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DF: Fachverband Dielektrische Festkörper

DF 12: Poster

DF 12.9: Poster

Mittwoch, 16. März 2011, 15:00–17:30, P1

Study of transient photocurrents in nominally pure LiNbO₃ depending on the reduction — •Andreas Buescher, Hauke Bruening, and Mirco Imlau — Department of Physics, University of Osnabrück, Barbarastr. 7, D-49069 Osnabrück, Germany

In thermally reduced, nominally pure LiNbO₃ the steady-state absorption is characterized by a broad absorption band at λ = 500  nm due to the presence of stable (Nb_Li⁴⁺:Nb_Nb⁴⁺)-bipolarons. Upon illumination with intense pulse laser light in the blue green spectral range (τ = 8 ns, λ = 532   nm) these bipolarons can be dissociated into metastable small free (Nb_Nb⁴⁺)-polarons and small bound (Nb_Li⁴⁺)-polarons. This mechanism is responsible for the strong photochromic properties of this material. Furthermore, but less often studied, these polarons contribute to the conductivity comparable to the features of extrinsic Fe-doping. We present first results of measurements to detect the transient photocurrents associated to bound polarons using a fast operational amplifier. Our study highlights the impact of the number density of optically generated small polarons, which can be controlled by the reduction pre-treatment. We discuss the results in the framework of optical and electrical properties of small polarons in LiNbO₃.

*Financial support by the DFG (project IM37/5-1) and DAAD (50445542) is gratefully acknowledged.