Reexamination of band offset transitivity employing oxide heterojunctions

Band offset transitivity is reexamined extendedly by employing oxide heterojuctions. The valence band offsets (Delta E-V) 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 Delta E-V at HfO2/Al2O3 heterojunction is not equal to the Delta E-V at HfO2/SiO2 minus the Delta E-V at Al2O3/SiO2 heterostructures (0.25 not equal 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. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4789392]