Results show that the zero-phonon line of the defect gradually converges as the supercell increases. Electrical properties of carbon vacancy defects in 4H-SiC supercellsįigure 7 shows a comparison of the zero-phonon line energy of the defects under different supercells. The comparison shows that the HSE06 functional is more accurate than the PBE functional in describing the energy band structure of 4H-SiC. 27 The valence band maximum of the 4H-SiC energy band diagram is at Γ point, and the conduction band minimum (CBM) is at M point, which is an indirect band gap semiconductor. The result is similar to the 3.19 eV calculated by Yan et al. In addition, the band gap of the 4H-SiC unit cell is 3.18 eV, which is close to the experimental result of 3.26 eV with a difference of about 2.4%. The energy band result using the HSE06 functional obtained is shown in Fig. 26 This discrepancy can be ascribed to the fact that the PBE functional underestimates the correlation between excited state electrons, which explains the low calculation result of the energy band. ![]() The 4H-SiC band gap width is 2.63 eV, which is different from the experimental result of 3.26 eV but is similar to the calculated result of Cheng et al. The calculation of formation energy shows that the most stable carbon vacancy defects in the material are V C 2+(k), V C +(k), V C(k), V C −(k) and V C 2−(k) as the electronic chemical potential increases.įigure 5(a) shows the energy band structure calculated using the PBE exchange-correlation functional method. Comparison of the calculated hyperfine tensor with the experimental results indicates the existence of carbon vacancies in SiC lattice. The hyperfine tensors of V C +(h) and V C +(k) were calculated. Results show that the zero-phonon line energies of carbon vacancy defects are much lower than those of divacancy defects, indicating that the former is more likely to reach the excited state than the latter. ![]() The zero-phonon line energies, hyperfine tensors, and formation energies of carbon vacancies with different charge states (2 −, −, 0, + and 2 +) in different supercells (72, 128, 400 and 576 atoms) were calculated using standard Perdew–Burke–Ernzerhof and Heyd–Scuseria–Ernzerhof methods. In this study, density functional theory was used to characterize the carbon vacancy defects in hexagonal (h) and cubic (k) lattice sites. Thus, understanding the properties of this defect is critical to its application, and the atomic and electronic structures of the defects needs to be identified. Carbon vacancy is a dominant defect in 4H-SiC. As a promising material for quantum technology, silicon carbide (SiC) has attracted great interest in materials science.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |