Imaging charged defects on clean Si(100)-(2x1) with scanning tunneling microscopy

Scanning tunneling microscopy (STM) has been used to image charged defects on the clean Si(100)-(2x1) surface. Previous studies have shown that, in the absence of C-type defects, the surface does not pin the Fermi level, allowing near surface charge to influence the state density contributing to the tunneling current. As in the case of cleavage faces of III-V semiconductor crystals, the charge-induced band bending produces long-range enhancements superimposed on the periodic surface lattice. This is observed in empty-state STM images taken on n-type material. No band bending signature is seen in the filled-state images. This can be understood by considering the band structure at the surface, which has surface states within the band gap. The charged defects observed in this work are of the types commonly observed in clean Si(100)-(2x1) STM studies, however, not all defects of a given type appear charged. This would indicate subtle differences in structure or the influence of impurities. Predictions for p-type material will also be made. (C) 2002 American Institute of Physics.