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O: Fachverband Oberflächenphysik
O 61: Poster Session V: Oxide and insulator surfaces: Structure, epitaxy and growth I
O 61.6: Poster
Wednesday, March 3, 2021, 10:30–12:30, P
A Large Unit Cell Quasicrystal Approximant derived from SrTiO3 on Pt(111): A LEED, STM and STS Study — •Oliver Krahn, Sebastian Schenk, Stefan Förster, and Wolf Widdra — Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
The discovery of a two-dimensional dodecagonal oxide quasicrystal (OQC) formed from BaTiO3 on Pt(111) has pushed the field of ultrathin ternary oxides on metal supports [1]. The OQC structure is based on atomic arrangements in vertices of triangles, squares and rhombuses. Periodically repeated patches of the OQC tiling are known as approximants. In this contribution, we present the largest approximant observed so far, emerging in ultrathin SrTiO3 on Pt(111), homogenously covering the entire substrate surface. As derived from low-temperature scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED), its unit cell spans an area of (44 × 43)Å2. Inside the unit cell, 48 Ti atoms are seen by STM, which form the vertices of 48 triangles, 18 squares and 6 rhombuses. Interestingly, this structure can be understood as a unit cell doubling of a previously reported approximant resulting from a glide mirror symmetry [2]. Detailed studies of the electronic structure by scanning tunneling spectroscopy (STS) reveal the metallic behaviour of the film around the Fermi energy and the independence of the local electronic structure from different vertex configurations in the unoccupied states regime.
[1] S. Förster, O. Krahn et al., Phys. Status Solidi B 257, 1900624 (2020)
[2] S. Schenk et al., J. Phys.: Condens. Matter 29, 134002 (2017)