Tunnelling spectroscopy and voltage-dependent scanning tunnelling microscopy were used to study the geometry and electronic properties of atomic-sized defects on the (001) surface. Individual dimer vacancies were shown to be semiconducting, and to support the p-bonded defect model. Another type of characteristic defect gave rise to strong metallic tunnelling. This indicated that it had a high density of states at the Fermi level and was likely to be active in Fermi pinning on (001). Spatially-dependent I-V measurements and tunnelling barrier height determinations directly revealed the spatial extent of the metallic character and indicated the effective size of the defects.

R.J.Hamers, U.K.Köhler: Journal of Vacuum Science and Technology A, 1989, 7[4], 2854-9