Metal-semiconductor fluctuations on reconstructed Sn-Si(111) surfaces

We present soft X-ray photoelectron spectroscopy results from the T-4-Sn/Si(111)-(root 3 x root 3)R30 degrees (root 3 for short) and the Sn/Si(111)-(2 root 3 x 2 root 3 R30 degrees (2 root 3 for short), Sn 4d spectra recorded using 110 eV photons reveal two components for the 2 root 3 phase with the smaller one shifted by 0.38 eV towards low kinetic energy relative to the larger one, The root 3 phase on the other hand could only be fitted with three components. The intensity of the largest component decreases with increasing Sn coverage and almost disappears at 1.1 monolayers (i.e. corresponding to the 2 root 3 phase). From our analysis, we find that in the root 3 phase, 10% of the surface is covered by 2 root 3 reconstruction and 90% by root 3 reconstruction. These results suggest metal-semiconductor fluctuations on the root 3 reconstruction as well as for mixed root 3 and 2 root 3 phases. (C) 1998 Elsevier Science B.V.