Variable angle XPS investigation of lubricant films coated on sputtered carbon

The thickness t of the fluorocarbon lubricant applied on the sputter‐deposited carbon substrates is measured using the uniform overlayer model\documentclass{article}\pagestyle{empty}\begin{document}$$ t = {\rm \lambda }_{\rm c} {\rm sin \theta In}(aR + 1), $$\end{document} where γ c is the mean free path of the C 1s photoelectrons in the lubricant, R is the experimentally measured intensity ratio of the fluorocarbon to the hydrocarbon components of the C 1s line, θ is the photoelectron take‐off angle, and a is the ratio of C 1s intensity from the lubricant‐free substrate to that from the bulk lubricant. A procedure for experimentally determining the a value, using a partially gold‐coated graphite substrate as a reference, is reported. Values of 4.1, 2.9 and 2.2 were obtained for a respectively on sputter cleaned substrates of graphite, carbon on silicon wafer and carbon on thin film magnetic recording disk. The lower a values of the deposited films are attributed to the presence of voids in the films. Oxidation causes a decrease in a by reducing the carbon content of the substrates, The experimentally determined a values are verifled by monitoring the relative variation in the C 1s and the F 1s signal intensities as a function of θ. The angle dependence of a is discussed.