ANALYTICAL EXPRESSION DESCRIBING THE ATTENUATION OF AUGER ELECTRONS AND PHOTOELECTRONS IN SOLIDS

The attenuation of Auger electrons and photoelectrons in solids, as described by the so-called depth distribution function (DDF), has been studied by means of a Monte Carlo simulation of electron transport in matter. Elastic scattering plays a significant role in the model. Based on the results of a large number of simulations, an empirically derived analytical expression for the DDF is proposed that includes the effects of elastic scattering. As part of this analytical DDF, a new attenuation parameter (AP) is introduced, which, being a material constant independent of emission angle and layer thickness, can assume a central role in quantitative AES and XPS. The proposed AP as well as the general validity of the results is discussed. Most importantly, a simple relationship between the most significant quantities governing the transport of electrons in solids, i.e. the inelastic mean free path (IMFP), the total mean free path (TMFP) and the attenuation parameter, was derived from the results. By a single Monte Carlo simulation, the AP can be determined. The DDF for different experimental geometries, film thicknesses, etc. can then be determined analytically.