Abstract
An attempt is made to locate energy-levels associated with photochromic centers in the band gap of KTaO3 doped with nickel. The thermally-stimulated current and the kinetics of ESR lines under illumination are measured over the temperature range from 90 K to 300 K. The results suggest the following energy-level assignments: the energy-levels of oxygen-vacancy (Vo) with one electron, Ni3+-Vo with two electrons and Ni3+-Vo with one electron are 0.13–0.18 eV, 0.39 eV and 0.49 eV from the conduction band, respectively. On the other hand, Fe3+ acts as a deep acceptor. The kinetics of the photocurrent and ESR lines under coloring and bleaching are qualitatively explained by the three-center model proposed in this paper.
Published Version
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