Structural and electronic properties of cubic, 2H, 4H, and 6HSiC

Park, C. H.; Cheong, Byoung‐Ho; Lee, Keun-Ho; Chang, Kee Joo

doi:10.1103/physrevb.49.4485

Cited by 340 publications

(233 citation statements)

References 38 publications

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“…Park et al 23 performed ab initio pseudopotential calculations within the local-density approximation for 3C-, 6H-, and 4H-SiC. In accordance with our experimental results the computed VB DOS of the various polytypes shows a strong similarity, while the unoccupied DOS varies with the polytypes.…”

Section: Unoccupied Lpdos Of Sic Polytypessupporting

confidence: 67%

Electronic structure of silicon carbide polytypes studied by soft x-ray spectroscopy

et al. 1999

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The electronic structure of SiC polytypes is investigated with soft x-ray absorption ͑SXA͒ and emission ͑SXE͒ spectroscopy studying the local C p and Si (sϩd) partial density of states ͑LPDOS͒ of n-doped cubic 3C-SiC and hexagonal 4H-and 6H-SiC. The shape and the energetic position of the occupied LPDOS of the valence band measured by nonresonantly excited SXE spectroscopy is nearly identical for the three polytypes, reflecting the local identity of the crystalline structures. The variation of the band gap from 2.2 eV for 3C-SiC to 3.0 eV for 6H-SiC, and 3.3 eV for 4H-SiC is caused by changes of the conduction band alone as reflected by the unoccupied LPDOS measured by SXA. Additionally, by resonantly excited SXE information on the band dispersion and the local symmetry character of the valence states is obtained. ͓S0163-1829͑99͒09715-5͔

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Section: Unoccupied Lpdos Of Sic Polytypessupporting

confidence: 67%

Electronic structure of silicon carbide polytypes studied by soft x-ray spectroscopy

et al. 1999

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“…45 As the unit cell length of wurtzite along the ͓0001͔ axis is double with respect to the zinc blende along the ͓111͔, the phonon dispersion can be approximated by folding the one for the zinc-blende structure along the ͓111͔ direction ͑⌫ → L͒. This operation is represented schematically in Fig.…”

Section: ͑2͒mentioning

confidence: 99%

Raman spectroscopy of wurtzite and zinc-blende GaAs nanowires: Polarization dependence, selection rules, and strain effects

et al. 2009

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Polarization-dependent Raman scattering experiments realized on single GaAs nanowires with different percentages of zinc-blende and wurtzite structure are presented. The selection rules for the special case of nanowires are found and discussed. In the case of zinc-blende, the transversal optical mode E 1 ͑TO͒ at 267 cm −1 exhibits the highest intensity when the incident and analyzed polarization are parallel to the nanowire axis. This is a consequence of the nanowire geometry and dielectric mismatch with the environment, and in quite good agreement with the Raman selection rules. We also find a consistent splitting of 1 cm −1 of the E 1 ͑TO͒. The transversal optical mode related to the wurtzite structure, E 2 H , is measured between 254 and 256 cm −1 , depending on the wurtzite content. The azimuthal dependence of E 2 H indicates that the mode is excited with the highest efficiency when the incident and analyzed polarization are perpendicular to the nanowire axis, in agreement with the selection rules. The presence of strain between wurtzite and zinc-blende is analyzed by the relative shift of the E 1 ͑TO͒ and E 2 H modes. Finally, the influence of the surface roughness in the intensity of the longitudinal optical mode on ͕110͖ facets is presented.

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“…Under this definition, H wurtzite =100% and H diamond = 0% [1,3]. The key consequence of this defi nition is to regard irregular stacking sequences in Si as new phases rather than defects.…”

Section: Ramsdell Notationmentioning

confidence: 99%

“…We next defi ne hexagonality as the percentage of the h layers in a crystal: (1) where N h refers to the total number of hexagonal WZ Si under ambient conditions are scarce [4 6]. Despite the rareness of WZ Si, Sánchez Dehesa argued that the total energy difference between the two polymorphs (diamond and WZ) of Si is insignificant; instead, the likely reason responsible for the stability of the diamond polymorph is the electrostatic energy [7].…”

Section: Dependence Of Cohesive Energy On Hexagonalitymentioning

confidence: 99%

Kinetically-induced hexagonality in chemically grown silicon nanowires

Liu

Wang

2009

Nano Res.

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Various silicon crystal structures with different atomic arrangements from that of diamond have been observed in chemically synthesized nanowires. The structures are typified by mixed stacking mismatches of closely packed Si dimers. Instead of viewing them as defects, we defi ne the concept of hexagonality and describe these structures as Si polymorphs. The small transverse dimensions of a nanowire make this approach meaningful. Unique among the polymorphs are cubic symmetry diamond and hexagonal symmetry wurtzite structures. Electron diffraction studies conducted with Au as an internal reference unambiguously confi rm the existence of the hexagonal symmetry Si nanowires.Cohesive energy calculations suggest that the wurtzite polymorph is the least stable and the diamond polymorph is the most stable. Cohesive energies of intermediate polymorphs follow a linear trend with respect to their structural hexagonality. We identify the driving force in the polymorph formations as the growth kinetics. Fast longitudinal elongation during the growth freezes stacking mismatches and thus leads to a variety of Si polymorphs. The results are expected to shed new light on the importance of growth kinetics in nanomaterial syntheses and may open up ways to produce structures that are uncommon in bulk materials.

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Structural and electronic properties of cubic, 2H, 4H, and 6HSiC

Cited by 340 publications

References 38 publications

Electronic structure of silicon carbide polytypes studied by soft x-ray spectroscopy

Electronic structure of silicon carbide polytypes studied by soft x-ray spectroscopy

Raman spectroscopy of wurtzite and zinc-blende GaAs nanowires: Polarization dependence, selection rules, and strain effects

Kinetically-induced hexagonality in chemically grown silicon nanowires

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