Quantitative AES VII. The ionization cross-section in AES

Abstract

Inner shell ionization cross-sections are analyzed for use with Auger electron spectroscopy (AES). Correlations of the cross-sections of Gryzinski, Casnati et al., Jakoby et al., and Drawin are made with experimental data from the digital Auger database. Jakoby et a/.'s cross-section is realistic for K shell ionizations but can become negative for other shells unless modified, so is of limited use for AES. Results for the ratios of experimental and calculated intensities for electron beam energies of 5 keV and 10 keV, for overpotentials in the range 2-60, are used to rank the effectiveness of the remaining three cross-sections. The experimental ratios show means and scatter standard deviations of 1.01±0.12, 0.99±0.05 and 1.04±0.09 when compared with the predictions for the cross-sections of Gryzinski, Casnati et al. and Drawin, respectively. Casnati et al.'s cross-section provides the best correlation, with the goodness of fit being similar for ionizations in the K, L, M and N shells. Casnati et al.'s cross-section is therefore recommended for future use in AES. The use of Gryzinski's or of Drawin's cross-sections, by comparison, can lead to errors as high as 50% at the low value of 1.5 for the overpotential (i.e. for high-energy Auger electrons), © Crown copyright 1998.