Cobalt disilicide epitaxial growth on the silicon (111) surface

Initial stages of CoSi₂ formation on the silicon (111) surface were investigated by low-energy electron diffraction (LEED), x-ray photoemission spectroscopy (XPS), and angle-resolved ultraviolet photoemission spectroscopy (ARUPS) techniques under ultrahigh-vacuum conditions. At room temperature, a small amount of Co evaporated onto Si reacts strongly with Si atoms to form cobalt silicide. With increasing coverage (Θ>4 monolayers) results from surface techniques indicate an enrichment of the metal in the probed region and the ultraviolet photoemission spectroscopy spectrum resembles that of a Co bulk metal. The behavior of these metal-silicon interfaces with annealing at {~}600^∘{}C under ultrahigh-vacuum conditions was also examined. In the submonolayer range, two LEED superstructures, √7×√7 and 2×{}1, are found, while at higher coverage the formation of an epitaxial CoSi₂ film can be achieved. First experimental ARUPS measurements of the interface are presented and compared to very recent calculations.