First-Principles Study on Electronic Structure of 15R-SiC Polytypes

Zhang, Fu Chun; Gao, Ying; Cui, Hong; Ruan, Xing Xiang; Zhang, Wei Hu

doi:10.4028/www.scientific.net/amr.971-973.77

Cited by 3 publications

(4 citation statements)

References 14 publications

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“…The high content of Fe and V impurities in β‐SiC powders (Table 1) resulted in the donor–acceptor compensation and trapping of charge carriers, 30 which is also indicated by an increase in carrier density from 1.1 × 10 10 to 2.8 × 10 13 cm −3 with increasing initial α‐phase content (Figure 3). The bandgap energies of 6H, 15R, and 4H, are 3.10, 2.98, and 3.29 eV, respectively 31,32 . Various metallic and nonmetallic impurities are known to affect the electrical properties of SiC ceramics 30,33 .…”

Section: Resultsmentioning

confidence: 99%

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Effects of initial α‐phase content on properties of pressureless solid‐state sintered SiC ceramics

Malik

Kim

2021

Int J Applied Ceramic Tech

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α‐ and β‐SiC starting powders of similar particle sizes were used to investigate the effect of initial α‐phase content on the electrical, thermal, and mechanical properties of pressureless solid‐state sintered (PSS) SiC ceramics with B4C and C additives. For β‐SiC starting powders, a coarse‐grained microstructure with elongated platelet grains was formed by the transformation of 3C to 6H and finally to 4H‐SiC phase. In contrast, materials prepared from α‐SiC powders exhibited a fine‐grained microstructure with platelet grains. This study revealed the beneficial effect of α‐SiC starting powders in achieving low electrical resistivity and high thermal conductivity in PSS SiC ceramics, which was attributable to their higher sinterability, lower impurity content, and lower 6H to 4H‐SiC phase transformation rate compared with β‐SiC powders. The electrical resistivity decreased by an order of magnitude and the thermal conductivity increased by 32% with an increase in initial α‐phase content from 0 to 100%. The flexural strength increased by approximately 16% with increasing initial α‐phase content due to a decreased flaw size with decreasing grain size. However, the fracture toughness and hardness were insensitive to the change in initial α‐phase content.

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Section: Resultsmentioning

confidence: 99%

“…The bandgap energies of 6H, 15R, and 4H, are 3.10, 2.98, and 3.29 eV, respectively. 31,32 Various metallic and nonmetallic impurities are known to affect the electrical properties of SiC ceramics. 30,33 Impurities like Al, B, Ga, and Sc are p-type dopants, whereas N, P, and Fe are n-type dopants.…”

Section: Electrical and Thermal Propertiesmentioning

confidence: 99%

Effects of initial α‐phase content on properties of pressureless solid‐state sintered SiC ceramics

Malik

Kim

2021

Int J Applied Ceramic Tech

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“…3). The bandgap energies of 6H, 15R, and 4H, are 3.10, 2.98, and 3.29 eV, respectively [49,50]. Various metallic and non-metallic impurities are known to affect the electrical properties of SiC ceramics [48,51].…”

Section: Electrical and Thermal Propertiesmentioning

confidence: 99%

Effects of initial α-phase content on the electrical, thermal, and mechanical properties of pressureless solid-state sintered SiC ceramics

Malik¹,

Kim²

2021

Preprint

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αand β-SiC starting powders of similar particle sizes were used to investigate the effect of initial α-phase content on the electrical, thermal, and mechanical properties of pressureless solid-state sintered (PSS) SiC ceramics with B4C and C. For β-SiC starting powders, a coarse-grained microstructure with elongated platelet grains formed by the 3C to 6H to 4H-SiC phase transformation was obtained. In contrast, α-SiC powders exhibited a fine-grained microstructure with platelet grains. The electrical resistivity decreased by an order of magnitude with increasing initial α-phase content presumably due to (1) an increased 6H-SiC content causing a decrease in bandgap energy and (2) the low soluble impurity content (Fe and V) of the α-SiC powders. The thermal conductivity increased by approximately 32% with increasing initial α-phase content due to (1) an increased 6H-SiC content, which has a higher intrinsic thermal conductivity compared to 4H and (2) the low impurity content of the α-SiC powders. The flexural strength increased by approximately 16% with increasing initial α-phase content due to a decreased flaw size with decreasing grain size. However, the fracture toughness and hardness were insensitive to the change in initial α-phase content.

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“…In discussing our model below we will see that the structure of the Nb-related spectrum stems from the structure of the valence band, which is similar in the hexagonal 4H and 6H SiC polytypes and it is sufficient to investigate in detail one of them. On the other hand, although there exist both experimental [21] and theoretical [22] studies on the valence-band structure of 15R SiC, the rhombohedral 15R polytype is substantially less explored than the hexagonal polytypes. Therefore, in the rest of this paper we shall consider in detail only the 4H-SiC polytype.…”

Section: B Temperature Dependence and Ple Spectroscopymentioning

confidence: 99%

Optical properties and Zeeman spectroscopy of niobium in silicon carbide

et al. 2015

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The optical signature of niobium in the low-temperature photoluminescence spectra of three common polytypes of SiC (4H, 6H, and 15R) is observed and confirms the previously suggested concept that Nb occupies preferably the Si-C divacancy with both Si and C at hexagonal sites. Using this concept we propose a model considering a Nb-bound exciton, the recombination of which is responsible for the observed luminescence. The exciton energy is estimated using first-principles calculation and the result is in very good agreement with the experimentally observed photon energy in 4H SiC at low temperature. The appearance of six Nb-related lines in the spectra of the hexagonal 4H and 6H polytypes at higher temperatures is tentatively explained on the grounds of the proposed model and the concept that the Nb center can exist in both C 1h and C 3v symmetries. The Zeeman splitting of the photoluminescence lines is also recorded in two different experimental geometries and the results are compared with theory based on phenomenological Hamiltonians. Our results show that Nb occupying the divacancy at the hexagonal site in the studied SiC polytypes behaves like a deep acceptor.

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First-Principles Study on Electronic Structure of 15R-SiC Polytypes

Cited by 3 publications

References 14 publications

Effects of initial α‐phase content on properties of pressureless solid‐state sintered SiC ceramics

Effects of initial α‐phase content on properties of pressureless solid‐state sintered SiC ceramics

Effects of initial α-phase content on the electrical, thermal, and mechanical properties of pressureless solid-state sintered SiC ceramics

Optical properties and Zeeman spectroscopy of niobium in silicon carbide

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