Regensburg 2002 – wissenschaftliches Programm

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DF: Dielektrische Festkörper

DF 6: Poster

DF 6.1: Poster

Mittwoch, 13. März 2002, 14:30–18:00, Poster Chemie C

The growth mechanism of epitaxial BaTiO₃ films on vicinal SrTiO₃ (001) surfaces — •Alina Visinoiu, Marin Alexe, Ho Nyung Lee, Dmitri N. Zakharov, Alain Pignolet, and Dietrich Hesse — Max-Planck-Institut für Mikrostrukturphysik

Initial growth stages of BaTiO₃ films are studied by AFM, HRTEM, and XRD. Epitaxial BaTiO₃ thin films were grown on Nb-doped SrTiO₃ (001) substrates by PLD. Vicinal substrate surfaces with well-defined terraces were prepared by etching and annealing treatments. Due to the low BaTiO₃/SrTiO₃ mismatch (2.28%), the BaTiO₃ films grow coherently and with a layer-then-island (Stranski-Krastanov) growth mechanism as observed by analyzing the morphology of a sequence of films. Initially, a uniform grainy layer of about 5 nm in thickness covers the substrate surface. Increasing the film thickness, the film stress relaxes and individual grains begin to grow. Due to coalescence, these small grains then constitute the nucleation sites for large grains of about 100 nm in lateral size which become the origins of a columnar structure of thick BaTiO₃ films. Up to 6 nm in thickness, the BaTiO₃ films showed no defects and a sharp film/substrate interface. The crystallinity of the deposited films was investigated by x-ray diffraction θ-2θ scans, pole-figures and φ scans. The remanent polarization and coercive field of Pt/BaTiO₃/SrTiO₃:Nb heterostructures are 1.53 µC/cm² and 36.4 kV/cm, respectively. The room temperature relative dielectric constant and the dielectric loss are about 615 at 10 kHz and 0.04, respectively.