“In situ” XPS study of band structures at Cu2O/TiO2 heterojunctions interface

In an attempt to investigate influence of the defects on electronic structure of Cu2O/TiO2 heterojunctions, thin Cu2O layers were successively deposited on TiO2 that has different levels of defect concentrations, and the resultant band bending and offset characteristics were studied by in situ X-ray photoelectron spectroscopy (XPS). The TiO2 substrates with defects were prepared by Ar+ sputtering, followed by annealing at different temperatures in oxygen atmosphere. Presence of the defects in TiO2 surface dramatically influences on the band bending and band offset at the interface: more defects are on TiO2 surface, less band bending are at the interface, inducing smaller conduction band offsets. On the reduced TiO2 surface, Cu2O was disproportionately decomposed to form CuO and Cu.