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O: Fachverband Oberflächenphysik
O 10: Oxides I: Growth and Characterization
O 10.10: Vortrag
Montag, 16. März 2020, 12:45–13:00, WIL B321
Oxide quasicrystal formation on Pd(111) — •Friederike Wührl1, Oliver Krahn1, Stefan Förster1, and Wolf Widdra1,2 — 1Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle(Saale), Germany — 2Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle(Saale), Germany
The discovery of a quasicrystalline phase in ultrathin films of BaTiO3 (BTO) on Pt(111) opened a new field of research on ternary oxides on metal substrates. Its observation was the first example for spontaneous formation of an aperiodic dodecagonal structure at the interface to a periodic crystal. So far oxide quasicrystals (OQC) have been found only on the surface of Pt(111) [1]. Here we report on the first OQC on an alternative substrate, namely Pd(111). Pd(111) has a 1% reduced lattice parameter as compared to Pt(111). LEED and STM data show several long-range-ordered wetting layer structures between 3D BaTiO3(111) islands after heating the film under UHV conditions. The diffraction spots of the BTO-islands show a Moiré pattern. The wetting layer structures finally converge at a temperature of 960 K to 1000 K into two domains of dodecagonal OQC’s, which are rotated by ± 5∘ against the high symmetry directions of the substrate. This dodecagonal structure coexist with another wetting layer structure. Surprisingly, the characteristic length of the newly discovered BTO-derived OQC is reduced according to the smaller lattice parameter.
[1] S. Förster et al., Phys. Status Solidi B, doi: 10.1002/pssb.201900624, (2019)