Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 65: Focus Session: Structure and Chemistry of Metal-Oxide Surfaces III

O 65.3: Hauptvortrag

Mittwoch, 14. März 2018, 15:30–16:00, MA 005

Bulk-terminated surfaces of KTaO₃ and SrTiO₃ studied by combined STM/AFM — •Martin Setvin — TU Wien

Recent development of the noncontact atomic force microscopy (nc-AFM) has opened new possibilities in different fields - imaging of organic molecules [1], controlling the charge state of adsorbed species [2], or measuring forces involved in a single chemical bond [3]. I will focus on the possibilities and opportunities emerging on oxide surfaces. The limits of atomic resolution will be illustrated on clean and water-exposed binary oxides like TiO₂ or In₂O₃. The technique opens new ways towards investigation of complex oxides; this will be illustrated on the (001) surfaces of cubic perovskites KTaO₃ and SrTiO₃. These materials, when prepared by cleaving, consist of a mixture of two terminations (KO/TaO₂, SrO/TiO₂). The layout of these terminations resembles the shape of ferroelectric domains, indicating that the incipient-ferroelectric character of these materials can be used for tuning the surface topography. Basic physical and chemical properties of these surfaces will be discussed, with a special focus on the polar KTaO₃ (001) surface. This surface compensates its inherent instability by various mechanisms like formation of 2DEG-like states in the band gap, ferroelectricity, point defects, surface restructuring, or adsorbate-induced reconstruction. Tuning the environment allows choosing which mechanism will be in play and controlling the surface termination.

[1] L. Gross et al., Science 2009, 325, 1110 [2] L. Gross et al., Science 2009, 324, 1428 [3] Y. Sugimoto et al., Nature 2007, 446, 64