Berlin 2012 – scientific programme

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DS: Fachverband Dünne Schichten

DS 2: Nanoengineered thin films

DS 2.1: Talk

Monday, March 26, 2012, 12:30–12:45, H 0111

Growth of strained, ferroelectric NaNbO3 thin films by pulsed laser deposition — •Jan Sellmann, Jutta Schwarzkopf, Andreas Duk, Albert Kwasniewski, Martin Schmidbauer, and Roberto Fornari — IKZ, Berlin, Deutschland

Due to its promising ferro-/piezoelectric properties and high Curie temperature NaNbO3 has attracted much attention. In contrast to bulk crystals, thin epitaxial films may incorporate and maintain a certain compressive or tensile lattice strain, depending on the used substrate/film combination. This deformation of the crystal lattice is known to strongly influence the ferroelectric properties of perovskites. In the case of NaNbO3 compressive strain is achieved in films deposited on NdGaO3 and SrTiO3 substrates while deposition on DyScO3 and TbScO3 leads to tensile in-plane strain. In order to characterize and practically apply the ferroelectric films, it is necessary to embed them in a capacitor structure for which we use pseudomorphically grown SrRuO3 as bottom electrodes. We report on the deposition of SrRuO3 and NaNbO3 single layers on SrTiO3, DyScO3, TbScO3 and NbGaO3 substrates by means of pulsed laser deposition. By adjusting the substrate temperature, the oxygen partial pressure and the laser frequency we have successfully deposited smooth, strained, single phase NaNbO3 thin films. Investigations of the films by atomic force microscopy and high resolution X-ray diffraction reveal the dependence of the surface morphology and the incorporated lattice strain on the deposition parameters and the lattice mismatch, respectively. All films exhibit piezoelectric properties, as proven by piezoresponse force microscopy.