Enhanced silicon oxidation on titanium-covered Si(001)

We report on a core level photoemission study of the formation of an ultrathin SiOx layer grown at the interface of a titanium-covered Si(001) surface. Oxygen exposure at room temperature induces a large chemical shift of the Si 2p state, predominantly assigned to Si4 + . The results indicate that a SiO2 − δ layer, close to the stoichiometry of SiO2, is formed below the TiOx film. The thickness of the SiO2 − δ layer is estimated to be ~ 0.9 nm, corresponding to three to four oxide layers. Further chemical shift caused by annealing is attributed to the formation of titanium silicate (TiSixOy).