Dresden 2011 – scientific programme
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DF: Fachverband Dielektrische Festkörper
DF 12: Poster
DF 12.9: Poster
Wednesday, March 16, 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 (NbLi4+:NbNb4+)-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 (NbNb4+)-polarons and small bound (NbLi4+)-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.