期刊
SURFACE SCIENCE
卷 603, 期 2, 页码 291-297出版社
ELSEVIER
DOI: 10.1016/j.susc.2008.11.022
关键词
Co3O4; Spinel; Interface structure; Polar surfaces; Surface termination
资金
- NSF [0520495, 0705799]
- ONR
- Petroleum Research Foundation [42178AC5, 42259-AC5]
- DOE Catalysis and Chemical Transformations Program [DE-FG02-06ER15834]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [0520495] Funding Source: National Science Foundation
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [0705799] Funding Source: National Science Foundation
The interface and electronic structure of thin (similar to 20-74 nm) Co3O4(110) epitaxial films grown by oxygen-assisted molecular beam epitaxy on MgAl2O4(110) single crystal substrates have been investigated by means of real and reciprocal space techniques. As-grown film surfaces are found to be relatively disordered and exhibit an oblique low energy electron diffraction (LEED) pattern associated with the O-rich CoO2 bulk termination of the (110) surface. Interface and bulk film structure are found to improve significantly with post-growth annealing at 820 K in air and display sharp rectangular LEED patterns, suggesting a surface stoichiometry of the alternative Co2O2 bulk termination of the (110) surface. Non-contact atomic force microscopy demonstrates the presence of wide terraces separated by atomic steps in the annealed films that are not present in the as-grown structures; the step height of approximate to 2.7 angstrom corresponds to two atomic layers and confirms a single termination for the annealed films, consistent with the LEED results. A model of the (1 x 1) surfaces that allows for compensation of the polar surfaces is presented. (C) 2008 Elsevier B.V. All rights reserved.
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