Band Alignment at the Cu 2 O/ZnO Heterojunction

The band offset at the Cu 2 O/ZnO heterojunction was estimated both experimentally and theoretically following the procedure of core-level spectroscopy. The heterojunction was fabricated by electrochemical deposition, and the band offset was determined by X-ray photoelectron spectroscopy. For the theoretical calculation of the band offset, the first-principles, density-functional, pseudopotential method was used. It was predicted from both the experimental and calculation results that the valence band maximum of Cu 2 O is located higher than that of ZnO. The experimentally obtained valence band offset Δ E v was 1.7 eV, and the theoretically obtained Δ E v was 1.3–1.6 eV; both results agreed fairly well.