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) f ilm was transferred onto a silicon wafer substrate with a native oxide laye r. The film was investigated by quantitative analysis of peak intensity and peak shape (the Tougaard method). This method has not been applied previou sly to a series of spectra taken at different emission angles. The objectiv e of this paper is therefore twofold: to determine the ability of this meth od 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 determin ed earlier by angle-resolved x-ray photoelectron spectroscopy from the same structures. Survey spectra taken at several emission angles between 5 degr ees and 78 degrees were analysed and IMFPs were determined at the energies corresponding to the Cd 3d, O 1s and Si 2s,p photoelectron peaks. It was fo und that for each core level the spectra taken at all angles less than or e qual to 73 degrees give consistent quantification to within a standard devi ation of 5-10%. This is approximately the same as the uncertainty in quanti fication 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 Angstrom at 955 eV and 40 .2 +/- 2.2 Angstrom at 1388 eV. These values are close to those obtained in a previous paper and are in good agreement with the reported values for po lyethylene calculated from the optical data. Copyright (C) 2001 John Wiley & Sons, Ltd.