COADSORPTION AND REACTION OF SULFUR AND SILVER ON A RU(001) SURFACE

We have investigated the interaction of Ag and S coadsorbed on a Ru(00 1) surface using high-resolution soft X-ray photoemission spectroscopy of the S 2p core level and valence region. The interaction of adsorbe d sulfur and the first layer of Ag adatoms is weak. Theta(S)+Theta(Ag) <0.5 ML, Ag and S are coadsorbed in segregated domains. The Ag layer i s covered by chemisorbed S only after a S-saturation of the Ru surface (Theta(S)>0.5 ML). At Ag coverages higher than one monolayer, the val ence band and the S 2p spectra show formation of Silver sulfide at roo m temperature.