Cobalt disilicide epitaxial growth on the silicon (111) surface

Abstract

Initial stages of Co${\mathrm{Si}}_2$ 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 ($\Theta >4\mathrm{}$ 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, $\sqrt{7}\times \sqrt{7}$ and 2×1, are found, while at higher coverage the formation of an epitaxial Co${\mathrm{Si}}_2$ film can be achieved. First experimental ARUPS measurements of the interface are presented and compared to very recent calculations.