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 s pectra recorded using 110 eV photons reveal two components for the 2 r oot 3 phase with the smaller one shifted by 0.38 eV towards low kineti c energy relative to the larger one, The root 3 phase on the other han d could only be fitted with three components. The intensity of the lar gest component decreases with increasing Sn coverage and almost disapp ears at 1.1 monolayers (i.e. corresponding to the 2 root 3 phase). Fro m our analysis, we find that in the root 3 phase, 10% of the surface i s 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) 19 98 Elsevier Science B.V.