Relaxation of 6H-SiC (0001) Surface and Si Adsorption on 6H-SiC (0001): an ab initio Study

First-principles calculations are carried out to study the relaxation of 6H-SiC (0001) surface and chemisorption models of Si adatoms on four high-symmetry adsorption sites. The surface results show that Si-termination is the preferred termination of the 6H-SiC(0001) polar surface and is more stable than the C-terminated 6H-SiC(0001) polar surface over a wide range of allowed chemical potentials. Four stable atomic configurations (top, bridge, hcp and fcc) are considered, and the adsorption energies and geometries, Mulliken charge population, and partial density of state (PDOS) properties are analyzed. Adsorption energy results show that the top site is the most stable site. The structural properties of Si adsorption on the SiC (0001) surface shows that increasing stability means decreasing bond lengths. Charge populations analysis and PDOS results imply that there is strong interaction between Si adatoms and 6H-SiC (0001) surface.