Berlin 2018 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 6: Ferroelectric Domain Walls II (joint session KFM/TT)

KFM 6.5: Talk

Monday, March 12, 2018, 16:30–16:45, EMH 225

Formation of ferroelectric monoclinic domains in K_0.7Na_0.3NbO₃ thin films under different strain conditions — •Leonard von Helden¹, Martin Schmidbauer¹, Michael Hanke², and Jutta Schwarzkopf¹ — ¹Leibniz Institute for Crystal Growth (IKZ), Berlin — ²Paul-Drude-Institute for Solid State Electronics (PDI), Berlin

K_xNa_1−xNbO₃ is a promising material for lead-free ferro- and piezoelectric applications due to its high piezoelectric and coupling coefficients. Moreover, monoclinic phases - which are favorable as they enable a continuous rotation of the polarization vector - can be induced by incorporating anisotropic epitaxial lattice strain in K_xNa_1−xNbO₃ thin films. Upon varying the strain conditions the symmetry and orientation of these monoclinic domains can be deliberately tailored as predicted by strain-phase calculations.^[1] In order to confirm the theoretical predictions we present a systematic investigation on the ferroelectric domain formation in K_0.7Na_0.3NbO₃ thin films grown by MOCVD. Slightly different strain conditions were realized by the application of various (110) oriented rare earth scandate substrates. The resulting ferroelectric domain structure was investigated upon a combination of piezoresponse force microscopy and X-ray nano-diffraction. Our results reveal monoclinic M_C domains with (001)_pc pseudocubic unit cell orientation that differ among the substrates regarding their domain wall inclination. Moreover, the additional occurrence of (100)_pc unit cell orientation in films with a thickness above 60 nm will be discussed. [1] J. Schwarzkopf et al., Front. Mater. 4, 26 (2017).