Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 24: Focus Session: Structure and Chemistry of Metal-Oxide Surfaces I

O 24.3: Talk

Tuesday, March 13, 2018, 11:15–11:30, MA 005

Atomic-scale structure of the Hematite α-Fe2O3(1-102) surface — •Florian Kraushofer, Zdenek Jakub, Magdalena Bichler, Jan Hulva, Martin Setvin, Michael Schmid, Ulrike Diebold, Peter Blaha, and Gareth S. Parkinson — Vienna University of Technology, Vienna, Austria

Hematite (α-Fe2O3) is a promising material for technological applications due to its abundance, low cost and chemical stability. Its 2.2 eV bandgap makes it potentially ideal as a photoanode for photoelectrochemical water splitting, but performance is hampered by slow reaction kinetics and the need for a significant overpotential.

To date, most surface science studies of α-Fe2O3 have focused on the (0001) facet, but preparing a stoichiometric surface under UHV conditions has proven problematic. Some authors have investigated the equally relevant (1-102) surface, and reported that a (1x1) and a reduced (2x1) termination can be reversibly prepared. Several models have been proposed for the (2x1) reconstruction, but as of now no scanning probe data exists to support or refute them.

Here we present an atomic-scale scanning tunnelling microscopy (STM) study of the (1x1) and (2x1) surfaces of α-Fe2O3 (1-102). The data acquired for the (1x1) termination support a bulk termination model, as predicted by previous publications, but STM and nc-AFM images of the (2x1) reconstruction are inconsistent with previously proposed models. We propose a new model based on ordered oxygen vacancies, the plausibility of which is confirmed by density functional theory (DFT) results.