Quantitative AES IV: Accuracy of the Numerical Evaluation of Peak Areas in AES using the Universal Tongaard Background Subtraction Method

A study is made of the Tougaard background subtraction method for homogeneous materials for determining the true peak area in Auger electron spectroscopy (AES) where the peak structure extends over a wide energy range and where knowledge of the true characteristic loss background is unavailable. The effects of increased intensity in the inelastically scattered background are analysed using a model spectrum with the background subsequently removed using the Tougaard Universal function but with various values of the Tougaard parameters B and C. It is shown that the full peak areas depend on the value of B/2C. The analysis is then extended to Auger electron peaks on a power law cascade background. By a suitable procedure the sensitivity of the area to the value of B/2C may be reduced. Furthermore, by using the area of the highest energy Auger electron peak, on its own, or by using area ratios for elements, the errors are reduced to below 2%. It is recommended that for absolute intensities using theoretical cross-sections the full area with the universal values of B=2866 eV2 and C=1643 eV2 should be used, whereas for quantitative AES with relative sensitivity factors the partial area of the highest energy peak analysed with the same values of B and C is a better measure.