Regensburg 2025 – scientific programme

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DS: Fachverband Dünne Schichten

DS 5: Thin Oxides and Oxide Layers

DS 5.1: Talk

Tuesday, March 18, 2025, 14:00–14:15, H3

How to functionalize 2D states at oxide interfaces by controlled redox reaction — •Pia Maria Düring, Andreas Fuhrberg, Timo Krieg, Verena Reva, and Martina Müller — FB Physik, Universität Konstanz, 78457 Konstanz

Oxide electronics provide the key concepts and materials for enhancing silicon-based semiconductor technologies with novel functionalities. In a recent paper, we provide evidence for individually emerging hole- and electron-type 2D band dispersions at Fe-SrTiO₃ heterostructures [1]. The emergence of p- or n-type bands is closely linked to the Fe oxidation state which enables the possibility to tune the interface properties to set or even switch between negatively (n) charged electrons or positively (p) charged holes. One of the main processes that controls the interface properties is the oxygen exchange between the film and the substrate. Using our UHV-MBE system, we grow high-quality ultrathin TM (e.g. Fe, Co and Hf) oxide films on SrTiO₃ substrates by systematically varying the growth parameters, e.g. (i) growth temperature, (ii) substrate annealing, and (iii) metal film thickness. The present work discusses the effect of different growth parameters on the interfacial properties like oxygen vacancies, the oxidation state of the TM oxide as well as the concentration of defects in SrTiO₃, which strongly influences the valence band alignment between electron and hole band bending. In this way, we can effectively control the properties of the 2D interface to ultimately add ferroic functionalities to these confined electronic states.

[1] P. M. Düring et al., Advanced Materials, 2024, 2390217.

Keywords: Oxide Interfaces; Photoelectron Spectroscopy; MBE; 2DEG; XPS