A theoretical study of the atomic and electronic structure of a grain boundary in cubic SiC

Abstract

The atomic and electronic structure of the (122) Sigma =9 grain boundary in cubic SiC has been calculated for the first time using the self-consistent tight-binding (SCTB) method. An atomic model consisting of a zig-zag arrangement of five-membered and seven-membered rings similar to that in the same boundary in Si or Ge has been constructed from a high-resolution electron microscope image, although Si-Si and C-C wrong bonds are repeated alternately at the interface in this model. The authors have also performed calculations of the same boundary in Si using the SCTB method for comparison, and have obtained results similar to those previously obtained by other theoretical schemes. The calculated boundary energy in SiC has shown that the present atomic model can exist stably compared with the two surfaces, and the calculated boundary electronic structure in SiC has no deep states in the gap as well as that in Si. These results indicate the possibility that stable boundary structures can be constructed by arranging structural units in SiC as well as in covalent semiconductors. However, it has been found that the presence of the wrong bonds greatly influences the boundary energy and the boundary electronic structure.