SKM 2021 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 5: Poster Session KFM

KFM 5.8: Poster

Dienstag, 28. September 2021, 16:00–17:00, P

Light-induced transient absorption of lithium niobate as a function of temperature and composition — •Mira Hesselink, Simon Messerschmidt, Laura Vittadello, and Mirco Imlau — Department of Physics, Osnabrueck University, Germany

Small polaron hopping in lithium niobate, LiNbO₃ (LN), takes a crucial role in optical process. Its behavior is investigated with a systematic study as a function of temperature, composition and doping. [Messerschmidt, S. et al. Crystals 2020, 10, 109.; Vittadello, L. et al. Crystals 2018, 8, 294.] The number and type of hopping processes are measured by means of light-induced transient absorption spectroscopy. All measurements are performed in a cryostat using a setup with ns-pump and cw-probe. Different sample compositions and dopings (Fe- or Mg-doped LN) go along with different polaron traps inside the crystal. At room temperature, the absorption signals decay in the range of milliseconds, while at lower T the processes are slowed down extensively. The decay rate of the light-induced absorption in Mg:LN appears Arrhenius temperature dependent in range 200K - 120K but this dependence weakens and becomes non-Arrhenius as T is lowered. For the Fe:LN, it is observed that different temperatures lead to different hopping processes by measuring the activation energy. Moreover, the experimental results are in good coincidence with numerical and analytical models based on the Holstein theory. At elevated T ionic diffusion is expected to play a big role and the influence on polaronic charge transport is to be investigated in a next step. Financial support by the DFG (IM3/12-1, FOR 5044) is gratefully acknowledged.