A theoretical study was made of the geometrical and electronic properties of the C- and Si-terminated β-SiC(001) surfaces in the vicinity of the missing dimer defect. The experimental results suggested that the atomic structures of these 2 surfaces could be considerably modified by external stress. In the present study, the possible influence of this factor upon the surface geometry of both systems was considered. It was shown that the structural differences between the C- and Si-terminated surfaces led to their differing behaviours in the presence of a missing dimer and applied stress. In the case of the C-terminated c(2x2) surface, the missing dimer defect caused the buckling of the adjacent carbon dimers lying in the line of the defect (dimer atoms adjacent to the defect have vertical positions lower by 0.18Å). This effect becomes more pronounced in the presence of compressive stress — the stress of 8% leads to the buckling of these two dimers of around 0.5Å. The vertical positions of silicon atoms located directly below the defect were increased by 0.2Å. It was also found that the missing dimer influenced the structure of the C dimers on the neighbouring lines of dimers. Contrary to the C-terminated surface, the missing dimer defect on the Si-terminated SiC(001)-p(2x1) surface remained neutral for Si dimers located in the line of defect, i.e. the dimers do not change their geometrical properties in unstrained structure nor in the presence of a tensile stress. On the other hand, this defect modifies considerably the geometry of the dimers from the two neighbouring lines of dimers by reducing their bond lengths and vertical positions. Changes in the geometrical properties of the second neighbour dimers (with respect to the defect) in these two lines were also noticeable. Moreover, it was found that the presence of a missing dimer significantly modified the positions of the adjacent sub-surface C atoms.

A Theoretical Study of Structural and Electronic Properties of a Missing Dimer Defect on Si- and C-Terminated SiC(001). B.Pieczyrak, L.Jurczyszyn: Applied Surface Science, 2008, 254[14], 4357-64