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 ($\ensuremath{\Theta}>4$ 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 \ensuremath{\sim}600\ifmmode^\circ\else\textdegree\fi{}C under ultrahigh-vacuum conditions was also examined. In the submonolayer range, two LEED superstructures, $\sqrt{7}\ifmmode\times\else\texttimes\fi{}\sqrt{7}$ and 2\ifmmode\times\else\texttimes\fi{}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.