Characterization of single crystal uranium-oxide thin films grown via reactive-gas magnetron sputtering on yttria-stabilized zirconia and sapphire

Melissa M. Strehle, Brent J. Heuser, Mohamed S. Elbakhshwan, Xiaochun Han, David J. Gennardo, Harrison K. Pappas, Hyunsu Ju

Research output: Contribution to journalArticlepeer-review

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 languageEnglish (US)
Pages (from-to)5616-5626
Number of pages11
JournalThin Solid Films
Volume520
Issue number17
DOIs
StatePublished - 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

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