Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 27: Metal Oxide Surfaces I: Structure, Epitaxy and Growth
O 27.7: Vortrag
Dienstag, 2. April 2019, 12:15–12:30, H16
Surface structure of Ti-doped Hematite α-Fe2O3 films grown by pulsed laser deposition — •Florian Kraushofer, Giada Franceschi, Zdenek Jakub, Magdalena Bichler, Michele Riva, Michael Schmid, Ulrike Diebold, Peter Blaha, and Gareth S. Parkinson — TU Wien, 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.
One widespread strategy for improving the electrocatalytic behavior of hematite anodes is to dope them slightly with titanium. However, the resulting performance usually scales with the doping level in a non-trivial way, suggesting multiple competing effects, such as independent modification of bulk conductivity and surface reactivity. How the hematite surface is modified by the presence of titanium has not been explored in depth.
Here we present an atomic-scale scanning tunneling microscopy (STM) study of Ti-doped hematite films, grown homoepitaxially on undoped hematite single crystals by pulsed laser deposition. We show that on hematite (1102), titanium substitutes iron in the surface layer to form areas of an ilmenite-type FeTiO3 termination even at low bulk doping levels, suggesting preferential agglomeration in the surface. For comparison, titanium was also deposited directly on an undoped hematite sample, which yields the same surface modification after annealing.