ION-BEAM EFFECTS ON SURFACE AND SUBSURFACE COMPOSITION OF NEAR-NOBLE SILICIDES

Modifications of Cr–silicide (Cr3Si and CrSi2) and Ni–silicide (NiSi2) surface and subsurface regions induced by an Ar ion beam were investigated by angle integrated Auger electron spectroscopy. The dependence of the surface modification on the ion beam energy and density was investigated between −80 and 400 °C. At room temperature (RT) Cr–silicides are metal enriched in the surface and subsurface region. Ion bombardment of a CrSi2 surface at high temperature (HT) produces Si enrichment with respect to RT, resulting in the formation of a CrSi layer. The Si enrichment occurs at a temperature lower than the temperature characteristic of purely thermal segregation. On the contrary, the Cr3Si surface composition is independent of the temperature. The NiSi2 surface is stoichiometric at RT; ion bombardment at HT produces a Si surface segregation in two distinct steps. On the basis of a careful line‐shape analysis of the Si core–valence–valence Auger transitions, we attribute the first step to the formation of an ordered, ∼1.4 Å thick, Si overlayer, the second one to the growth of a thicker (∼3 Å) amorphous Si layer.