Quantitative AES: Via the inelastic mean free path or the attenuation length?

Abstract

AbstractThe terms inelastic mean free path (IMFP) and attenuation length (AL) of electrons in solids are described by different definitions and their values may differ profoundly, by >30%. For this reason, it is of crucial importance to decide which term should be used in calculations for quantitative AES analysis. An attempt to answer this question is made in the present work. The Monte Carlo algorithm was developed to simulate the Auger electron transport in metal alloys. Calculations were made for Auger electrons emitted in the Al48Ni52 ordered alloy and the corresponding standards. Comparison with the usual mathematical formalism of AES shows that elastic collisions of Auger electrons can be accounted for by two correcting parameters: (1) a correction denoted by Q, which accounts for the decrease of the Auger electron current; (2) a correction denoted by K, which accounts for the decrease of the depth of analysis. It was proved that the total correcting factor comprises four groups of parameters: atomic densities, back‐scattering factors, inelastic mean free paths and corrections Q. Thus, we obtain the unexpected result that the calculations for quantitative AES require knowledge of the IMFP rather than the AL. The parameter Q is usually close to unity and can be neglected. The use of attenuation lengths in calculations may result in considerable errors. However, it is possible to recalculate values for the AL to obtain the IMFP.