Berlin 2015 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 36: Poster Session I
DS 36.86: Poster
Donnerstag, 19. März 2015, 09:30–12:00, Poster A
Ferroelectric properties of anisotropically strained epitaxial NaNbO3 films grown on NdGaO3 — •Biya Cai1, Jutta Schwarzkopf2, Eugen Hollmann1, Dorothee Braun2, Martin Schmidbauer2, and Roger Wördenweber1 — 11Peter Grünberg Institute (PGI) Jülich, D-52425 Jülich, Germany — 2Leibniz Institute for Crystal Growth, Max-Born-Str. 2, D-12489 Berlin, Germany
Due to the lattice mismatch between the film and substrate, an anisotropically in-plain strain can be imposed to an epitaxially grown film. NaNbO3 films are epitaxially deposited on (110) NdGaO3 via Metal Organic Chemical Vapor Deposition. X-ray analysis shows that above 15nm, relaxation of the compressive strain starts. The analysis of the complex permittivity of different thickness films (27 * 80nm) as a function of temperature, electric field direction, AC and DC electric field reveals that (i) the compressive strain shifts the temperature of maximum permittivity from about 628K of a bulk NaNbO3 to close to room temperature of thin films, (ii) the room temperature permittivity of these strained films is enhanced by up to a factor of almost 3 compared to that of bulk material, (iii) there is a strong anisotropy in all ferroelectric characteristics for electric field orientations and (iv) a strong dependence of the permittivity on the ac amplitude of the electric field as well as the dc component of the electric field. The experimental results are discussed in terms of theories on domain wall motions and effect of relaxor ferroelectrics. These strained films represent interesting candidates for the applications of surface acoustic wave sensors.