Variable angle x-ray photoelectron spectroscopy and ion scattering spectroscopy study of the Ag/SiO2 interface

Abstract

Thin Ag films of up to one monolayer on high purity fused silica have been investigated using variable angle x-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS). Silvered samples were prepared using the wet chemical process without reducers or by vacuum evaporation. After sensitization with a tin complex, it was determined from ISS that Sn is a surface species only and covers up to 30% of Si surface sites. Variable angle XPS verified these findings and suggested that the Sn is located above the Si surface plane. After silvering with the wet chemical process so that less than a monolayer of Ag is present on the surface, XPS showed that up to 60% of the surface Si is bound to Ag, while 20% of the surface Si sites remain covered by a Sn complex. ISS verified that Ag is a surface species and that 80% of the surface is covered by Ag and Sn. Variable angle XPS showed that Ag is raised out of the surface plane, and that it probably also resides over the Si. Analysis of one monolayer Ag films formed by vacuum evaporation on SiO2 show similar results. Using XPS peak positions and Auger parameter shifts, evidence was found for Ag–Si bonding. Variable angle ISS gave strong evidence of Ag residing over the Si.