Exploring the antiferrodistortive phase of strained SrTiO3 thin films

The prototypical perovskite SrTiO3, while being an incipient ferroelectric in bulk, is known to possess a structural transition at 105 K, where subtle rotations of the oxygen octahedra double the cubic unit cell resulting in a tetragonal antiferrodistortive (AFD) phase. So far, relatively little attention has been paid to the effect of biaxial strain on the AFD transition of strained SrTiO3 thin films, and if and how it interacts with ferroelectricity. To understand these questions, we propose to perform cryogenic diffuse scattering experiment at ID28 on SrTiO3 films grown under different amount of biaxial strain and on substrates of different symmetry. This experiment requires the capability of the ID28 beamline at ESRF to capture a large volume of the reciprocal space and detect the very weak scattering produced by the subtle oxygen rotations in the AFD phase.