High-temperature nucleation and silicide formation at the Co/Si(111)-7×7 interface: A structural investigation

We have investigated the atomic structure of annealed Co/Si(111) interfaces prepared by the evaporation of one-, two-, and thirty-monolayer equivalent coverages of Co. Experimental and theoretical angular distributions of the Co LMM Auger intensity reveal that for all coverages investigated a ${\mathrm{CoSi}}_2$ phase forms which is rotated 180° about the surface normal relative to the substrate. At low coverages, the ${\mathrm{CoSi}}_2$ phase is in the form of clusters which appear to be two to three ${\mathrm{CoSi}}_2$ layers in thickness and are terminated by a Si(111) bilayer. The Si(111) overlayer, which is in addition to the terminal plane of Si atoms associated with the outermost ${\mathrm{CoSi}}_2$ layer, also appears to be rotated 180° about the surface normal relative to the Si substrate.