Layer-resolved depth profiling at single crystal surfaces

The stopping power and straggling of ions in channeling and blocking directions depend on multiple scattering and impact parameter dependent effects. Therefore, the extraction of high-resolution depth profiles of single crystals based on simulation of the energy spectra obtained from medium-energy ion scattering (MEIS) is not straightforward. An alternative is to analyze the MEIS angular (blocking) scattering yields from several angular configurations. We have applied this technique to obtain layer-resolved depth profiles in a dilute substitutional alloy, Fe-9 wt% W (1 0 0), and in an alloy with a small mass difference between the base metals, Fe-15 wt% Cr (1 0 0). As a result, layer-resolved depth profiling combined with conventional MEIS structural analysis allowed a detailed study of surface segregation phenomena in these systems.