Regensburg 2000 – scientific programme

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DF: Dielektrische Festkörper

DF 7: Poster

DF 7.3: Poster

Thursday, March 30, 2000, 09:30–13:00, C

Light-induced absorption in pure and Fe-doped BCT-crystals — •M. Wierschem, T. Lindemann, S. Kapphan, and R. Pankrath — FB Physik, University of Osnabrück, Barbarastraße 7, D-49069 Osnabrück, Germany

Ba_1−xCa_xTi:O₃ (BCT, with congruent composition for x=0.23) has similar promising photorefractive properties like BaTiO₃ but without its destructive phase transition just below room temperature. Fe-doping enhances the photorefractive properties and leads to broad additional absorption bands in the visible range. The UV-absorption edge is shifted with increasing Fe-doping to longer wavelengths. Illumination of the samples (AR⁺ 488nm) at T<70K yields a light-induced NIR-absorption band, very similar to NIR-absorption bands observed in reduced BCT due to Ti³⁺-polarons [1]. The light-induced NIR-absorption is investigated as a function of illumination intensity, polarization and temperature. The steady state and the kinetics of the light-induced NIR-absorption, after a fast switch-off of the illumination, can be described by a simple model of ight-induced charge transfer, similar to the case of Nb⁴⁺ polarons in SBN [2].

[1] A. Mazur, C. Veber, O. F. Schirmer, C. Kuper, H. Hesse, J. Appl. Phys. 85(9), 6751-6757, (1999)

[2] M. Gao, R. Pankrath, S. Kapphan, V. Vikhnin, Appl. Phys. B 68, 849 (1999)

This work has been supported by DFG (SFB225-C7).