QUANTITATIVE-ANALYSIS BY XPS USING THE MULTILINE APPROACH

An efficient method for quantitative XPS analysis is the so-called multiline approach. This method does not require standards, it takes into account the instrumental and matrix effects and it derives quantitative information from statistical analysis of all photoelectron intensities visible in the spectre. One can expect the reliability of this approach to be better than the reliability of methods involving uncorrected relative sensitivity factors. This paper summarizes recent improvements in the multiline approach. In particular, a new expression for the universal energy dependence of the inelastic mean free path is currently used. Furthermore, the statistical analysis has been modified in order to account properly for the error in the countrates. Finally, a database with physical constants has been added (photoionization cross-sections, asymmetry parameters, binding energies, etc.) to avoid errors of polynomial approximations. The modified algorithm of the multiline approach was applied to photoelectron intensities measured for AuCu alloys in four laboratories. Surfaces of these alloys were sputtered with 2 keV Ar+ ions, because at this energy the selective sputtering effects are expected to be negliible. Very consistent results were obtained. The average deviation from the bulk surface composition was found to be equal to +/- 3.2 at.%. Extensive software implementing the described version of the multiline approach is presently being developed.