Linking the Electronic and Atomic Structure of Epitaxial Complex Oxides on Semiconductors

Understanding the interfacial coupling between materials with different electronic properties is critical to achieve the integration of epitaxial complex oxides with semiconductors. Using a combination of synchrotron x-ray diffraction and first principles calculations, we show that the electronic properties and atomic structure of epitaxial SrTiO$_{3}$ films on Si, and BaTiO$_{3}$ films on Ge are directly linked to the chemical composition at their respective interfaces. Sub-angstrom [001] cation-anion displacements observed in the SrTiO$_{3}$/Si system, lead to a positively polarized film. The polar distortions are found to arise from an interplay between compressive strain and localized interface states. In contrast to SrTiO$_{3}$/Si, we find that the BaTiO$_{3}$/Ge interface has a 2x1 structure that drives an in-plane polarization.