Ni/Si(111) system:: Formation and evolution of two- and three-dimensional phases studied by spectromicroscopy

The spatial variations in the composition and electronic structure of Ni/Si interfaces formed via reactive epitaxy at 830 K and successively annealed to 950 K have been studied by synchrotron-radiation scanning photoelectron microscopy, a method that combines chemical mapping with photoelectron spectroscopy from selected spots of the surface. The combination of submicron spatial resolution (less than or equal to 0.15 mu m) with high energy resolution allowed us to characterize the coexisting phases including micron-sized silicide islands and two-dimensional structures. Deposition of 0.7 ML Ni at 830 K produced domains of the root 19 phase with different Ni concentration, coexisting with NiSi and NiSi2 islands. Annealing this interface to 950 K led to conversion of the root 19 to a (1 x 1)-RC structure (where RC is ring cluster), which appears to be more uniform than the root 19 surface. From the chemical maps and the Si 2p, Ni 3p, and valence-band spectra corresponding to the coexisting phases the nature of the phases was determined and the mechanism of the Ni mass transport on the root 19 and (1 x 1)-RC surfaces was examined. [S0163-1829(99)08903-1].