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DF: Fachverband Dielektrische Festkörper

DF 8: Dielectric and Ferroelectric Thin Films and Nanostructures II

DF 8.1: Invited Talk

Wednesday, March 28, 2007, 14:30–15:10, H11

Piezoelectricity and pyroelectricity in amorphous perovskite thin films — •Alexander K. Tagantsev¹, Vera Lyahovitsky², David Ehre², Ellen Wachtel², Sidney R. Cohen², Konstantin Gartsman², and Igor Lubomirsky² — ¹Swiss Federal Institute of Technology (EPFL), Lausanne 1015, Switzerland — ²Weizmann Institute of Science, Rehovot 76100, Israel

One customarily considers the crystallinity as a prerequisite for pyro- and piezoelectricity in a material. Though the theory does not impose such limitation, the long-standing experience in the field tells us that ionic structures exhibiting pyro- and piezoelectricity should be at least polycrystalline. In this paper, we demonstrate that the ”common“ behavior of perovskite dielectrics can be revolutionary influenced when thin films of these materials are treated with a specially tailored temperature gradient. Such treatment enables the transformation of non-polar amorphous films of BaTiO₃, SrTiO₃, and BaZnO₃ into a polar state that exhibits appreciable values of pyro- and piezoelectric coefficients. One should stress that, in the case of SrTiO₃ and BaZnO₃, the polar amorphous films are prepared from originally non-polar materials. This unusual phenomenon raises a body of intriguing questions concerning the physics behind it. In this paper we address two of these issues in detail: (i) the mechanism of temperature-gradient driven amorphous-to-amorphous-state transformation and (ii) the mechanism of polar-state formation in the amorphous materials.