Level of consistency in quantification and IMFP determination by the Tougaard method applied to XPS of a Langmuir–Blodgett film taken at widely different emission angles

A photopolymerized cadmium 10,12‐pentacosadiynoate Langmuir–Blodgett (LB) film was transferred onto a silicon wafer substrate with a native oxide layer. The film was investigated by quantitative analysis of peak intensity and peak shape (the Tougaard method). This method has not been applied previously to a series of spectra taken at different emission angles. The objective of this paper is therefore twofold: to determine the ability of this method to give consistent quantification from analysis of spectra from the same sample but taken at widely different emission angles; and to determine the inelastic mean free paths (IMFPs) and compare the values to those determined earlier by angle‐resolved x‐ray photoelectron spectroscopy from the same structures. Survey spectra taken at several emission angles between 5° and 78° were analysed and IMFPs were determined at the energies corresponding to the Cd 3d, O 1s and Si 2s,p photoelectron peaks. It was found that for each core level the spectra taken at all angles ⩽ 73° give consistent quantification to within a standard deviation of 5–10%. This is approximately the same as the uncertainty in quantification made on the basis of a spectrum taken at a single angle. The IMFPs in the LB film are determined to be 29.2 ± 1.7 Å at 955 eV and 40.2 ± 2.2 Å at 1388 eV. These values are close to those obtained in a previous paper and are in good agreement with the reported values for polyethylene calculated from the optical data. Copyright © 2001 John Wiley & Sons, Ltd.