The surface film on an oxidized multicomponent alloy usually contains a number of metallic and oxidized phases. During depth-profile analysis, such metal and oxide phases can be differentiated by x-ray photoelectron spectroscopy (XPS), provided the surface oxides are sufficiently stable to withstand ion bombardment without decomposition. A quantitative analysis of the surface composition, however, is not possible without taking account of the effects of preferential sputtering of some phases. We have investigated the effects of 3-keV argon ion bombardment on the composition of oxide-free surfaces of iron–nickel and iron–nickel–chromium alloys. In addition, the effect of ion bombardment on metal–metal oxide surfaces has been studied using composite preparations of metal particles, 10–50 μm diameter, in an oxide matrix. Quantitative XPS measurements of the sputtered alloy surfaces, using photoelectrons of 1.0–2.0 nm mean free path, do not reveal any significant change in the steady-state compositions (i.e., ≳10%) compared with the bulk compositions. In the composite metal–oxide mixtures studied, depletion of the metallic phase is significant in some cases and must be taken into consideration in a quantitative depth profile.

McIntyre, N. S., & Stanchell, F. W. (1979). Preferential sputtering in oxides as metals and revealed by x-ray photoelectron spectroscopy. Journal of Vacuum Science and Technology, 16(2), 798–802.