Dissociative adsorption of O₂ and H₂O on Si(113): chemical shifts of the Si 2p level

Using high-resolution Si 2p surface core-level spectroscopy, dissociative adsorption of O2 and H2O was studied on the Si(113)-(3 × 2) surface. Dissociation of O2 gives rise to the known chemically shifted Si 2p components of Si1+ (−930 meV, shifted the larger binding energy), Si2+ (−1760 meV), Si3+ (−2510 meV), and Si4+ (−3500 meV). The relative abundance of the Si2+ component lies between those for the Si(001) and Si(111) surfaces. Following dissociative adsorption of H2O, H-derived (at −220 meV) and OH-derived (at −900 meV) surface core-level shifts were observed. The dissociative adsorption is found to be similar to that on Si(001), lending support to the recent structure model of the Si(113) surface which assumes Si dimers as constituents at the surface. Annealing to higher temperatures leads to a decomposition of the OH group into H and O which desorb sequentially at higher temperatures. 5–10% of the H2O saturation dose leads to quenching of the Si(113)-(3 × 2) surface states and to a pinning of the Fermi level at 730 meV above the valence-band maximum