High-resolution photoemission study of Co/Si(111) interface formation

We have examined the formation of the Co/Si(111) interface at room temperature using high-resolution core-level photoemission spectroscopy. Two chemically shifted Si 2p core-level components have been identified. The evolution of these components with Co coverage makes it possible to model the development of this interface. Heterogeneous ${\mathrm{CoSi}}_2$-like cluster formation is observed for nominal Co coverages of less than ≊4 Å. Continued reaction to form ${\mathrm{CoSi}}_2$ becomes diffusion limited when the clusters coalesce, and a solid solution forms with Si atoms in a Co matrix. For Co coverages of more than 8–10 Å, the interfacial region is buried by a metallic Co film.