Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 52: Heterostructures

HL 52.3: Talk

Thursday, March 25, 2010, 10:30–10:45, H17

Crystal structure and dielectric function of BaTiO₃/ZnO heterostructures with applied electric bias — •Tammo Böntgen, Stefan Schöche, Rüdiger Schmidt-Grund, Chris Sturm, Mathias Brandt, Holger Hochmuth, Michael Lorenz, and Marius Grundmann — Universtät Leipzig, Institut für Experimentelle Physik II, Linnestr. 5

The orientation of the ferroelectric polarization of BaTiO₃ (BTO) in heterostructures composed of a BTO layer and a conductive ZnO layer, exhibiting a non-switchable spontaneous polarization, can be controlled by an applied electrical bias giving rise to a persistent change in the complex dielectric function (DF). We present first measurements of the DF of epitaxial perovskite BTO/ZnO heterostructures and its change under the effect of an applied electric field. In addition we show detailed investigations of the structural quality and the surface morphology measured by X-Ray diffraction (XRD) and atomic force microscopy. The DF is determined by means of spectroscopic ellipsometry (SE). The SE data are analyzed by a layer-stack analysis. The DF of the different layers were modeled with parameterized model DF and the energies of band-to-band transitions as well as the refractive index spectra were derived.
The interest in the optical properties of BTO and BTO heterostructures is based on its switchable ferroelectric properties, which make it a suitable material for application in e.g. thin film capacitators, nonvolatile memory or electronic switchers for optical signals[1].
[1] V.M. Voora et al., App. Phys. Lett. 95, 082902 (2009)