Reexamination of band offset transitivity employing oxide heterojunctions

Band offset transitivity is reexamined extendedly by employing oxide heterojuctions. The valence band offsets (DEV) at HfO2/SiO2, Al2O3/SiO2, and HfO2/Al2O3 heterojunctions are experimentally determined to be 0.81, 0.25, and 0.25 eV, respectively, by X-ray photoelectron spectroscopy. Thus, the DEV at HfO2/Al2O3 heterojunction is not equal to the DEV at HfO2/SiO2 minus the DEV at Al2O3/SiO2 heterostructures (0.25 6？0.81 0.25？0.56), i.e., the transitivity rule fails for oxide heterojunctions. Different distributions of interfacial induced gap states at the three heterostructures contribute to this failure of transitivity rule.