Phase-formation diagram for precursors to epitaxial growth of NiSi2 on Si(111)

Using reflection high-energy electron diffraction and Auger microanalysis in a custom-built ultrahigh vacuum scanning electron microscope we have identified six ordered structures that precede epitaxial NiSi2 during the annealing of nickel overlayers on Si(111). A novel technique of depositing through holes in a mask positioned near the sample allows us to obtain the complete coverage dependence of these structures in a single annealing cycle. The role of these structures in relation to the NiSi2 (B) (twinned) and NiSi2 (A) (nontwinned) structures is described.