Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 49: Oxide and Insulator Interfaces I

O 49.3: Vortrag

Mittwoch, 20. März 2024, 11:00–11:15, MA 144

Observation of a dodecagonal europium oxide quasicrystal on Pd(111) — •Martin Haller, Sebastian Schenk, Stefan Förster, and Wolf Widdra — Martin-Luther-Universität Halle-Wittenberg, 06120 Halle, Germany

Oxide quasicrystals (OQCs) are 2D oxide films with dodecagonal symmetry grown on a hexagonal metal substrate. The dodecagonal symmetry results from a square-triangle-rhombus tiling of alkaline earth atoms, as Ba or Sr, in a Ti-O network [1]. Europium has a comparable ionic radius as Sr and the same 2+ oxidation state and is an interesting OQC substituent due to its half-filled 4f shell resulting in a strong magnetic moment. Here, we show that an OQC forms by Eu deposition onto a Ti-O network on Pd(111) and subsequent annealing. We analyze the Eu-Ti-O OQC and compare it with the prototypical Ba-Ti-O system based on LEED and STM data. From LEED, we deduce a reduction of the characteristic length scale and a close match with the theoretical diffraction pattern. In real space, the tiling frequencies are found to be 2.80:1:0.38 for squares:triangles:rhombi. Those are in good agreement to the ideal ratio of 2.73:1:0.37 [2]. Lastly, we analyze the datasets in hyperspace, where we observe the typical confinement of the projected points inside the dodecagonal acceptance domain.
[1] Schenk et al., Nature Communications, 13, 7542 (2022)
[2] Schenk et al., Acta Crystallographica A, 75, 307 (2019)

Keywords: quasicrystals; europium; oxide surfaces; STM; LEED

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