Interaction of cobalt with the Si(1 0 0)2 × 1 surface studied by photoelectron spectroscopy

Cobalt adsorption and condensation on the Si(1 0 0)2 × 1 surface as well as solid-phase reaction of CoSi2 formation have been studied by high-resolution photoelectron spectroscopy with synchrotron radiation. We have measured the Si 2p and valence-band spectra after the Co deposition from a submonolayer coverage to 6 ML thickness and a subsequent annealing to 600 °C. Room temperature Co adsorption results in the loss of the initial surface reconstruction, and the chemisorbed Co atoms appear to be embedded into the upper layer of Si(1 0 0); however, no stable CoSi2 was observed. With further metal deposition, a discontinuous solid solution CoSi film was formed and the dissolved Si concentration decreased with the distance from the crystal surface. The formation of cobalt disilicide was found to occur in the range of 250-400 °C.