ACCURACY OF THE NONDESTRUCTIVE SURFACE NANOSTRUCTURE QUANTIFICATION TECHNIQUE BASED ON ANALYSIS OF THE XPS OR AES PEAK SHAPE

The accuracy of XPS and AES quantification by peak shape analysis was established from a detailed analysis of a range of model spectra and t hree sets of experiments. It was found that information on the concent ration-depth profile in the surface region up to depths of similar to 5 lambda(i) (where lambda(i) is the inelastic electron mean free path) is primarily contained in the spectral energy region up to similar to 100 eV below the peak energy and is essentially completely contained by the energy region up to similar to 200 eV below the peak. Analysis of a larger energy range than 100 eV does not add much to the informat ion on the details of the structure in the outermost 5 lambda(i) but g ives the possibility to determine additional structural parameters tha t describe the composition at larger depths. The structural parameters that describe the chemical composition of the outermost 5-10 lambda(i ) 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 se condary parameters are parameters other than the three primary paramet ers that describe the finer details of the depth distribution of atoms in the outermost 5-10 lambda(i) of the surface region. The uncertaint y in the determined three primary parameters is typically 5-10%. The u ncertainty in the determined secondary parameters is typically greater than or similar to 35%. Different models of depth profiles can be dis tinguished when they differ significantly over a width of more than si milar to 1/3 lambda(i) at any depth less than or similar to 5 lambda(i ). The uncertainty in the total determined amounts of atoms within the surface region is similar to 5-10% as long as the depths are within t he primary probing depth of the method (i.e. <5 lambda(i)). The absolu te quantification of a set of samples where the in-depth distribution varies considerably gives a root-mean-square scatter of 15%, This is r educed to similar to 10% when elastic scattering effects are modelled by a simple analytical expression. (C) 1998 John Wiley & Sons, Ltd.