Accuracy of the non‐destructive surface nanostructure quantification technique based on analysis of the XPS or AES peak shape

Abstract

The accuracy of XPS and AES quantification by peak shape analysis was established from a detailed analysis of a range of model spectra and three sets of experiments. It was found that information on the concentration–depth profile in the surface region up to depths of ∽5λi (where λi is the inelastic electron mean free path) is primarily contained in the spectral energy region up to ∽100 eV below the peak energy and is essentially completely contained by the energy region up to ∽200 eV below the peak. Analysis of a larger energy range than 100 eV does not add much to the information on the details of the structure in the outermost 5λi but gives the possibility to determine additional structural parameters that describe the composition at larger depths. The structural parameters that describe the chemical composition of the outermost 5–10λi of the solid were divided into primary and secondary parameters: the primary parameters are the three most important parameters needed to describe the main characteristics of the distribution of atoms; the secondary parameters are parameters other than the three primary parameters that describe the finer details of the depth distribution of atoms in the outermost 5–10λi of the surface region. The uncertainty in the determined three primary parameters is typically 5–10%. The uncertainty in the determined secondary parameters is typically ≳35%. Different models of depth profiles can be distinguished when they differ significantly over a width of more than ∽1/3λi at any depth ≲5λi. The uncertainty in the total determined amounts of atoms within the surface region is ∽5–10% as long as the depths are within the primary probing depth of the method (i.e. <5λi). The absolute quantification of a set of samples where the in-depth distribution varies considerably gives a root-mean-square scatter of 15%. This is reduced to ∽10% when elastic scattering effects are modelled by a simple analytical expression. © 1998 John Wiley & Sons, Ltd.