Quantitative XPS I. Analysis of X-ray photoelectron intensities from elemental data in a digital photoelectron database

An analysis of the correlation of theoretical predictions for photoelectron intensities is made with experimental data from an XPS digital database for 46 solid elements measured using a spectrometer with calibrated intensity and energy scales. This analysis covers single element samples measured for Al and Mg K alpha X-rays. The spectral data are for widescans at 1 eV energy intervals with kinetic energies from 200 to 1506 eV using Al X-rays and to 1273 eV using Mg X-rays. In addition are narrow scans around the photoelectron peaks at 0.1 eV energy intervals. All spectra have the instrument intensity/energy response function removed so that the peak areas are proportional to the number of electrons emitted per steradian per incident Ka photon. Correlations are made for the ionisation cross sections of Scofield and the inelastic mean free paths given by the TPP-2M formula. The correlations are excellent, apart from a factor which may be associated with the background removal arising from the use of the Tougaard Universal cross section. These correlations lead directly to pure element relative sensitivity factors suitable for quantitative analysis. General equations are also provided to extract values for a new form of relative sensitivity factor for an average matrix. These average matrix relative sensitivity factors lead to simpler equations involving matrix factors that are effectively unity instead of the traditional values in the range 0.3 to 3.0. (C) 2001 NPL. Published by Elsevier Science BY. All rights reserved.