XPS quantification with universal inelastic electron scattering cross section including intrinsic excitations

In X-ray excited photoelectron emission (XPS), the shape and intensity of photoelectron peaks are strongly affected by extrinsic excitations due to electron transport out of the surface. It is also influenced by intrinsic excitations due to the sudden creation of the static core hole. In order to approximately determine the primary excitation spectrum of the considered transition corrected for both extrinsic and intrinsic excitations, we developed in a previous work [E. Gnacadja, N. Pauly, S. Tougaard, Surf. Interface Anal. 52 (2020) 413] a universal analytical expression for the energy loss cross section including extrinsic and intrinsic excitations. We apply the present universal cross section to test to what extent these primary excitations spectra can be used for XPS quantification based on peak area ratios. The procedure is applied to the study of three sets of polycrystalline alloys (Cu_0.75Au_0.25, Cu_0.50Au_0.50, and Cu_0.25Au_0.75) and to three metal oxides (HfO₂, ZrO₂, and Cu₂O). We show that although the individual peaks are very different from those obtained with the classical universal Tougaard cross section, the determined quantitative compositions are equivalent (but not better). This implies that the relative contribution from intrinsic excitations is roughly the same for all peaks for a given sample and they therefore cancel out when peak area ratios are considered.