Berlin 2018 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 27: Postersession KFM

KFM 27.12: Poster

Donnerstag, 15. März 2018, 15:00–17:00, Poster E

Surface acoustic wave propagation in monoclinic ferroelectric phases in strained K_0.7Na_0.3NbO₃ thin films — •Jutta Schwarzkopf¹, Leonard von Helden¹, Sijia Liang², Roger Wördenweber², and Martin Schmidbauer¹ — ¹Leibniz Institute for Crystal Growth, Max-Born-Str. 2, Berlin, Germany — ²Peter Grünberg Institute, Forschungszentrum Jülich, Jülich, Germany

Formation of ferroelectric phases with monoclinic symmetry is expected to result in enhanced piezoelectric properties. Together with high coupling coefficients, this feature can be exploited for thin film surface acoustic wave (SAW) devices. K_xNa_1−xNbO₃ represents a suitable material system that does not only provide high coupling coefficients. In addition, monoclinic phases can be stabilized in thin films by applying anisotropic epitaxial strain. Though as known from previous studies [1], the formation of the monoclinic phase crucially depends on the incorporated lattice strain. In this work, 30 nm K_0.7Na_0.3NbO₃ films were grown epitaxially on (110) TbScO₃ and (110) GdScO₃ substrates by metal-organic chemical vapor deposition. The films exhibit a compressive strain state with pseudocubic (001)_pc surface orientation and periodically arranged ferroelectric stripe domains. Piezoresponse force microscopy and x-ray diffraction reveal a domain periodicity of 40 − 50 nm and domains walls that proceed along the [112] or [112] directions of the orthorhombic substrates. These films were used for SAW experiments. Differences in SAW propagation will be discussed with regard to the symmetry of different monoclinic phases.

[1] J. Schwarzkopf et al., Front. Mater. 4, 26 (2017)