Incommensurability imposed by the low-temperature phase transition at the (0 0 1) surface of SrTiO 3

Abstract

The reflection high-energy electron diffraction (RHEED) study of the SrTiO 3 (0 0 1) surface structure in the temperature region from 6 to 300 K shows the “anomalous” growth of the surface lattice parameters under the temperature decrease. This behavior is ascribed to the specific character of the low-temperature phase transition connected with the rotation of the metal-centered oxygen octahedra around the normal to the (0 0 1) surface. RHEED intensities analysis based on R-factor minimization shows that the best-fit between the experiment and calculations is reached for oxygen octahedra rotations which are essentially different for two (0 0 1) surface terminations SrO and TiO 2. Octahedra rotations were assumed to give rise to an increase of the surface lattice parameters resulting in the fact that incommensurability between the bulk and surface parameters inevitably arises. The histogram method applied to the set of lattice parameter values shows the discrete character of the distribution obtained.