Heteroepitaxial registry and band structures at the polar-to-polar STO/ZnO (000(1)over-bar) interfaces

The interface between ZnO and SrTiO3 (STO) provides a paradigm for combining perovskite oxides and wurtzite-structure semiconductors. However, the heteroepitaxial and energy band structures of the polar-to-polar STO/ZnO(000 (1) over bar) interfaces has rarely been studied. In this study, it is shown that the STO films prepared on the ZnO (000 (1) over bar) substrate by pulsed laser deposition possess [011](STO) and [111](STO) azimuth orientations, which exhibit three- and two-fold rotation domains respectively, as demonstrated by X-ray diffraction and transmission electron microscopy. The band structures of the STO(011)/ZnO (000 (1) over bar) and STO(111)/ZnO(000 (1) over bar) interfaces are bending downward as shown in the I-V characteristic spectra and first principle calculations. These results are different from the single orientation ZnO films grown on STO-(011) and -(111) substrate, as reported in previous literatures, showing the heteroepitaxial asymmetry between STO/ZnO and ZnO/STO interfaces. This work presents an approach towards the physical modeling of combinations between perovskite oxides and wurtzite-structure semiconductors.