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

Defects present on the Ge 111.-c 2=8. surface and an effect of surface electronic states on the defect-induced perturbation have been studied by scanning tunneling microscopy STM.. The defects exhibit voltage-dependent characteristics in the image. In particular, the empty-state images with low bias voltages exhibit delocalized brightness variation around the defects, suggesting that these defects are charged relative to the clean, unperturbed surface. The voltage-dependent but nonmonotonic amplitude of the delocalized brightness in the STM image is explained in relation to the surface electronic structure of Ge 111.-c 2=8.and the tunneling probabilities. q2000 Elsevier Science B.V. All rights reserved.