Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 55: Focus Session: Structure and Chemistry of Metal-Oxide Surfaces II
O 55.5: Talk
Wednesday, March 14, 2018, 11:30–11:45, MA 005
Direct detection of Ni adatoms being driven subsurface on Fe3O4(001) — •Paul T. P. Ryan1,2, Zdeněk Jakub3, Jan Balajka3, Jan Hulva3, Roland Bliem3, Pardeep K. Thakur2, Tien-Lin Lee2, Francesco Allegretti4, David J. Payne1, David A. Duncan2, and Gareth S. Parkinson3 — 1Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ — 2Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0QX UK — 3Institute of Applied Physics, TU Wien, 1040 Vienna, Austria — 4Physics Department E20, Technical University of Munich, 85748 Garching, Germany
Iron oxides are the archetypal cation defect material. For magnetite (Fe3O4) these cation vacancies can play an important role in its surface chemistries. Specifically, Fe3O4 has been observed to pattern the adsorption of a wide range of metal adatoms onto its (001) surface, where two sub-surface octahedral vacancies and one surface tetrahedral interstitial kinetically hinder the sintering of metal adatoms into nanoparticles. Despite this, STM observations of several first row transition metals, e.g. Ni and Co, suggest that these adatoms can be thermally driven into the subsurface octahedral vacancies [1]. Here we present an X-ray standing wave (XSW) study directly demonstrating the co-existence of Ni in a surface tetrahedral site, a subsurface octahedral site and a bulk octahedral site confirming the interpretation of previous STM measurements and quantitatively probing the vertical displacement of the Ni atoms at each location.
[1] R. Bliem, et al. Phys. Rev. B, 92 (2015) 075440