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O: Fachverband Oberflächenphysik
O 75: Overview Talk: Ulrike Diebold
O 75.1: Hauptvortrag
Donnerstag, 10. März 2016, 09:30–10:15, S054
Surface Structure and Reactivity of Selected Perovskite Oxides — •Ulrike Diebold — Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
Ternary oxides with the perovskite structure exhibit an intriguingly rich variety in their physical and chemical properties. The surfaces of these promising, yet complex materials are poorly understood. In the talk I will provide an overview of surface studies of perovskite oxides, and, for a few examples, discuss optimum preparation parameters for a reproducible surface structure and how this affects reactivity and growth.
The surface of Sr3Ru2O7, the n=2 member of the Ruddlesden-Popper series, is structurally quite simple: cleaving in UHV yields a SrO-like top layer, which is essentially defect-free, except for impurities in the bulk material. The surface is very reactive towards components of the residual gas, however. CO, CO2, and H2O adsorb readily and form adsorption complexes. SrTiO3(110) is polar and exhibits a series of reconstructions that can be controlled by adjusting the chemical potential of its constituents, i.e. by evaporating appropriate amounts of Sr and Ti and annealing in O2. The (n×1) reconstructions consist of a monolayer of titania with tetrathedrally-coordinated Ti atoms that are arranged in corner-sharing rings. When the Ti chemical potential is increased, the surface switches over to a (2×m) symmetry with a titania layer that is composed of Ti in octahedral coordination. These stoichiometry-dependent, facile structural changes have a profound effect on surface reactivity, and on the homoepitaxial growth of SrTiO3 during pulsed laser deposition.