Scanning tunneling spectroscopy investigation of the (√3 x √3)R30° Sn/Si(111) α and γ surfaces

Scanning tunneling spectroscopy (STS) has been used to investigate the electronic structure of the 1/3 ML Sn1-xSix/ Si(1 1 1) 2D alloy at 300 K for the two limiting cases of x approximate to 0 and x = 0.5 corresponding to the alpha and gamma (or mosaic) phases of the Sn induced (root3 x root3)R30degrees structure. Spectra of the alpha-surface compare well with k(\\) resolved photoemission and inverse photoemission spectra reported in the literature, but less well, in the empty state region, with theoretical band structure calculations. The surface is metallic (or semiconducting with a small gap of order 100 meV) and there are two main structures above and below the Fermi level. STS of the gamma phase also shows metallic (or similar semiconducting) behaviour of the surface, in contrast to the related semiconducting gamma-Pb/Si(1 1 1) and gamma-Pb/Ge(1 1 1) phases. (C) 2004 Elsevier B.V. All rights reserved.