Regensburg 2007 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 10: Dielectric and Ferroelectric Thin Films and Nanostructures III
DF 10.1: Vortrag
Donnerstag, 29. März 2007, 14:30–14:50, H48
Structure and charge modulations in the mixed oxides In2O3(ZnO)m: Electron holography and quantum chemical computations — •Falk Röder1, Martin Linck1, Hannes Lichte1, Thomas Bredow2, Oliver Köster-Scherger3, and Werner Mader3 — 1Institute of Structure Physics, Triebenberg Lab, Technische Universitaet Dresden — 2Institute for Physical and Theoretical Chemistry, University of Bonn — 3Institute for Inorganic Chemistry, University of Bonn
Compounds of the type In2O3(ZnO)m, m = 2,3,4,..., are ideal model systems of wide-spaced electric field modulations, to study distribution and relaxation of charge in solids for the first time. They consist of ZnO domains separated by fully occupied layers of In3+ ions and layers of unoccupied metal sites. These layers are strictly alternating and periodically arranged at a spacing controllable by the quantity m. Formally, the layers carry a charge of one electron per site, which would produce huge electric fields of ca. 200 GV/m without accounting for structural and electronic relaxations. In a TEM, the respective intrinsic electric fields modulate the phase of the electron wave hence are measurable by means of electron holography; in fact, they are clearly revealed from the reconstructed phase images. Quantum chemical computations were performed for compounds with m = 3;5 using the crystalline orbital program package CRYSTAL06. It is found that half of the In3+ ions occupy sites close to the unoccupied layers. The calculated electric fields are used to interpret the results of the electron holographic measurements.