[Zurück]

E. Rheinfrank, G. Franceschi, I. Sokolovic, J. Redondo, P. Procházka, N. Kumar, O. Man, J. Michalička, J. Čechal, M. Schmid, G. Parkinson, U. Diebold, M. Riva:
"Reduction of the α-Fe₂O₃(1102) surface to Fe₃O₄";
Poster: DPG-Frühjahrstagung (DPG Spring Meeting) of the Surface Science Division, SurfaceScience21, virtual; 03.03.2021.

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).