Surface characterization study of AgF and AgF 2 powders using XPS and ISS

Abstract

XPS and ISS data have been collected from pressed AgF and AgF 2 powder samples obtained from AESAR. The samples were sputter-cleaned in vacuum for 10 min with 1 keV He + to reduce the amounts of surface contaminants present. Negative shifts in XPS BEs and increased peak widths are observed with increasing silver oxidation state for the Ag 3d peaks according to the XPS data. This negative BE shift with increasing oxidation state is opposite to that expected based on simple charge-transfer arguments. Significant negative KE shifts between the Auger features are obtained from Ag metal, AgF, and AgF 2 similar to those observed for Ag metal, Ag 2O and AgO. The XPS F 1s and F 2s peaks indicate the presence of multiple chemical states of fluorine including fluoro-hydrocarbon and/or-alcohol-like species in addition to fluorides. As prepared AgF and AgF 2 samples were found to have F Ag ratios of 0.60 and 1.75, respectively. Since the stoichiometries of AgF and AgF 2 predict F Ag ratios of 1.00 and 2.00, respectively, the excess Ag is present in chemical forms other than the silver-halide. Both samples contain mixed chemical states of Ag 0, Ag + and Ag 2+. The primary contaminants consist of O and C. Multiple chemical states of O are present on the outermost and near-surface regions of the as-prepared samples including atomically adsorbed oxygen, carbonates, absorbed water, hydroxyl groups and various oxygen-containing carbon compounds. The XPS C 1s peak shapes are quite complex with features due to the presence of several different carbon species including carbide, hydrocarbons, alcohols, carbonate, CHF and CFO(OH)-like species.