Standard Approaches to XPS and AES Quantification—A Summary of ISO 18118:2024 on the Use of Relative Sensitivity Factors

Quantitative analysis of electron spectroscopy data from techniques such as Auger electron spectroscopy (AES) and X‐ray photoelectron spectroscopy (XPS) typically requires the use of relative sensitivity factors (RSFs). Virtually, all routine XPS experiments attempt to turn peak intensities into elemental or chemical compositions using RSFs. The comparability and reproducibility of surface chemical analysis by electron spectroscopies therefore require the standardisation of RSFs and their use. RSFs may be determined either from theoretical calculations based on photo‐ionisation cross‐sections or empirically through direct measurement of homogeneous reference samples of known composition. The accurate use of sensitivity factors, even empirically determined RSFs, requires accounting for the effect of material differences on relative intensities, the so‐called ‘matrix effects’. ISO 18118:2024 is the most recently revised version of the ISO standard for the use and determination of empirical RSFs for quantitative analysis of homogeneous materials by AES and XPS. This article provides a summary of the new, updated standard and the methods described therein, noting in particular the revisions made since the previous edition, ISO 18118:2015.