Electronic interaction at the TiO2–Al2O3 interface as observed by X-ray absorption spectroscopy

Abstract The electronic structure of the TiO 2 –Al 2 O 3 interface has been studied using X-ray absorption spectroscopy. Special attention has been paid to the early stages of growth, i.e. the sub-monolayer regime ( θ 2 indicating the presence of interfacial states. The spectra have been compared with atomic multiplet calculations reported in the literature. From this comparison it is concluded that strong electronic interactions occur at the interface, as deduced from the significant lowering of the crystal field of the Ti atoms at the interface (1.0 eV) as compared with bulk TiO 2 (1.8 eV). It is suggested that the important covalent character of the bonding of the Al 2 O 3 substrate is the responsible of this crystal field lowering.