Imaging of the structure of ultra-thin cobalt silicide films by inelastically backscattered electrons

We have investigated the initial growth of cobalt silicide films in the Co/Si(1 1 1) system by incoherent medium-energy electron diffraction providing real-space imaging of the subsurface atomic structure. It is shown that deposition of the first few (1–3) monolayers of Co results in formation of cobalt silicide islands with composition and structure depending on the temperature. While, the clusters of B-type CoSi2 grow at elevated temperatures (T>300°C), the room temperature deposits consist of silicide grains of A- and B-type orientation. Further increase of the Co coverage results in both an enrichment of the probed layer with the metal and its disordering. Annealing of such samples at T>250°C gives rise to solid-phase reaction of Co and Si leading to gradual formation of the epitaxial disilicide layer and disappearance of A-type domains.