Structural and Optical Properties of Phase-Pure UO2, α-U3O8, and α-UO3Epitaxial Thin Films Grown by Pulsed Laser Deposition

Erik Enriquez; Gaoxue Wang; Yogesh Sharma; Ibrahim Sarpkaya; Qiang Wang; Di Chen; Nicholas Winner; Xiaofeng Guo; John Dunwoody; Joshua White; Andrew Nelson; Hongwu Xu; Paul Dowden; Enrique Batista; Han Htoon; Ping Yang; Quanxi Jia; Aiping Chen

doi:10.1021/acsami.0c08635

Structural and Optical Properties of Phase-Pure UO₂, α-U₃O₈, and α-UO₃Epitaxial Thin Films Grown by Pulsed Laser Deposition

Erik Enriquez, Gaoxue Wang, Yogesh Sharma, Ibrahim Sarpkaya, Qiang Wang, Di Chen, Nicholas Winner, Xiaofeng Guo, John Dunwoody, Joshua White, Andrew Nelson, Hongwu Xu, Paul Dowden, Enrique Batista, Han Htoon, Ping Yang, Quanxi Jia, Aiping Chen

Research output: Contribution to journal › Article › peer-review

33 Scopus citations

Abstract

Fundamental understanding of the electronic, chemical, and structural properties of uranium oxides requires the synthesis of high-crystalline-quality epitaxial films of different polymorphs of one material or different phases with various oxygen valence states. We report the growth of single-phase epitaxial UO2, α-U3O8, and α-UO3 thin films using pulsed laser deposition. Both oxygen partial pressure and substrate temperature play critical roles in determining the crystal structure of the uranium oxide films. X-ray diffraction and Raman spectroscopy demonstrate that the films are single phase with excellent crystallinity and epitaxially grown on a variety of substrates. Chemical valance states and optical properties of epitaxial uranium oxide films are studied by X-ray photoelectron spectroscopy and UV-vis spectroscopy, which further confirm the high-quality stoichiometric phase-pure uranium oxide thin films. Epitaxial UO2 films show a direct band gap of 2.61 eV, while epitaxial α-U3O8 and α-UO3 films exhibit indirect band gaps of 1.89 and 2.26 eV, respectively. The ability to grow high-quality epitaxy actinide oxide thin films and to access their different phases and polymorphous will have significant benefits to the future applications in nuclear science and technology.

Original language	English
Pages (from-to)	35232-35241
Number of pages	10
Journal	ACS Applied Materials and Interfaces
Volume	12
Issue number	31
DOIs	https://doi.org/10.1021/acsami.0c08635
State	Published - Aug 5 2020
Externally published	Yes

Funding

The work at Los Alamos National Laboratory (LANL) was supported by the NNSA’s Laboratory Directed Research and Development Program and was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy Office of Science. Los Alamos National Laboratory, an affirmative action equal opportunity employer, is managed by Triad National Security, LLC, for the U.S. Department of Energy’s NNSA, under contract 89233218CNA000001. The DFT + U calculations were performed using EMSL (grid.436923.9), a DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research. Y.S. acknowledges the support from the G. T. Seaborg Institute at LANL.

Keywords

epitaxial stabilization
optical properties
thin films
uranium oxides

Access to Document

10.1021/acsami.0c08635

Cite this

Enriquez, E., Wang, G., Sharma, Y., Sarpkaya, I., Wang, Q., Chen, D., Winner, N., Guo, X., Dunwoody, J., White, J., Nelson, A., Xu, H., Dowden, P., Batista, E., Htoon, H., Yang, P., Jia, Q., & Chen, A. (2020). Structural and Optical Properties of Phase-Pure UO₂, α-U₃O₈, and α-UO₃Epitaxial Thin Films Grown by Pulsed Laser Deposition. ACS Applied Materials and Interfaces, 12(31), 35232-35241. https://doi.org/10.1021/acsami.0c08635

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abstract = "Fundamental understanding of the electronic, chemical, and structural properties of uranium oxides requires the synthesis of high-crystalline-quality epitaxial films of different polymorphs of one material or different phases with various oxygen valence states. We report the growth of single-phase epitaxial UO2, α-U3O8, and α-UO3 thin films using pulsed laser deposition. Both oxygen partial pressure and substrate temperature play critical roles in determining the crystal structure of the uranium oxide films. X-ray diffraction and Raman spectroscopy demonstrate that the films are single phase with excellent crystallinity and epitaxially grown on a variety of substrates. Chemical valance states and optical properties of epitaxial uranium oxide films are studied by X-ray photoelectron spectroscopy and UV-vis spectroscopy, which further confirm the high-quality stoichiometric phase-pure uranium oxide thin films. Epitaxial UO2 films show a direct band gap of 2.61 eV, while epitaxial α-U3O8 and α-UO3 films exhibit indirect band gaps of 1.89 and 2.26 eV, respectively. The ability to grow high-quality epitaxy actinide oxide thin films and to access their different phases and polymorphous will have significant benefits to the future applications in nuclear science and technology.",

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Enriquez, E, Wang, G, Sharma, Y, Sarpkaya, I, Wang, Q, Chen, D, Winner, N, Guo, X, Dunwoody, J, White, J, Nelson, A, Xu, H, Dowden, P, Batista, E, Htoon, H, Yang, P, Jia, Q & Chen, A 2020, 'Structural and Optical Properties of Phase-Pure UO₂, α-U₃O₈, and α-UO₃Epitaxial Thin Films Grown by Pulsed Laser Deposition', ACS Applied Materials and Interfaces, vol. 12, no. 31, pp. 35232-35241. https://doi.org/10.1021/acsami.0c08635

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AU - Enriquez, Erik

AU - Wang, Gaoxue

AU - Sharma, Yogesh

AU - Sarpkaya, Ibrahim

AU - Wang, Qiang

AU - Chen, Di

AU - Winner, Nicholas

AU - Guo, Xiaofeng

AU - Dunwoody, John

AU - White, Joshua

AU - Nelson, Andrew

AU - Xu, Hongwu

AU - Dowden, Paul

AU - Batista, Enrique

AU - Htoon, Han

AU - Yang, Ping

AU - Jia, Quanxi

AU - Chen, Aiping

PY - 2020/8/5

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N2 - Fundamental understanding of the electronic, chemical, and structural properties of uranium oxides requires the synthesis of high-crystalline-quality epitaxial films of different polymorphs of one material or different phases with various oxygen valence states. We report the growth of single-phase epitaxial UO2, α-U3O8, and α-UO3 thin films using pulsed laser deposition. Both oxygen partial pressure and substrate temperature play critical roles in determining the crystal structure of the uranium oxide films. X-ray diffraction and Raman spectroscopy demonstrate that the films are single phase with excellent crystallinity and epitaxially grown on a variety of substrates. Chemical valance states and optical properties of epitaxial uranium oxide films are studied by X-ray photoelectron spectroscopy and UV-vis spectroscopy, which further confirm the high-quality stoichiometric phase-pure uranium oxide thin films. Epitaxial UO2 films show a direct band gap of 2.61 eV, while epitaxial α-U3O8 and α-UO3 films exhibit indirect band gaps of 1.89 and 2.26 eV, respectively. The ability to grow high-quality epitaxy actinide oxide thin films and to access their different phases and polymorphous will have significant benefits to the future applications in nuclear science and technology.

AB - Fundamental understanding of the electronic, chemical, and structural properties of uranium oxides requires the synthesis of high-crystalline-quality epitaxial films of different polymorphs of one material or different phases with various oxygen valence states. We report the growth of single-phase epitaxial UO2, α-U3O8, and α-UO3 thin films using pulsed laser deposition. Both oxygen partial pressure and substrate temperature play critical roles in determining the crystal structure of the uranium oxide films. X-ray diffraction and Raman spectroscopy demonstrate that the films are single phase with excellent crystallinity and epitaxially grown on a variety of substrates. Chemical valance states and optical properties of epitaxial uranium oxide films are studied by X-ray photoelectron spectroscopy and UV-vis spectroscopy, which further confirm the high-quality stoichiometric phase-pure uranium oxide thin films. Epitaxial UO2 films show a direct band gap of 2.61 eV, while epitaxial α-U3O8 and α-UO3 films exhibit indirect band gaps of 1.89 and 2.26 eV, respectively. The ability to grow high-quality epitaxy actinide oxide thin films and to access their different phases and polymorphous will have significant benefits to the future applications in nuclear science and technology.

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