A simple approach to the polytypism in SiC

Abstract

A simple approach to the polytypism in SiC is proposed on the basis of phenomenological energy formula incorporating electrostatic interactions between interatomic bond charges and between ionic charges. The versatility of our approach is confirmed by calculating the energy differences among 3C (zinc blende), 6H, 4H and 2H (wurtzite) structures with/without vacancy. When the ionicity fi=0.232 for SiC is employed, the calculated respective energy differences ΔE for 6H, 4H, and 2H are very small such as 0.18meV/atom, 0.27meV/atom, and 5.7meV/atom where the energy origin is the energy for the most stable 3C. Furthermore, it is found that vacancy formation stabilizes 4H– or 6H–SiC. This is because the vacancy formation reduces the interatomic bond charges to destabilize 3C–SiC. These results are consistent with our previous ab initio calculations and experimental findings where 3C appears at low temperatures while 6H and 4H for SiC are favored at high temperatures enhancing vacancy formation. Our simple approach is also applied to the polytypism in SiC with impurities.