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Influence of doping on the dynamical properties of III–V–N by Raman scattering, infrared absorption and model calculations
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On the pressure-dependent phonon characteristics and anomalous thermal expansion coefficient of 3C-SiC
No full textSITE SELECTIVITY OF DEFECTS IN III-V COMPOUNDS BY LOCAL MODE SPECTROSCOPY AND MODEL CALCULATIONS
No full textComputational phonon dispersions structural and thermodynamical characteristics of novel C-based XC (X = Si, Ge and Sn) materials
No full textA realistic rigid-ion-model (RIM) is adopted here to report the results of systematic calculations for comprehending the phonon dispersionsωjq→, structural, and thermodynamic traits of novel zinc-blende group-IV binary XC (X = Si, Ge, and Sn) materials. At ambient pressure, our study of ωjq→ has offered positive values of the acoustic phonon frequencies in the entire Brillouin zone – implying the structural stability of these zinc-blende (zb) semiconductors. In the absence of experimental data for GeC and SnC on Born’s transverse effective charges eT*, T-dependent Debye temperatures ΘDT, specific heats CvT, and thermal expansion coefficients α(T), our predicted results are consistent with the existing ab initio calculations. Large deviations in ΘDT offered by a few authors are probably linked to their use of simple analytical expressions. In agreement with the first principles calculations on 3 C-SiC, our study has provided accurate T-dependent thermodynamic quantities. As compared to 3 C-SiC, we have predicted substantially lower (higher) ΘDT (α(T)) values for the zb GeC and zb SnC. Based on these outcomes, it is likely that these materials might not support the required criterion for their use as fuel cladding and/or structural materials in nuclear reactors. However, we strongly feel that these C-based compounds will be valuable in designing multi-quantum well and superlattice-based micro-/nano devices for different strategic and civilian applications needs
Composition-Dependent Phonon and Thermodynamic Characteristics of C-Based X<sub>x</sub>Y<sub>1−x</sub>C (X, Y ≡ Si, Ge, Sn) Alloys
No full textNovel zinc-blende (zb) group-IV binary XC and ternary XxY1−xC alloys (X, Y ≡ Si, Ge, and Sn) have recently gained scientific and technological interest as promising alternatives to silicon for high-temperature, high-power optoelectronics, gas sensing and photovoltaic applications. Despite numerous efforts made to simulate the structural, electronic, and dynamical properties of binary materials, no vibrational and/or thermodynamic studies exist for the ternary alloys. By adopting a realistic rigid-ion-model (RIM), we have reported methodical calculations to comprehend the lattice dynamics and thermodynamic traits of both binary and ternary compounds. With appropriate interatomic force constants (IFCs) of XC at ambient pressure, the study of phonon dispersions ωjq→ offered positive values of acoustic modes in the entire Brillouin zone (BZ)—implying their structural stability. For XxY1−xC, we have used Green’s function (GF) theory in the virtual crystal approximation to calculate composition x, dependent ωjq→ and one phonon density of states gω. With no additional IFCs, the RIM GF approach has provided complete ωjq→ in the crystallographic directions for both optical and acoustical phonon branches. In quasi-harmonic approximation, the theory predicted thermodynamic characteristics (e.g., Debye temperature ΘD(T) and specific heat Cv(T)) for XxY1−xC alloys. Unlike SiC, the GeC, SnC and GexSn1−xC materials have exhibited weak IFCs with low [high] values of ΘD(T) [Cv(T)]. We feel that the latter materials may not be suitable as fuel-cladding layers in nuclear reactors and high-temperature applications. However, the XC and XxY1−xC can still be used to design multi-quantum well or superlattice-based micro-/nano devices for different strategic and civilian application needs
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