The energy band alignment at interfaces between different materials is a key factor, which determines the function of electronic devices. While the energy band alignment of conventional semiconductors is quite well understood, systematic experimental studies on oxides are still missing. This work presents an extensive study on the intrinsic energy band alignment of a wide range of functional oxides using photoelectron spectroscopy with in‐situ sample preparation. The studied materials have particular technological importance in diverse fields as solar cells, piezotronics, multiferroics, photo‐electrochemistry and oxide electronics. Particular efforts have been made to verify the validity of transitivity, in order to confirm the intrinsic nature of the obtained band alignment and to understand the underlying principles. Valence band offsets up to 1.6 eV are observed. The large variation of valence band maximum energy can be explained by the different orbital contributions to the density of states in the valence band. The framework provided by this work enables the general understanding and prediction of energy band alignment at oxide interfaces, and furthermore the tailoring of energy level matching for charge transfer in functional oxides. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In this investigation, we studied electronic properties of the CdS∕Zn1−xMgxO (x=0,0.15) interface using photoelectron spectroscopy. ZnO and (Zn,Mg)O films were deposited by magnetron sputtering from ceramic targets on thermally evaporated CdS. Valence-band offsets of ΔEV=1.2±0.1eV are determined for both interfaces. The gap difference of 0.3eV between ZnO and Zn0.85Mg0.15O is therefore fully accommodated by a different conduction-band energy, which should be well suited for modulation doping in ZnO∕(Zn,Mg)O heterostructures.

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As an origin of degradation of remnant polarization in Pt/ BaTiO 3 / Pt capacitor structure, an interfacial layer formed at the interface of BaTiO 3 film and a Pt bottom electrode is considered. BaTiO 3 films were deposited on two types of bottom electrodes ͑La 0.5 Sr 0.5 CoO 3 and Pt͒ by the radio frequency magnetron sputtering method and both capacitors showed a microstructural similarity with strong preferred orientations. However, a Pt/ BaTiO 3 /La 0.5 Sr 0.5 CoO 3 capacitor exhibited a saturated hysteresis loop with the remnant polarization ͑2P r ͒ of 6 C/cm 2 , and for the Pt/ BaTiO 3 / Pt structure, the polarization-voltage curve revealed a linear dielectric characteristic. From a cross-sectional high-resolution transmission electron microscope analysis of the Pt/ BaTiO 3 / Pt capacitor showing the linear dielectric property, an interfacial layer with an amorphous structure as well as a multidomain structure in the interior of the BaTiO 3 film were observed. It is concluded that the interfacial layer might help degradation of polarization and its origin can be classified as being extrinsic.

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