Berlin 2015 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

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

DF 9.3: Vortrag

Dienstag, 17. März 2015, 14:40–15:00, EB 107

Domain structure in anisotropically strained K_0.75Na_0.25NbO₃ thin films on TbScO₃ — •Dorothee Braun¹, Albert Kwasniewski¹, Philipp Müller¹, Martin Schmidbauer¹, Jan Sellmann¹, Michael Hanke², and Jutta Schwarzkopf¹ — ¹Leibniz-Institute for Crystal Growth, Berlin, Germany — ²Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany

Understanding and controlling of domain formation in ferroelectric thin films at the nanoscale is essential for fundamental research as well as for potential applications. The incorporation of anisotropic in-plane lattice strain has a decisive impact on the stability of ferroelectric phases and is achieved by the deposition on lattice mismatched substrates. In this study 30 nm thick K_0.75Na_0.25NbO₃ films were epitaxially grown on TbScO₃ substrates by metal-organic chemical vapor deposition. They experience in average a slight compressive lattice strain of 0.47% and are (100)_c oriented. Our PFM measurement revealed both a lateral and a vertical component of the polarization vector whereby the latter one is less pronounced. The lateral PFM shows regularly arranged 90^∘ domains in two directions with domain walls running along <110> and a periodicity of 50 nm has been observed. According to x-ray measurements, the films are grown fully strained on the substrate. The film unit cell is monoclinically distorted in the vertical direction, but no in-plane monoclinic distortion has been detected. These results indicate the occurrence of monoclinic M_C domains which were not observed in (K,Na)NbO₃ thin films before.