ION BOMBARDMENT-INDUCED CHANGES IN OXIDE-METAL INTERACTIONS STUDIED BY PHOTOELECTRON-SPECTROSCOPY

We have studied the influence of ion bombardment on the surfaces of Mg O and Al2O3 single crystals. The two oxides were sputtered with low en ergy Ar+ ions, and x-ray photoelectron spectroscopy was used to analyz e surface compositions and chemical interactions with metallic adsorba tes. Expected changes in surface compositions have been calculated mat hematically using first principle formulation from existing literature . The resulting effects on XPS spectra have been predicted based on co ncentration profile models and agree with experimental observations. C hanges in surface oxygen activity were studied by evaporating Ni on th ese surfaces at an extremely slow rate and analyzing what fraction of the first monolayer was oxidized on adsorption. This fraction, used as a measure of surface oxygen activity, was substantially reduced in Al 2O3 on sputtering, but remained practically unchanged for MgO. The amo unt of these changes matches reasonably well with calculated changes i n surface oxygen fraction. Based on these results, the relation betwee n ion bombardment and interfacial bonding has been discussed.