Scanning tunneling microscopy was used to image charged defects on the clean Si(100)-(2 x 1) 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 produced long-range enhancements superposed on the periodic surface lattice. This was observed in empty-state scanning tunnelling microscopic images taken on n-type material. No band bending signature was seen in the filled-state images. This could be understood by considering the band structure at the surface, which has surface states within the band gap. The charged defects observed here were of the types commonly observed in clean Si(100)-(2 x 1) scanning tunnelling microscopic studies, however, not all defects of a given type appeared charged. This would indicate subtle differences in structure or the influence of impurities.

Imaging Charged Defects on Clean Si(100)-(2 x 1) with Scanning Tunneling Microscopy. G.W.Brown, H.Grube, M.E.Hawley, S.R.Schofield, N.J.Curson, M.Y.Simmons, R.G.Clark: Journal of Applied Physics, 2002, 92[2], 820-4