The atomic structure and polarization of strained $SrTiO3/Si$

For thin film devices based on coupling ferroelectric polarization to charge carriers in semiconductors, the role of the interface is critical. To elucidate this role, we use synchrotron x-ray diffraction to determine the interface structure of epitaxial $SrTiO3$ grown on the (001) surface of Si. The average displacement of the O octahedral sublattice relative to the Sr sublattice determines the film polarization and is measured to be about 0.05 nm toward the Si, with Ti off-center displacements 0.009 nm away from the substrate. Measurements of films with different boundary conditions on the top of the $SrTiO3$ show that the polarization at the $SrTiO3/Si$ interface is dominated by oxide-Si chemical interactions.