Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 74: Oxide and Insulator Surfaces
O 74.1: Poster
Wednesday, March 18, 2015, 18:15–21:00, Poster A
Archimedean snub square tiling in a BaTiO3 derived epitaxial film on Pt(111) — Martin Trautmann1, Stefan Förster1, Florian Schumann1, Christian Teichert1,2, •Klaus Meinel1, and Wolf Widdra1,3 — 1Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, D-06099 Halle, Germany — 2Institute of Physics, Montanuniversität Leoben, A-8700 Leoben, Austria — 3Max-Planck Institut für Mikrostrukturphysik, D-06120 Halle, Germany
Under specific conditions, ultrathin BaTiO3 films on Pt(111) develop a 2D quasicrystalline structure of twelve-fold rotational symmetry which is composed by an aperiodic arrangement of triangular, quadratic, and rhombic tiling elements [1]. Searching for the basic mechanisms of its formation, a periodic approximant has been identified. It merely consists of the triangular and quadratic elements of the quasicrystal that arrange in a snub square tessellation. In vertex notation, this structure can be described as (3.3.4.3.4) pattern, which has already been considered by Kepler in his general analysis of Archimedean tilings [2]. Applying STM, LEED, and SPA-LEED, the corresponding lattice parameters and the epitaxy matrix with respect to the Pt(111) substrate are determined with high precision. STS indicates that Ti3+-O vacancy clusters are constituents of that structure similar to the case which has been deduced for the quasicrystal. The film structure found is an important additional nanoscale observation of the - hitherto rare - five-vertex motives in 2D interface tessellations.
[1] S. Förster, et al., Nature 502, 215 (2013).
[2] J. Kepler, Harmonices Mundi, Johannes Planck, Linz (1619).