Regensburg 2010 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 29: Poster: Molecular Spintronics, Biomolecular and Functional Organic Layers, Organic Electronics and Photovoltaics, Plasmonics and Nanophotonics, Organic Thin Films, Nanoengineered Thin Films, Thin Film Characterisation,

DS 29.45: Poster

Mittwoch, 24. März 2010, 15:00–17:30, Poster A

Structural and electrical properties of SrTiO3 films grown on CeO2 buffered sapphire — •Eugen Hollmann, Rolf Kutzner, Jurgen Schubert, Gregor Mussler, and Roger Wördenweber — Institute for Bio- and Nanosystems (IBN2), Research Center Juelich, Germany

The physical properties of complex oxides like ferroelectric perovskite are strongly connected with their composition, structure and structural imperfections. Lattice constants and thermal properties of substrate materials and deposited films are usually different. In the case of thin epitaxial films this difference can be used for engineering of properties of ferroelectric materials via mechanical strain due to changing of film thickness and preparation conditions.

In the present work we report on results of measuring the strain of both in buffer CeO2 and STO films on r-cut sapphire. Ferroelectric films were deposited by PLD. Different types of strain lead to various structural modifications in films. The resulting type of distortion and defects are investigated by high-resolution x-ray analysis. Electrical properties of STO films of various thicknesses are measured using planar capacitors in a wide frequencies range.

It is shown that in the thinner films the stress is compensated by misfit dislocations generated during growth and a deformation of the STO lattice. With increasing film thickness cracks develop in two crystalline directions, i.e. along the [1210] and, additionally, the [1010] directions of r-cut sapphire. The strained films show a strong modification of temperature dependence of the dielectric permittivity.