Oxidation of a Si(001) surface mediated by repetitive adsorption/desorption cycles of Cs: a metastable deexcitation spectroscopy study

We have investigated, by metastable deexcitation spectroscopy (MDS), the initial stage of SiOxSi(001) interface formation with repetitive oxidation cycles consisting of promoted oxygen-uptake by preadsorbed caesium followed by annealing. MDS spectra from Cs-adsorbed SiOx(001)Si surfaces were similar to that from a CsSi(001) surface showing sharp Cs 6s̃ peaks just below EF, although oxygen atoms are included at the former substrate surface. The Cs atoms at the former surfaces played the same role of transferring electrons to oxygen enhancing the oxygen uptake rate as that observed at the latter surface. We explored an evolution of the valence-band states at topmost atomic layers in the progress of alkali-assisted oxidation.