Validity of Film-Thickness Estimates Based on Angle-Resolved X-ray Photoelectron Spectroscopy Using Various Inelastic Mean-Free-Path Formulae

Abstract

We investigated the thickness of Ag on a W(001) substrate and the native oxide on top of a $\rm Si_{0.8}Ge_{0.2}$ alloy grown on Si(100) substrate. We used X-ray photoelectron spectroscopy to confirm the consistency of various inelastic mean-free-path formulae. Because the Ag/W(001) system is composed of four core levels (W 4$\it f$, W 4$\it d$, Ag 3$\it d$ and Ag 3$\it p_{\rm 3/2}$) and the $\rm O_2$/$\rm Si_{0.8}Ge_{0.2}$ on Si(100) system is composed of three core levels (Si 2$\it p$, Ge 2$\it p_{\rm 3/2}$ and Ge 3$\it d$), these systems are quite useful for checking the accuracy of various inelastic mean-free-path(IMFP) formulae with a variety of combinations between films and substrates. We found that the reported inelastic mean-free-path formulae were uncorrelated in our systems.