Regensburg 2007 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 11: Poster Session

DF 11.10: Poster

Thursday, March 29, 2007, 14:30–18:00, Poster C

Simulation and Electron Holographic Investigation of the Polarization Field in Ferroelectric (BaTiO3) / Antiferroelectric (WO3) Structures — •Dorin Geiger, Axel Rother, Christopher Matzeck, and Hannes Lichte — Triebenberg Laboratory, Institute of Structure Physics, Technische Universitaet Dresden, D-01062 Dresden, Germany

Electron holography is an adequate instrument to study electric field distributions on an atomic scale by quantitative determination of both amplitude and phase in the object exit wave. In particular the phase is directly proportional to the projected Coulomb potential of the specimen in the case of slowly varying or weak potentials. Ferroelectrics intrinsically comprise a permanent electric polarization field that can be directly extracted from the phase. The unit cell structure, the geometry of the electrically polarized area (domain) and depolarization fields produce the shape of the potential wedge. For both ferroelectric (BaTiO3) and antiferroelectric (WO3) materials the macroscopic fields are calculated for differently shaped domains on different length scales using homogeneously polarized unit cells, whereas the polarization density and the local Coulomb potential is calculated from ab-initio principles, i.e. Density Functional Theory. For comparison with the simulations, electron holograms are recorded. The observed phase wedge is used for determination of the permanent polarization of the structure. [1] Support from DFG in the Framework of FOR 520 is gratefully acknowledged.