Thickness of natural oxide films determined by AES and XPS with/without sputtering

Abstract

The thickness of natural air-formed oxides on Al, Si, Fe, Ni, and Ta is determined by Auger electron spectroscopy (AES), depth profiling, and angle-resolved photoelectron spectroscopy (XPS). The sputter rate of the oxides is measured under the same conditions and their values are given with respect to a certified standard 100 nm Ta2O5 reference. Data from AES depth profiling are corrected for the influence of the electron mean free path. XPS data are evaluated from area intensities of the bands after peak synthesis (fitting). Using literature values of mfp for oxides, their thickness is evaluated. AES and XPS data are in reasonable agreement giving oxide thickness ranging from 0.2 to 5 nm increasing in the order of SiO2<NiO<Al2O5<Fe2O3.