Regensburg 2013 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 16: Dielectric and ferroelectric thin films

DF 16.4: Talk

Wednesday, March 13, 2013, 11:40–12:00, H11

Investigation of growth conditions on structural and ferroelectric properties of strained NaNbO3 thin films grown by PLD — •Jan Sellmann, Jutta Schwarzkopf, Andreas Duk, Sonia Gnanapragasam, Albert Kwasniewski, Martin Schmidbauer, Toni Markurt, and Roberto Fornari — Leibniz-Institute for Crystal Growth, Max-Born-Str. 2, 12489 Berlin, Germany

Alkaline niobates have recently attracted much attention due to their promising piezoelectric properties and high Curie temperatures. It is known that the ferro-/piezoelectric properties of these perovskites are strongly correlated to distortions of the oxygen octahedra as well as to the stoichiometry of the films. In the present work, epitaxial NaNbO3 films have been deposited by Pulsed Laser Deposition under different growth conditions on various lattice-mismatched substrates, resulting in either compressive or tensile lattice strain. Systematical high resolution XRD and aberration corrected HR-TEM investigations of these films reveal that the incorporated lattice strain and the out of plane lattice parameter c depend both on the lattice mismatch to the substrate material and on the film stoichiometry governed by the applied deposition parameters like oxygen partial pressure and Na/Nb ratio in the PLD target. The chemical composition of the films is also considered to markedly affect the leakage current, therefore NaNbO3 targets with sodium excess were used in order to compensate Na deficiency in the films and the associated dielectric loss. First results have shown that epitaxially strained NaNbO3 films on SrTiO3 substrates exhibit ferroelectric behavior with a remnant polarization of 24*E-6 C/cm^2.