L18
L.R. Merte et al. / Surface Science 603 (2009) L15–L18
Partial reduction of the surface thus allows oxygen atoms, at the cen-
ter of small triangles and the corners of large triangles, to shift from
less favorable sites above Pt atoms to more favorable hollow sites,
converting HCP domains to FCC* domains and yielding an energy
gain on the order of 0.1-0.2 eV per FeO unit.
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Similar trends in structural stability are to be expected for all
moiré-structured oxide films, suggesting that our method may find
application beyond the FeO(111)/Pt(111) system. Indeed, we ob-
serve similar dislocations upon reduction of FeO films grown on
Pd(111) and Au(111). In addition to their use as nanotemplates
for the bottom-up assembly of regular arrays of nanostructures,
these oxide films may serve as useful models for low-temperature
oxidation catalysts, as noble metals in close contact with iron oxi-
des have been shown to have high activities [25–27]. In such noble
metal/reducible oxide catalysts, the oxide is believed to play a di-
rect role in the catalytic mechanism. A promising approach to the
study of these types of catalysts is the use of thin oxide films and
nanostructures grown on flat metal substrates as model systems
[28,29]. One of the main advantages of this method is that it sim-
plifies atomic-scale imaging and allows detailed characterization
of the metal/metal oxide interface and its physical and chemical
properties. Application of FeO films as model catalysts will require
accurate interpretation of STM images, the basis for which is pro-
vided by our work.
In conclusion, we have presented a new approach by which the
STM images and their relation to the atomic-scale structure of an
FeO thin film can be interpreted unambiguously. Our results devi-
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of the properties of the FeO film and emphasizing the need for
experimental corroboration of theoretical results. The novel ap-
proach presented here should be generally applicable for the deter-
mination of the atomic-scale structure of many other thin epitaxial
oxide films.
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Work at UW was supported by DOE-BES, Chemical Sciences
Division. Supercomputing time was utilized at NERSC, PNNL, and
ORNL.