Total electron yield method in x-ray absorption spectroscopy: A closer look at the saturation/self-absorption effects (abstract)

Abstract

Total electron yield (TEY) is a common method by which photoabsorption cross sections are measured in x-ray absorption spectroscopy (XAS). Since various material parameters are extracted from these XAS spectra, how well TEY spectra mimic the absorption cross section is a major concern. In cases in which the photoabsorption cross sections are large (e.g., at the absorption edge white lines), saturation and self-absorption effects can play a detrimental role, significantly altering the spectral weights in the near-edge region. In this presentation, we show that at the L edges of transition metals (as well as M edges of rare earths), the XAS spectra measured via TEY do not represent the true absorption cross sections. As a case in point, we discuss the ramifications of this saturation/self-absorption effects on the magnetic circular dichroism measurements, which often rely on TEY data. We evaluate the changes in the spectral weights of the near-edge features and determine the resulting errors in the extracted material quantities, i.e., orbital and spin moments, as a function of film thickness and photon incidence angle.