Regensburg 2007 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 11: Poster Session

DF 11.18: Poster

Donnerstag, 29. März 2007, 14:30–18:00, Poster C

Comparison of light-induced absorption in nominally pure LiNbO₃ and LiNbO₃ doped with different concentrations of Mg or Zn — •Daniela Conradi, Christoph Merschjann, Bettina Schoke, and Mirco Imlau — Department of Physics, University of Osnabrück, Barbarastr. 7, D-49069 Osnabrück

Nominally pure LiNbO₃ has a tendency of non-stoichiometry ([Li]/[Nb]<1), leading to the incorporation of Nb_Li-antisite-defects and Li-vacancies. Bound Nb_Li⁴⁺ small polarons, Nb_Li⁴⁺:Nb_Nb⁴⁺ bipolarons and bound O⁻ hole polarons, all yielding broad absorption bands in the VIS and NIR spectrum, are related to these intrinsic defects. Intense light illumination leads to a metastable population of the polaronic states, which is observed as a transient light induced absorption. Mg- and Zn-doping suppresses the intrinsic defects. The behavior of the small polarons thus depends on the doping concentration. We investigate the photochromic effect in nominally pure LiNbO₃ and Mg- and Zn- doped LiNbO₃ by means of excited-state-absorption spectroscopy using ns laser pulses of λ = 532 nm and probe light in the VIS and NIR region. The temporal and spectral behavior of the photo-induced small polarons is studied and the influence of doping on the concentration and the lifetime of metastable polarons is discussed. Supported by the Deutsche Forschungsgemeinschaft (IM 37/2-2, TFB 13-04 and GRK 695).