Abstract
The microstructure and valence states of three single crystal thin film systems, UO 2 on (11̄02) r-plane sapphire, UO 2 on (001) yttria-stabilized zirconia, and U 3O 8 on (11̄02) r-plane sapphire, grown via reactive-gas magnetron sputtering are analyzed primarily with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS). XRD analysis indicates the growth of single crystal domains with varying degrees of mosaicity. XPS and UPS analyses yield U-4f, U-5f, O-1s, and O-2p electron binding energies consistent with reported bulk values. A change from p-type to n-type semiconductor behavior induced by preferential sputtering of oxygen during depth profile analysis was observed with both XPS and UPS. Trivalent cation impurities (Nd and Al) in UO 2 lower the Fermi level, shifting the XPS spectral weight. This observation is consistent with hole-doping of a Mott-Hubbard insulator. The uranium oxide-(11̄02) sapphire system is unstable with respect to Al interdiffusion across the film-substrate interface at elevated temperature.
Original language | English (US) |
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Pages (from-to) | 5616-5626 |
Number of pages | 11 |
Journal | Thin Solid Films |
Volume | 520 |
Issue number | 17 |
DOIs | |
State | Published - Jun 30 2012 |
Keywords
- Cation impurity
- Magnetron sputtering
- Microstructure
- Thin films
- Uranium oxide
- Valence
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Metals and Alloys
- Materials Chemistry