Dresden 2014 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 18: Dielectric and ferroelectric thin films

DF 18.6: Vortrag

Mittwoch, 2. April 2014, 17:40–18:00, GER 37

Epitaxial PLD growth of strained ferroelectric KxNax-1NbO3 thin films and superlattices — •Jan Sellmann, Jutta Schwarzkopf, Dorothee Braun, Andreas Duk, Albert Kwasniewski, and Martin Schmidbauer — Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin

(K,Na)NbO3 single crystals exhibit excellent ferro-/piezoelectric properties, however, they are less investigated in thin film form. We have deposited KxNa1-xNbO3 single layers and (NaNbO3)n/(KNbO3)m superlattices epitaxially by Pulsed Laser Deposition (PLD) on various lattice mismatched substrates providing compressive and tensile lattice strain. KxNa1-xNbO3 films have been realized by the use of KxNa1-xNbO3 ceramics (x = 0 - 0.75) as PLD targets. Increased K incorporation up to x = 0.5 into the films leads to a significant improvement of both the piezoresponse and to an increased lattice mismatch between film and substrate. In order to obtain higher critical thicknesses for fully strained film growth superlattice structures were grown by the alternating deposition of NaNbO3 and KNbO3 films with individual film thicknesses between 1 to 20 monolayers. While alternating layers with nominal thicknesses of up to three monolayers result in single layers consisting of a KxNa1-xNbO3 solid solution, superlattice structures (NaNbO3)n/(KNbO3)m were successfully deposited with individual layer thicknesses of seven or more monolayers. In particular, high piezoresponse was obtained on films with 5x(NaNbO3)17/(KNbO3)9 superlattice structure. We present a detailed study of different m/n ratios on piezoresponse and local ferroelectric hysteresis curves.