Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 43: Clean surfaces III

O 43.5: Talk

Wednesday, March 28, 2012, 11:30–11:45, MA 043

Fe-rich terminations and the role of subsurface charge order at the Fe₃O₄(001) surface — •Zbynek Novotny, Gareth S. Parkinson, Zoltan Edes, Michael Schmid, and Urlike Diebold — Institute of Applied Physics, TU Wien, Vienna, Austria

Magnetite, Fe₃O₄, crystallizes in the inverse spinel structure with an fcc oxygen sublattice and Fe cations in tetrahedral (A) and octahedral (B) sites. The (001) surface exhibits undulating rows of Fe(B) atoms with two unoccupied Fe(A) bulk continuation sites in the ’narrow’ and ’wide’ regions of the unit cell, related to Fe²⁺/Fe³⁺ subsurface charge ordering [1,2]. We present a route to produce a reduced, well-ordered Fe₃O₄(001) surface by evaporating Fe on the distorted Fe(B) surface at room temperature. STM shows that this surface contains Fe(A) monomers and Fe clusters. Mild annealing of the sample leads to a surface containing Fe(A) monomers and, with increasing Fe coverage, dimers of 5-fold coordinated Fe. Both surfaces contain Fe adatoms located at the ’narrow’ position within the unit cell, indicating a strong preference for sites located above Fe²⁺ cations in the subsurface layer.

This material is based upon work supported as part of the Center for Atomic-Level Catalyst Design, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number #DE-SC0001058.

[1] R. Pentcheva et al., Phys. Rev. Lett. 94, 126101 (2005).
[2] Z. Łodziana, Phys. Rev. Lett. 99, 206402 (2007).