STM study of the charged defects on the Ge(111)-c(2 x 8) surface and the effect of density of states on defect-induced perturbation

Defects present on the Ge(111)-c(2 X 8) surface and an effect of surface el ectronic states on the defect-induced perturbation have been studied by sca nning tunneling microscopy (STM). The defects exhibit voltage-dependent cha racteristics in the image. In particular, the empty-state images with low b ias voltages exhibit delocalized brightness variation around the defects, s uggesting that these defects are charged relative to the clean, unperturbed surface. The voltage-dependent but nonmonotonic amplitude of the delocaliz ed brightness in the STM image is explained in relation to the surface elec tronic structure of Ge(111)-c(2 X 8) and the tunneling probabilities. (C) 2 000 Elsevier Science B.V. All rights reserved.