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

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• 作者：Melissa M. Strehle ; Brent J. Heuser ; ^{bheuser@illinois.edu} ; Mohamed S. Elbakhshwan ; Xiaochun Han ; David J. Gennardo ; Harrison K. Pappas ; Hyunsu Ju
• 关键词：Uranium oxide ; Magnetron sputtering ; Microstructure ; Thin films ; Valence ; Cation impurity
• 刊名：Thin Solid Films
• 出版年：2012
• 期刊代码：78_00406090
• 类别：ph
• 出版时间：30 June, 2012
• 卷：520
• 期：17
• 页码：5616-5626
• 文件大小：1198 K

摘要

The microstructure and valence states of three single crystal thin film systems, UO₂ on (102) r-plane sapphire, UO₂ on (001) yttria-stabilized zirconia, and U₃O₈ on (102) 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 UO₂ lower the Fermi level, shifting the XPS spectral weight. This observation is consistent with hole-doping of a Mott-Hubbard insulator. The uranium oxide-(102) sapphire system is unstable with respect to Al interdiffusion across the film-substrate interface at elevated temperature.