Electronic interactions at SiO2/M′Ox (M′: Al, Ti) oxide interfaces

The electronic interactions at SiO2/TiO2 and SiO2/Al2O3 interfaces have been studied by X-ray photoemission spectroscopy. Both interfaces were formed by deposition of SiO2 (evaporation of silicon monoxide followed of oxygen plasma treatment) on the surface of TiO2 and Al2O3 substrates. The variation of the binding energy (BE) of the Si 2p peaks and Auger parameter of silicon from the SiO2 deposits is followed as a function of coverage. The BE of Si 2p peaks of the Si atoms at the SiO2/TiO2 (SiO2/Al2O3) interface decreases 1.3 eV (1.0 eV) from submonolayer coverages up to the bulk SiO2 material. Simultaneously, the Auger parameter of Si varies +0.9 eV (−0.3 eV). These changes are discussed in terms of initial and final state effects of the photoemission process. Quantum mechanical calculations with cluster models confirm the origin of the observed shifts in these parameters. These findings preclude the systematic use of BE as an absolute parameter to determine the chemical state of elements at oxide interfaces.