Au / Si ( l l l ) and the Formation of Silicides at the Interface Examined by Spin - Resolved Photoemission

Au on Si(111) in the 1 x 1 structure for different coverages and in the ~/3 x ~/3R30 °, and the 5 x 1 reconstructions has been studied by means of spin-, angle-, and energy-resolved photoemission. The photoemission studies were performed at normal incidence of the circularly polarized light and normal electron emission. In addition to Auand Si-derived peaks other highly spin-polarized peaks are observed for a coverage of 8 Au layers grown at room temperature. In keeping with previous work these peaks are interpreted as silicide peaks. The spin polarization of these peaks gives clues concerning the levels involved in the silicide formation. For a coverage of 16 Au layers on Si(111) in the 1 x 1 structure the photoemission spectra are similar to the spectra of a Au(111) crystal, but also show a contribution of the silicide peaks. For lower coverages the spectra are nearly independent of the structure (1 x 1, ]/~ x V~R30 ° or 5 x 1) and already show peaks other than the pure Auand Si-derived peaks. The Auger signal, however, does not show contributions in addition to the pure Si signal.