Comparison of source functions obtained by using QUASES and partial intensity analysis for inelastic background correction: KLL Auger spectra of 3d transition elements Cu and Ni

Abstract

AbstractCorrection of photoelectron and Auger spectra excited from solids for the effect of electron scattering is a key problem in quantitative surface analytical applications of XPS and AES. Based on analysis of the spectral shape of the background caused by scattering of the signal electrons, powerful methods have been developed recently and applied successfully for obtaining the ‘source functions’ (i.e. the background‐corrected spectra) as well as the in‐depth concentration profile from the measured spectra.The QUASES analysis has been proposed as a general tool for quantification in XPS, probing depths up to ∼10 inelastic electron mean free paths (λ) using Tougaard's ‘universal’ cross‐section for inelastic scattering and the λ(E) values recommended by Powell and Jablonski. Effects of elastic scattering and surface excitations are neglected with this approach and intrinsic excitations are considered a part of the source function.In the partial intensity approach, the observed spectrum can be decomposed into its constituent parts, i.e. the source function as well as contributions due to intrinsic bulk losses and surface extrinsic losses. This is achieved for an arbitrary emission mechanism. In particular, elastic scattering and different scattering mechanisms at different depths can be accounted for simply and consistently.Both methods have been applied for background correction of KLL Auger spectra of the 3d transition metals Cu and Ni excited by photons from metallic thin films vacuum‐evaporated onto Si substrates. The respective source functions obtained are very similar, especially in the case of thinner films, indicating that elastic scattering and surface effects play only a minor role in influencing the spectral shape at these high energies. A detailed analysis of the differences is given, focusing on the contributions from intrinsic excitations. Copyright © 2002 John Wiley & Sons, Ltd.