The (111)-(7 x 7) reconstructed surface was studied by using scanning tunnelling microscopy and spectroscopy. Information on the local density of states in an energy band ranging from 2eV below, to 2eV above, the Fermi level was obtained by applying a positive or negative sample bias voltage. The relationship between topographic and spectroscopic information, and the effect of the transmission probability upon the tunnelling current, was considered. It was demonstrated that the data which were obtained under positive and negative stabilization voltages were completely consistent with each other. The occurrence of defects and their relationship to the atomically resolved tunnelling current was analyzed in detail.

T.Berghaus, A.Brodde, H.Neddermeyer, S.Tosch: Surface Science, 1988, 193[1-2], 235-58