Quantitative XPS: Influence of Elastic Electron Scattering in Quantification by Peak Shape Analysis

Abstract

A new method for non-destructive quantitative analysis of surface nanostructures was developed in recent years. It relies on analysis of the XPS peak shape and usually the effects of elastic electron scattering are neglected in practical applications of the method. In the present paper we study the influence of elastic electron scattering for interpretation of the analysed experimental data. Spectra of the Au 4d peak [with inelastic mean free path (IMFP)=16 A] from a thin layer of Au atoms situated at varying depths in a Ni solid were analysed. When elastic scattering is neglected, the accuracy of the quantification is ∽10% for depths smaller than 1.5 IMFP but for a depth of 2.5 IMFP the determined quantitative amount of gold is 25% too low. The effect of elastic scattering on the peak intensity was <10% for marker depths up to 1 IMFP but it grows to ∽40% at 2.5 IMFP. After correction for elastic scattering effects, the accuracy of the analysis is improved and the root-mean-square scatter in the determined amount of Au around the mean value is reduced from 15.4% when elastic scattering effects are neglected to 11% when they are included in the analysis. For the present system, it is then concluded that the effect of elastic scattering is quite small for marker depths smaller than ∽1 IMFP but for larger depths the effect is substantial. © 1997 John Wiley & Sons, Ltd.