Lattice dynamics of SiC polytypes within the bond-charge model

Hofmann, Matthias J.; Zywietz, A.; Karch, K.; Bechstedt, F.

doi:10.1103/physrevb.50.13401

Cited by 104 publications

(64 citation statements)

References 47 publications

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“…The experimental results from Ref. [ 2] support therefore the DOS calculated with the bond charge model by Hofmann et al [ 19].…”

supporting

confidence: 77%

“…Note that the phonon dispersion of the hexagonal polytypes, calculated in Ref. [ 19], exhibits an overbending of the TO branches, which mainly occurs around the K-point of the Brillouin zone. The relatively large value of Γ 2 observed for the TO(0) mode compared to those of Si, Ge and α-Sn (see Table I) provides evidence of a non-vanishing DOS caused by an overbending of the phonon dispersion.…”

mentioning

confidence: 99%

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Disorder-induced phonon self-energy of semiconductors with binary isotopic composition

2002

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Self-energy effects of Raman phonons in isotopically disordered semiconductors are deduced by perturbation theory and compared to experimental data.In contrast to the acoustic frequency region, higher-order terms contribute significantly to the self-energy at optical phonon frequencies. The asymmetric dependence of the self-energy of a binary isotope system m 1−x M x on the concentration of the heavier isotope mass x can be explained by taking into account second-and third-order perturbation terms. For elemental semiconductors, the maximum of the self-energy occurs at concentrations with 0.5 < x < 0.7, depending on the strength of the third-order term. Reasonable approximations are imposed that allow us to derive explicit expressions for the ratio of successive perturbation terms of the real and the imaginary part of the self-energy. This basic theoretical approach is compatible with Raman spectroscopic results on diamond and silicon, with calculations based on the coherent potential approximation, and with theoretical results obtained using ab initio electronic theory. The extension of the formalism to binary compounds, by taking into account the eigenvectors at the individual sublattices, is straightforward. In this manner, we interpret recent experimental results on the disorder-induced broadening of the TO (folded) modes of SiC with a 13 C-enriched carbon sublattice. 1,2

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“…The experimental results from Ref. [ 2] support therefore the DOS calculated with the bond charge model by Hofmann et al [ 19].…”

supporting

confidence: 77%

mentioning

confidence: 99%

Disorder-induced phonon self-energy of semiconductors with binary isotopic composition

2002

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“…The XRD results indicated that 6H±SiC is the major polytype in both SiC-I and SiC-II; the elastic constants (stiness tensor [C ]) for 6H±SiC are reported as follows [75]: …”

Section: A1 Elastic Anisotropymentioning

confidence: 99%

Damage evolution in dynamic deformation of silicon carbide

et al. 2000

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AbstractÐDamage evolution was investigated in silicon carbide by subjecting it to dynamic deformation in (a) a compression Hopkinson±Kolsky bar (compressive stresses of 5 GPa), and (b) high-velocity impact under con®nement (compressive stresses of 19±32 GPa) by a cylindrical (rod) tungsten alloy projectile. Considerable evidence of plastic deformation, as dislocations and stacking faults, was found in the fractured specimens. A polytype transformation was observed through a signi®cant increase in the 6H±SiC phase at compressive stresses higher than 4.5 GPa (in the vicinity of the dynamic compressive failure strength). Profuse dislocation activity was evident in the frontal layer in the specimen recovered from the projectile impact. The formation of this frontal layer is proposed to be related to the high lateral con®ne-ment, imposed by the surrounding material. It is shown that plastic deformation is consistent with an analysis based on a ductility parameter D K C at y pc p ). The microstructural defects and their evolution were found to be dependent on the concentration of boron and aluminum, which were added as sintering aids. Several mechanisms are considered for the initiation of fracture: (a) dilatant cracks induced by mismatch in the eective elastic moduli between two adjacent grains, leading to internal tensile stresses and creating transgranular fracture. Finite element calculations show that high tensile stresses are generated due to elastic compatibility strains; (b) Zener±Stroh cracks nucleated by the piled up dislocations along grain boundaries, and resulting in intergranular fracture; (c) cracks due to existing¯aws connected with grain-boundary phases, voids, etc.; and (d) stress concentrations due to twinning and stacking faults. The high dislocation density observed in the impacted specimen is consistent with existing models of microplasticity. 7

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“…The estimated values of bulk modulus of polycrystalline 3C-SiC range between 225 and 247 GPa [24]. The estimated value of the bulk modulus for polycrystalline 6H-SiC based on experimental values of single crystal elastic constants Cn, C33, and C12 measured by Arlt and Schodder [26], and the estimated value of C13 by Hofmann et al [25] is 273 GPa. It is difficult to calculate margin of errors in these calculated values of bulk moduli for these two polytypes of SiC.…”

Section: Hydrostatic Compressionmentioning

confidence: 89%

“…Thus, estimates of elastic constants of a polycrystalline SiC must be made on some assumption. Hofmann et al [25] used the bond-charge model in conjunction with the measured Raman spectra, infrared absorption, and reflectivity measurements and luminescence studies on 3C, 2H, 4H, 6H, 10H, 15R, and 21R SiC to obtain the elastic constants of various polytypes of SiC. They calculated the values of elastic constants obtained from the limited sound wave velocity measurements, resonance experiments, and optical and phonon measurements.…”

Section: Hydrostatic Compressionmentioning

confidence: 99%

A Survey of Compression Studies on Silicon Carbide (SiC)

Dandekar¹

2002

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Compression of a solid material under plane shock wave propagation/ loading can provide information related to change in density and shear strength with pressure/stress of the material under inertial confinement. The present work surveys and analyzes the existing shock compression and high-pressure data on silicon carbide to provide pertinent information to material modelers and others for use in their work related to this material. It also points out a set of investigations that needs to be carried out to complement the existing data.u Acknowledgments

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Lattice dynamics of SiC polytypes within the bond-charge model

Cited by 104 publications

References 47 publications

Disorder-induced phonon self-energy of semiconductors with binary isotopic composition

Disorder-induced phonon self-energy of semiconductors with binary isotopic composition

Damage evolution in dynamic deformation of silicon carbide

A Survey of Compression Studies on Silicon Carbide (SiC)

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