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O: Fachverband Oberflächenphysik

O 74: Poster Session VI: Oxide and insulator surfaces: Structure, epitaxy and growth II

O 74.1: Poster

Mittwoch, 3. März 2021, 13:30–15:30, P

Reduction of the α-Fe₂O₃(1102) surface to Fe₃O₄ — •Erik Rheinfrank¹, Giada Franceschi¹, Igor Sokolović¹, Jesús Redondo², Pavel Procházka³, Nishant Kumar³, Ondřej Man³, Jan Michalička³, Jan Čechal³, Michael Schmid¹, Gareth S. Parkinson¹, Ulrike Diebold¹, and Michele Riva¹ — ¹Institute of Applied Physics, TU Wien, Austria — ²Charles University, Faculty of Mathematics and Physics, Prague, Czech Republic — ³CEITEC, Brno, Czech Republic

Iron oxides list among the most abundant compounds in Earth’s crust and are involved in many natural processes as well as in a wide range of applications. To understand their fundamental surface-chemical properties it is crucial to reproducibly prepare atomically well-defined surfaces in a controlled environment. Here we report on the local reduction of the α-Fe₂O₃(1102) surface by two processes. First, by annealing in ultra high vacuum (UHV) at 450 ^∘C and subsequent sputtering and annealing in low 10⁻⁶ mbar O₂ at 450 ^∘C, and second, by annealing in UHV at 600 ^∘C. Atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) reveal that both routes lead to the formation of boulder-like magnetite inclusions. Once they are created, the preferential removal of oxygen by sputtering enhances their formation instead of removing them. A pristine hematite surface can be recovered by exposure to higher oxygen pressures (1 mbar) at ∼ 850^∘C. The nature of these Fe₃O₄ inclusions was studied by low-energy electron microscopy (LEEM) and low-energy electron diffraction (LEED).