PHOTOEMISSION-STUDY OF THE SI(111)-SQUARE-ROOT 3 X SQUARE-ROOT 3-PB MOSAIC PHASE - OBSERVATION OF A LARGE CHARGE-TRANSFER

The Pb-induced square-root 3 x square-root 3 mosaic phase of the Si(111) surface has been studied with Si 2p core-level and angle-resolved photoelectron spectroscopy. The results from these measurements provide evidence for a model with a 1:1 mixture of Pb and Si adatoms for the square-root 3 x square-root 3 mosaic phase, which was proposed in a recent scanning tunneling microscopy study. We observe quite large surface core-level shifts which are interpreted as due to a charge transfer between the different adatom dangling-bond orbitals.