Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 51: Oxides and insulators: Epitaxy and growth
O 51.7: Vortrag
Mittwoch, 28. März 2012, 18:15–18:30, HE 101
STM and LEED investigation of a quasicrystalline thin film phase of BaTiO3 on Pt(111) — •Stefan Förster1, Klaus Meinel1, Karl-Michael Schindler1, and Wolf Widdra1,2 — 1Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany — 2Max Planck Institute of Microstructure Physics, Halle, Germany
BaTiO3 is the most studied ferroelectric perowskite which has an easily accessible ferroelectric to paraelectric phase transition at about 400 K. It can be grown epitaxially on Pt(100) and Pt(111) due to its small lattice mismatch of only 2% relative to the substrate. Upon annealing in an oxygen atmosphere well-ordered BaTiO3(100) and BaTiO3(111) thin film phases have been reported [1]. However, here we report on a surprising thin film phase upon annealing in UHV. For 4 ML BaTiO3 on Pt(111), annealing at 1250 K leads to the formation of large three-dimensional islands of bulk-like BaTiO3. Between these islands, the Pt terraces are covered by a remaining BaTiO3 wetting layer.
By means of low-energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) the structure of this wetting layer has been identified to be a 2D quasicrystalline phase of BaTiO3. In LEED this structure shows bright and sharp spots with dodecagonal symmetry. STM reveals that the surface structure is composed by an arrangement of quadratic and triangular building blocks which can explain the 2D quasicrystalline lattice with dodecagonal symmetry.
[1] S. Förster, M. Huth, K.-M. Schindler, and W. Widdra, J. Chem. Phys. 135, 104701 2011.