Photoelectron Si 2p spectra of ultrathin CoSi2 layers formed on Si(100)2×1

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Solid-phase formation of ultrathin CoSi2 layers on Si(100)2×1 was studied using high-resolution (∼140 meV) photoelectron spectroscopy with synchrotron radiation (hν=130 eV). The evolution of Si 2p spectra was recorded both under deposition of cobalt on the surface of samples maintained at room temperature and in the course of their subsequent annealing. It was shown that Co adsorption on Si(100)2×1 is accompanied by a loss of reconstruction of the original silicon surface while not bringing about the formation of a stable CoSi2-like phase. As the amount of deposited cobalt continues to increase (up to six monolayers), a discontinuous film of the Co-Si solid solution begins to grow on the silicon surface coated by chemisorbed cobalt. The solid-phase reaction of CoSi2 formation starts at a temperature close to 250°C and ends after the samples have been annealed to ∼350°C.