Dresden 2017 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 67: Perovskites, Hybrid Photovoltaics and Plasmonics

HL 67.5: Invited Talk

Thursday, March 23, 2017, 10:45–11:15, POT 81

2D Quasicrystals from Semiconducting Perovskite Oxides — •Wolf Widdra^1,2 and Stefan Förster¹ — ¹Martin-Luther-Universität Halle-Wittenberg, Halle, Germany — ²Max-Planck-Institut für Mikrostrukturphysik, Halle, Germany

During the last decade, the fields of interface-driven 2D materials have gained tremendous attention, often due to their promising new structural or advantageous transport properties. One of these are the interface-driven 2D oxide quasicrystals (OQCs) which exhibit perfect, long-range dodecagonal rotational symmetry [1]. Such symmetry is forbidden for periodic structures. However, it can form in systems that are describable by 2D tiling patterns, which follow self-similarity supporting inflation rules. For the class of Perovskite oxides, we show that ultrathin films restructure into 2D quasicrystals on top of a threefold metallic substrate: BaTiO₃ as well as SrTiO₃ form stable and long-range ordered dodecagonal OQCs on Pt(111) that are characterized by brilliant 12-fold diffraction patterns [1]. Scanning tunneling microscopy resolves the aperiodic structure of surface atoms forming tiling patterns based on triangular, quadratic, and rhombic elements that are self-similar on length scales of (2+√3)ⁿ times 0.68 nm. Concept and details of the interface-driven structures will be discussed in context of phason strain and formation of competing approximant structures [2]. First results on the electronic bandstructure will be presented.

[1] S. Förster et al., Nature 502, 215 (2013). [2] S. Förster et al., Phys. Rev. Lett. 117, 095501 (2016).