Photoemission investigation on the oxidation of Si(111)Ag interfaces and its relation to the interface structure

We give the first photoemission results on the enhancement of Si reactivity to oxygen when a noble metal (Ag) is present. The tunability of synchrotron radiation (SR) has been used to get high surface sensitivity and to take advantage of cross section energy dependence. We show that when one monolayer of Ag is deposited onto Si(111), the exposure to oxygen (30 × 106L) originates the overgrowth of an oxide phase which is basically SiO2. This indicates that Ag breaks the sp3configuration of Si atoms with a consequent dramatic increase in the Si reactivity. This behaviour rules out the model of Ag adsorbed on top of Si with an atomically abrupt interface.