The electronic effects of 2 well-defined defects were studied by using scanning tunnelling microscopy. It was found that an atomic vacancy on the uppermost (00•1) plane led to a decrease in the apparent z-height, over a 3nm x 3nm area, of about 0.15nm. Plane rotation relative to the third surface layer produced a Moiré pattern with an attenuation along the c-axis of about 2.6 per monolayer. A so-called super-vacancy was seen, due to competition between these 2 effects. The results were explained in terms of a change in the density of states near to the Fermi level.

Z.Y.Rong: Physical Review B, 1994, 50[3], 1839-43