Influence of ion bombardment on depth resolution in Auger electron spectroscopy analysis of thin gold films on nickel

Thin film Auger electron analysis of gold films on nickel was performed while simultaneously sputtering with argon ions. The influence of film thickness, electron and ion beam energies, ion beam current density and initial surface roughness on depth resolution was investigated. The intrinsic limitations of depth resolution result from the escape depth of Auger electrons and from atomic mixing due to ion impact. Prolonged ion sputtering leads to the development of microroughness. The influence of this last effect is described by an empirical correlation which shows the width of the transition region to increase with the square root of the product of ion beam energy and film thickness. The original surface roughness also affects depth resolution but, at higher ion beam energies (2 keV) in particular, its influence is somewhat masked by ion-induced microroughness. Optimum resolution (5% of film thickness) in depth profiling is obtained by employing well-polished samples and low ion beam energies.