Regensburg 2022 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 66: Oxide Surfaces 2

O 66.5: Vortrag

Donnerstag, 8. September 2022, 11:45–12:00, S053

Structural analysis of complex 2D Sr-Ti-O/Pd(111) films. — •Martin Haller, Sebastian Schenk, Stefan Förster, and Wolf Widdra — Martin-Luther-Universität Halle-Wittenberg, Institute of Physics, Von-Danckelmann-Platz 3, 06120 Halle, Germany

In 2013 the first 2D oxide quasicrystal (OQC) in thin Ba-Ti-O/Pt(111) films with astonishing structural properties has been discovered [1]. It features a twelvefold rotational symmetry that is incompatible with lattice periodicity. Instead, it is described with a self-similar quasicrystalline structure that involves squares, triangles and rhombuses. In the wake of this discovery combinations of ternary oxide layers and different hexagonal substrates have been investigated to study the epitaxial preconditions for the formation of the OQC. In this contribution, we present a structural analysis for Sr-Ti-O on Pd(111). Globally, as seen from LEED, it forms a periodic structure with unit cell parameters a = 1.32 nm, b = 2.96 nm and α=93.43^∘. However, locally a second phase has been identified in atomically-resolved STM data with twelvefold symmetric FFT and long range coherence in the 2D auto-correlation image. The analysis of the tiling statistics reveals a triangle:square:rhomb ratio of 2.84:1:0.39 which deviates slightly from the ideal OQC’s ratio of 2.73:1:0.37 [2]. The given structure is discussed in terms of a disordered OQC which is further supported by a 4D hyperspace analyis.
[1] S. Förster et al., Nature 502, 215 (2013)
[2] S. Schenk et al., J. Phys. Condens. Matter, 29 (2017)