in Al-Si-Ge Alloys
Scripta Materialia, 2006Co-Authors: Velimir Radmilovic, David Mitlin, Michael K Miller, Ulrich DahmenAbstract:Abstract Atom probe tomography and high resolution transmission electron microscopy have been employed to reveal clustering of Si and Ge atoms in ternary Al–Si–Ge. No such clusters were observed in binary Al–Si. The clusters were on the order of five nanometers in diameter and contained Si, Ge and Al. This confirms a previous hypothesis that postulates the existence of such clusters due to atomic mismatch strain compensation between the Si and Ge atoms in an Al solid solution.
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On the influence of Si−Ge additions on the aging response of Al−Cu
Metallurgical and Materials Transactions A, 2003Co-Authors: David Mitlin, Velimir Radmilovic, J.w. Morris, Ulrich DahmenAbstract:Al−Cu−Si−Ge Alloys display a unique combination of ultrarapid aging response, high peak hardness, and extended-aging microstructural stability. The purpose of this work is to explain these properties in terms of the role that the Si−Ge additions have on modifying the conventional Al−Cu aging sequence. In both AlCu and AlCuSiGe, the room-temperature microstructure consists of both Guinier-Preston (GP) zones and ϕ″ precipitates. Upon aging at 190°C, Al−Cu displays the well-known precipitation sequence: the slow dissolution of GP zones and ϕ″ and the gradual formation of ϕ′. In the quaternary alloy, Si−Ge particles quickly nucleate and grow during elevated-temperature aging (they are detected after as little as 30 minutes at 190 °C). The Si−Ge particles then act as nucleation sites for ϕ′ precipitates, resulting in a peak-aged microstructure consisting of a dense distribution of ϕ′ attached to Si−Ge.
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On the influence of Si-Ge additions on the aging response of Al-Cu
Metallurgical and Materials Transactions A, 2003Co-Authors: David Mitlin, Velimir Radmilovic, Ulrich Dahmen, J.w. MorrisAbstract:Al-Cu-Si-Ge Alloys display a unique combination of ultrarapid aging response, high peak hardness, and extended-aging microstructural stability. The purpose of this work is to explain these properties in terms of the role that the Si-Ge additions have on modifying the conventional Al-Cu aging sequence. In both AlCu and AlCuSiGe, the room-temperature microstructure consists of both Guinier-Preston (GP) zones and ϑ ″ precipitates. Upon aging at 190 °C, Al-Cu displays the well-known precipitation sequence: the slow dissolution of GP zones and ϑ ″ and the gradual formation of ϑ ′. In the quaternary alloy, Si-Ge particles quickly nucleate and grow during elevated-temperature aging (they are detected after as little as 30 minutes at 190 °C). The Si-Ge particles then act as nucleation sites for ϑ ′ precipitates, resulting in a peak-aged microstructure consisting of a dense distribution of ϑ ′ attached to Si-Ge.
H.p. Wang - One of the best experts on this subject based on the ideXlab platform.
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Specific heat of ternary Ag–Si–Ge Alloys from 123 K to high temperatures: experiment and prediction
Journal of Thermal Analysis and Calorimetry, 2020Co-Authors: Qi Wang, H. M. Chen, D. L. Geng, H.p. WangAbstract:The knowledge of specific heat for Ag–Si–Ge Alloys in a broad temperature range would facilitate their practical applications in various branches of engineering. In this work, differential scanning calorimetry measurements were executed to determine specific heat of Ag–Si–Ge Alloys from 123 K to high temperatures. For binary Alloys, distinct troughs of specific heat are observed at eutectic Ag89Si11 and Ag75Ge25, when temperatures are larger than 500 K. Furthermore, specific heat of ternary Ag–Si–Ge Alloys was predicted by four candidate principles based on the binary alloy’s data. Accordingly, the specific heat of 15 compositions of ternary Ag–Si–Ge Alloys was determined to evaluate the predicted value. It is found that specific heat increases linearly with the rising Ag and Ge content in Si-rich Alloys at low temperatures. Besides, Alloys around Si–Ag75Ge25 pseudobinary line in Ag-rich area exhibit much lower specific heat at high temperatures. According to the comparison between measured and predicted specific heat of ternary Alloys, the interpolation which employs data of pure elements, hypo-/hypereutectic Alloys and the eutectic points, provides highest accuracy, especially at high temperatures. This rule may be applied to other eutectic systems.
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Thermophysical properties and atomic structure of liquid Si-Ge Alloys
Materials Chemistry and Physics, 2019Co-Authors: Q. Wang, J. Chang, H.p. WangAbstract:Abstract The thermophysical properties and atomic structure of liquid Si-Ge Alloys were investigated by the molecular dynamic simulations with Stillinger-Weber potential over a broad temperature range, including both superheating and undercooled regime. The maximum undercooling in this work is 611 K for pure Ge. For all the Si100-xGex (x = 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100) Alloys, the densities exhibit quadratic relationship with temperature. The density of Si at the melting temperature is 2.59 g·cm−3, existing a slight deviation of 0.39% compared with the experiential data. For liquid Ge, the density at the melting temperature is 5.62 g·cm−3, nearly identical with the reported values. In all the cases, the densities of Si-Ge Alloys with different compositions are larger than those of ideal solution. Therefore, liquid Si-Ge Alloys display negative excess volume, which reaches the minimum at 40% Ge content. The specific heat was obtained by thermodynamic function and energy fluctuation approaches, respectively. Both of the results are in good agreement with experimental data around the liquidus temperatures. Furthermore, the diffusion coefficients were obtained by calculating the mean square displacement. The pair distribution function was applied to analyze the liquid structure. It is found that the peaks occur around the liquidus temperatures, which implies the structure change between normal and undercooled liquid Alloys.