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O: Fachverband Oberflächenphysik

O 61: Poster Session V: Oxide and insulator surfaces: Structure, epitaxy and growth I

O 61.7: Poster

Wednesday, March 3, 2021, 10:30–12:30, P

Subtle differences between periodic and aperiodic 2D ternary oxides determined from photoemission spectroscopy — •Loi Vinh Tran, Maniraj Mahalingam, Oliver Krahn, Stefan Förster, and Wolf Widdra — Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany

The discovery of oxide quasicrystals (OQCs) in two-dimensional ternary oxides on metal support has triggered many studies in this field in recent years [1,2]. Here, for the first time, the single-phase preparations of approximants in a periodic hexagonal wagon-wheel structure (WW) and a six-membered ring (6Net) network structure are reported, which are known from mixed phases [3]. This enables a side-by-side comparison between the aperiodic OQC and two distinct periodic superstructures of the same material by means of X-ray, UV photoemission spectroscopy (XPS, UPS). These periodic structures together with the OQC system are distinguished in terms of stoichiometry, workfunction, and atomic density measured by XPS, UPS and STM. Changes in workfunctions from 3.8, via 4.0, to 4.2 eV for the OQC, WW, and 6Net structures, respectively, are observed. On the other hand, XPS reveals a decreasing Ba:Ti ratio for the same sequence of structures as well as the atomic density measured by STM. The implications of these observations on different structural properties of BaTiO3 will be discussed.