Identification of electron and hole traps in lithium tetraborate (Li 2B4O7) crystals: Oxygen vacancies and lithium vacancies

M. W. Swinney; J. W. McClory; J. C. Petrosky; Shan Yang; A. T. Brant; V. T. Adamiv; Ya V. Burak; P. A. Dowben; L. E. Halliburton

doi:10.1063/1.3392802

Identification of electron and hole traps in lithium tetraborate (Li ₂B₄O₇) crystals: Oxygen vacancies and lithium vacancies

M. W. Swinney, J. W. McClory, J. C. Petrosky, Shan Yang, A. T. Brant, V. T. Adamiv, Ya V. Burak, P. A. Dowben, L. E. Halliburton

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51 Scopus citations

Abstract

Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify and characterize electrons trapped by oxygen vacancies and holes trapped by lithium vacancies in lithium tetraborate (Li ₂B₄O₇) crystals. Our study includes a crystal with the natural abundances of ¹⁰B and ¹¹B and a crystal highly enriched with ¹⁰B. The as-grown crystals contain isolated oxygen vacancies, lithium vacancies, and copper impurities, all in nonparamagnetic charge states. During an irradiation at 77 K with 60 kV x-rays, doubly ionized oxygen vacancies trap electrons while singly ionized lithium vacancies and monovalent copper impurities trap holes. The vacancies return to their preirradiation charge states when the temperature of the sample is increased to approximately 90 K. Hyperfine interactions with ¹⁰B and ¹¹B nuclei, observed between 13 and 40 K in the radiation-induced EPR and ENDOR spectra, provide models for the two vacancy-related defects. The electron trapped by an oxygen vacancy is localized primarily on only one of the two neighboring boron ions while the hole stabilized by a lithium vacancy is localized on a neighboring oxygen ion with nearly equal interactions with the two boron ions adjacent to the oxygen ion.

Original language	English
Article number	113715
Journal	Journal of Applied Physics
Volume	107
Issue number	11
DOIs	https://doi.org/10.1063/1.3392802
State	Published - Jun 1 2010
Externally published	Yes

Funding

This work was supported at the Air Force Institute of Technology by Grant Nos. HDTRA1-07-1-0008 and BRBAA08-I-2-0128 from the Defense Threat Reduction Agency and at West Virginia University by Grant No. DMR-0804352 from the National Science Foundation. The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Air Force, the Department of Defense, or the United States Government.

Funders	Funder number
National Science Foundation
Defense Threat Reduction Agency
West Virginia University	DMR-0804352
Air Force Institute of Technology	BRBAA08-I-2-0128, HDTRA1-07-1-0008

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title = "Identification of electron and hole traps in lithium tetraborate (Li 2B4O7) crystals: Oxygen vacancies and lithium vacancies",

abstract = "Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify and characterize electrons trapped by oxygen vacancies and holes trapped by lithium vacancies in lithium tetraborate (Li 2B4O7) crystals. Our study includes a crystal with the natural abundances of 10B and 11B and a crystal highly enriched with 10B. The as-grown crystals contain isolated oxygen vacancies, lithium vacancies, and copper impurities, all in nonparamagnetic charge states. During an irradiation at 77 K with 60 kV x-rays, doubly ionized oxygen vacancies trap electrons while singly ionized lithium vacancies and monovalent copper impurities trap holes. The vacancies return to their preirradiation charge states when the temperature of the sample is increased to approximately 90 K. Hyperfine interactions with 10B and 11B nuclei, observed between 13 and 40 K in the radiation-induced EPR and ENDOR spectra, provide models for the two vacancy-related defects. The electron trapped by an oxygen vacancy is localized primarily on only one of the two neighboring boron ions while the hole stabilized by a lithium vacancy is localized on a neighboring oxygen ion with nearly equal interactions with the two boron ions adjacent to the oxygen ion.",

author = "Swinney, {M. W.} and McClory, {J. W.} and Petrosky, {J. C.} and Shan Yang and Brant, {A. T.} and Adamiv, {V. T.} and Burak, {Ya V.} and Dowben, {P. A.} and Halliburton, {L. E.}",

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AU - Swinney, M. W.

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AU - Petrosky, J. C.

AU - Yang, Shan

AU - Brant, A. T.

AU - Adamiv, V. T.

AU - Burak, Ya V.

AU - Dowben, P. A.

AU - Halliburton, L. E.

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N2 - Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify and characterize electrons trapped by oxygen vacancies and holes trapped by lithium vacancies in lithium tetraborate (Li 2B4O7) crystals. Our study includes a crystal with the natural abundances of 10B and 11B and a crystal highly enriched with 10B. The as-grown crystals contain isolated oxygen vacancies, lithium vacancies, and copper impurities, all in nonparamagnetic charge states. During an irradiation at 77 K with 60 kV x-rays, doubly ionized oxygen vacancies trap electrons while singly ionized lithium vacancies and monovalent copper impurities trap holes. The vacancies return to their preirradiation charge states when the temperature of the sample is increased to approximately 90 K. Hyperfine interactions with 10B and 11B nuclei, observed between 13 and 40 K in the radiation-induced EPR and ENDOR spectra, provide models for the two vacancy-related defects. The electron trapped by an oxygen vacancy is localized primarily on only one of the two neighboring boron ions while the hole stabilized by a lithium vacancy is localized on a neighboring oxygen ion with nearly equal interactions with the two boron ions adjacent to the oxygen ion.

AB - Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify and characterize electrons trapped by oxygen vacancies and holes trapped by lithium vacancies in lithium tetraborate (Li 2B4O7) crystals. Our study includes a crystal with the natural abundances of 10B and 11B and a crystal highly enriched with 10B. The as-grown crystals contain isolated oxygen vacancies, lithium vacancies, and copper impurities, all in nonparamagnetic charge states. During an irradiation at 77 K with 60 kV x-rays, doubly ionized oxygen vacancies trap electrons while singly ionized lithium vacancies and monovalent copper impurities trap holes. The vacancies return to their preirradiation charge states when the temperature of the sample is increased to approximately 90 K. Hyperfine interactions with 10B and 11B nuclei, observed between 13 and 40 K in the radiation-induced EPR and ENDOR spectra, provide models for the two vacancy-related defects. The electron trapped by an oxygen vacancy is localized primarily on only one of the two neighboring boron ions while the hole stabilized by a lithium vacancy is localized on a neighboring oxygen ion with nearly equal interactions with the two boron ions adjacent to the oxygen ion.

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Identification of electron and hole traps in lithium tetraborate (Li ₂B₄O₇) crystals: Oxygen vacancies and lithium vacancies

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