Comparison of AES and XPS analysis of thin passive films

Abstract

The surface composition and elemental depth profiles of native oxide films formed on amorphous FeCrNiPB alloys have been studied using both Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS). Although both AES and XPS are surface sensitive techniques, differences in electron escape depths for various Auger and photoelectron peaks result in different sample volumes being analyzed by the two methods. This is found to be significant for specimens that have thin surface films with a varying elemental depth composition such as passive layers. Standard XPS and AES analysis of the data from the surface films using either published or bulk normalized sensitivity factors gave different results for the film composition from the two techniques. In addition, AES and XPS sputter profiles were dissimilar. A ’’true’’ depth profile was constructed using an iterative method, considering escape depth broadening effects and the measured profiles. Model calculations of XPS and AES film compositions based on this profile reproduce the differences observed in the experimental XPS and AES data, showing that it is difficult to determine the content of a complex film without some type of depth analysis.