Berlin 2015 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 9: Focused Session on Ferroic Domain Walls III (DF with MA)

DF 9.4: Talk

Tuesday, March 17, 2015, 15:00–15:20, EB 107

Ferroelectric Domains of partially relaxed NaNbO₃ films under tensile strain — •Jan Sellmann, Dorothee Braun, Albert Kwasniewski, Martin Schmidbauer, and Jutta Schwarzkopf — Leibniz-Institute for Crystal Growth, Max-Born-Str. 12489, Berlin

Lead-free alkaline niobates have recently attracted much attention due to their promising piezoelectric properties like high Curie temperatures. In thin film form they exhibit large densities of ferroelectric domains so that the domain walls are expected to contribute significantly to electrical and electromechanical responses of the material. In the present work, epitaxial NaNbO₃ films have been grown by Pulsed Laser Deposition under optimized growth conditions yielding 2D growth and nearly stoichiometric films. Tensile lattice strain was induced by the use of TbScO₃ substrates. Increasing the film thickness above the critical thickness the formation of misfit dislocations resulted in partial plastic lattice relaxation and thus a reduction of the effective in plane strain. Concurrently, the ferroelectric domain pattern changes at the critical thickness from lateral 1D a1/a2/a1/a2 stripes domains with exclusive in-plane polarization to a periodic stripe domain pattern with both vertical and lateral polarization components. The latter can be described as a1c/a2c domains with head-to-head configuration in some cases possibly resulting in charged domain walls. Similar results with regard to the domain structure have been found for NaNbO₃ thin films on DyScO₃ substrates. However, it is in contrast to NaNbO3 thin films grown on DyScO3 and TbScO₃ by MOCVD where in-plane domains are exclusively found well beyond the onset of plastic strain relaxation.