Matrix dependence of elastic scattering effects in quantitative AES and XPS

An involved Monte Carlo algorithm has been developed for simulating the Auger electron and photoelectron trajectories in the surface region of different materials. The partial wave expansion method was applied to describe the electron elastic scattering. Extensive calculations were performed for C 1s photoelectrons emitted from carbon implanted in a number of materials with atomic number varying from 6 to 79. It has been found that elastic collisions influence considerably the angular distribution of photoelectrons. The asymmetry parameter describing the actual distribution decreases owing to photoelectron elastic scatering. This effect becomes more pronounced with increase of atomic number of a matrix. Two correcting parameters in quantitative XPS formalism are proposed to account for elastic scattering effects. The analytical expressions are determined to describe these correcting parameters as a function of (i) matrix atomic number, (ii) matrix atomic density, and (iii) radiation used. Similar analysis was made for carbon KLL Auger transition. Elastic Auger electron collisions were demonstrated to decrease up to 15% the Auger signal intensity. No distinct changes in angular distribution of Auger electrons were observed. An analytical expression was fitted providing the signal intensity decrease as a function of matrix atomic number and atomic density.