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Paper AS-MoA3
Quantitative AES and XPS - Databases Test Quantification Validity

Monday, October 29, 2001, 2:40 pm, Room 134

Session: Quantitative Analysis and Data Interpretation II: Electron Spectroscopies
Presenter: M.P. Seah, National Physical Laboratory, UK
Authors: M.P. Seah, National Physical Laboratory, UK
I.S. Gilmore, National Physical Laboratory, UK
S.J. Spencer, National Physical Laboratory, UK
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For quantitative analysis by AES and XPS we may either use theoretical or experimental sensitivity factors (SFs). In the past, many analysts have used experimental SFs deduced from data for pure elements or have calculated such data. Both of these will lead to erroneous results. It is shown that the correct SFs for analysing homogeneous mixtures are those deduced for a common, or average, matrix.@footnote 1@ These may be calculated according to easily defined rules.@footnote 1,2@ Experimental SFs from NPL databases for AES and XPS agree closely with theory apart from one factor that varies from element to element but is the same for AES as for XPS and is independent of the electron emission energy. This factor is attributed to an inadequacy either of the background subtraction method for the experimental peak areas or of the material-to-material dependence of the inelastic mean free path (IMFP) for the theory. A number of improvements have been made in the background subtraction method which now uses data from an angle-averaged REELS database@footnote 3@ instead of the Tougaard method. The background subtracted XPS spectra have intrinsic loss intensities that are consistent with theoretical predictions. Analyses show that the main error may come from the material-to-material dependence of the IMFP but that the new average matrix sensitivity factors avoid this error. Apart from the single factor for each element, which is the same for AES as for XPS, the correlations between experiment and theory exhibit scatters of 8% and 11% for AES and XPS, respectively. These correlations are shown to be valid in AES for K, L, M or N shell Auger electron peaks with kinetic energies above 180 eV and in XPS for all shells except the weak s shells for Z > 20. @FootnoteText@ @footnote 1@M P Seah and I S Gilmore, Surf. Interface Anal. 26(1998)908. @footnote 2@M P Seah, I S Gilmore and S J Spencer, J. Elec. Spectrosc. to be published. @footnote 3@M P Seah, Surf. Sci. 471(2001)782.