Berlin 2008 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 11: Dielectric and ferroelectric thin films and nanostructures I

DF 11.7: Vortrag

Mittwoch, 27. Februar 2008, 16:00–16:20, EB 107

Investigations on ferroelectric properties of P(VDF/TrFE) and BaTiO₃ by local field and Monte Carlo computations — •Markus Kühn and Herbert Kliem — Saarland University, Institute of Electrical Engineering Physics, P.O. Box 151150, 66041 Saarbrücken, Germany.

For interacting model systems of the P(VDF/TrFE) copolymer and the BaTiO₃ crystal dynamic Monte Carlo simulations are performed. The systems consist of field-induced point dipoles and permanent dipoles / ions. Both ferroelectric systems are placed between two coplanar conducting electrodes. All electrostatic interactions are considered and the electrodes are described by the method of images. The permanent dipoles / ions fluctuate thermally activated in double well potentials according to the Boltzmann statistics. The long-range electrostatic interactions strongly influence the local fields at the dipoles / ions. The iterative algorithm consists of two steps. For each current configuration the local fields at the dipoles / ions are deterministically calculated. Then the transition times of the dipoles / ions which depend on the local electric fields are computed in a following weighted probabilistic Monte Carlo step. As the main result we find ferroelectric hysteresis loops and polarisation switching curves. Further results for P(VDF/TrFE) have shown that dielectric layers adjacent to the electrodes have an impact on the hystereses. Simulations of the (2 0 0)-plane for BaTiO₃ show a pronounced domain growth starting at the electrode. Snapshots of the system at different times further revealed a pronounced pinning effect at a discontinuity modelled by a vacancy.