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Mccloy, John S.
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Publications (8/8 displayed)
- 2023Persistent optical phenomena in oxide semiconductorscitations
- 2023Micro- and Nanoscale Surface Analysis of Late Iron Age Glass from Broborg, a Vitrified Swedish Hillfortcitations
- 2022Growth and defect characterization of doped and undoped β-Ga2O3 crystalscitations
- 2022Alternative alloy to increase bandgap in gallium Oxide, β-(Sc Ga1-)2O3, and rare earth Stark luminescencecitations
- 2017Apatite and sodalite based glass-bonded waste forms for immobilization of 129I and mixed halide radioactive wastes
- 2014Preliminary Phase Field Computational Model Development
- 2009Electromagnetic material changes for remote detection and monitoring: a feasibility study: Progress report
- 2008FY 2008 Infrared Photonics Final Report
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document
Persistent optical phenomena in oxide semiconductors
Abstract
The interaction of transparent oxide semiconductors with light is critically important for a range of applications. Persistent effects could be exploited for holographic memory or optically defined circuits. Conversely, they may also be detrimental to device operation. Large, room-temperature persistent photoconductivity (PPC) was discovered in strontium titanate (SrTiO<sub>3</sub>, STO) after annealing in a hydrogen-containing atmosphere. Barium titanate (BaTiO<sub>3</sub>, BTO), a ferroelectric material, was recently found to also exhibit PPC. Room-temperature photodarkening was observed in Cu-doped gallium oxide (β-Ga<sub>2</sub>O<sub>3</sub>) after exposure to sub-bandgap light. Hydrogen is believed to play a central role in these persistent phenomena. In the proposed model, a photon excites substitutional hydrogen (a proton inside an oxygen vacancy), making the defect unstable. The proton leaves and binds to a host oxygen atom, forming an O-H bond that is observed with infrared spectroscopy. An oxygen vacancy is left behind. Because oxygen vacancies in STO and BTO are shallow donors, this process results in PPC. In β-Ga<sub>2</sub>O<sub>3</sub>:Cu, however, the oxygen vacancy neighbors a Cu acceptor. In that case, photoexcitation results in the rare Cu<sup>3+</sup> state, which absorbs visible light. The effect can be “erased” by annealing at 300-400°C.