Core-level photoelectron spectroscopy study of the Au/Si(111) 5X2, alpha-root 3X root 3, beta-root 3X root 3, and 6X6 surfaces

Submonolayer coverages of Au on Si(111), known as the 5 X 2, alpha- root3 X root3, beta- root3 X root3, 2root21 X 2root21, and 6 X 6 surfaces, have been investigated by low-energy electron diffraction and photoelectron spectroscopy. Three Si 2p surface components on the 5 X 2 surface, and four surface components on the alpha- root3 X root3, quenched beta- root3 X root3, and 6 X 6 surfaces have been identified by surface sensitive high resolution core-level spectroscopy. The photoemission data of the alpha- root3 X root3, the 6 X 6 and the quenched beta- root3 X root3 phases are discussed in terms of extra Au adatoms on the root3 X root3 surface described by the ideal 1 ML conjugate honeycomb chained trimer model. The similarity between the 6 X 6 and the quenched beta- root3 X root3 surface is obvious from the decomposition of the Si 2p spectra, suggesting an order-disorder relation.