On the formation of concentration profiles by low-energy ion bombardment and sputter depth profiling

An analytical model is developed to describe the generation of concentration profiles in binary solids under low-energy ion bombardment. The model accounts, in particular, for preferential sputtering and radiation-enhanced particle transport in the solid, and is found to apply for a quantitative representation of steady-state concentration microprofiles in the near surface region of initially homogeneous binary targets as Fe-silicides. A model-based evaluation of such profiles delivers absolute values of the corresponding coefficients for radiation-enhanced diffusion. The numerical solution enables to trace the profile evolution in dependence of the bombarding time or ion fluence. When being applied to sputter depth profiling of a pre-existing concentration profile, a severe influence of the actual sputter yield ratio of the target components is found which may completely deteriorate the characteristics of the profile to be analyzed