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O: Fachverband Oberflächenphysik
O 6: Oxides and Insulator Surfaces: Structure, Epitaxy and Growth
O 6.5: Vortrag
Montag, 17. März 2025, 11:30–11:45, H8
Segregation Effects in 2D Mixed Oxide Nano-Islands: Edge Structure and Composition in Mixed V-Fe Oxide Monolayers — Ying Wang1, Piotr Igor Wemhoff1, Ghada Missaoui1, •Niklas Nilius1, Jacek Goniakowski2, and Claudine Noguera2 — 1Carl von Ossietzky University, Institute of Physics, D-26111 Oldenburg, Germany — 2CNRS-Sorbonne University, UMR 7588, INSP, F-75005 Paris, France
Low-coordinated atoms residing at the edges of oxide nanostructures play an important role in heterogenous catalysis. Their local configuration is however hardly available, especially for ternary materials with variable stoichiometry. In this study, low-temperature STM is employed to analyze the edge configurations of V-Fe-O honeycomb islands grown on Pt(111) as a function of film composition. The islands are delimited by zigzag and armchair edges, the latter with a tendency to reconstruct into sequences of four, five, six and seven-membered rings. STM spectroscopy is used to identify the chemical nature of the edge atoms. The thermodynamic forces for V or Fe segregation to the edges, both oxygen and cation terminated, are analyzed by DFT calculations. In an oxidizing environment, formation of vanadyl-terminated (VO-) edges is energetically favorable, while Fe atoms segregate towards the edges at O-poor conditions. The observed behavior is explained by the higher oxygen affinity of V versus Fe edge cations, and reflected in the higher stability of terminal vanadyl compared to ferryl groups. Our findings indicate a new pathway to tailor the chemical composition and catalytic reactivity of oxide edges via cationic mixing.
Keywords: Ternary oxides; 2D islands; Edge configuration; Scanning tunneling microscopy; Density functional theory