Berlin 2015 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 36: Poster Session I

DS 36.27: Poster

Donnerstag, 19. März 2015, 09:30–12:00, Poster A

Bias Voltage Effect and Interfacial Capacitance of Manganite-Titanite Heterostructures — •Vitaly Bruchmann-Bamberg, Markus Michelmann, and Vasily Moshnyaga — I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Pl. 1, 37077 Göttingen

Dielectric properties and polarization switching in epitaxial thin films of ferroelectric oxides are governed by both misfit strain and interfacial capacitance (so-called "dead layers"). While BaTiO₃-based titanites as a thin film show a remarkable enhancement of the Curie-temperature under homogenous compressive strain, strain gradients are discussed as driving force behind the bias voltage and the loss of remanence in ferroelectric hysteresis loops due to the flexoelectric effect.

We prepared epitaxially grown metal-dielectric-metal heterostructures on SrTiO₃ substrates with metallic La_0.7Sr_0.3MnO₃, ferroelectric Ba_0.5Sr_0.5TiO₃ and paralectric SrTiO₃ by means of metalorganic aerosol deposition. By varying the BSTO-layer thickness, different stages of lattice relaxation with an in-plane compressive strain can be observed. Ferroelectric hysteresis is characterized by dielectric spectroscopy and the Positive-Up Negative-Down technique. Furthermore, an interfacial capacitance at the manganite-titanite-interface leads to a significant reduction of dielectric tunability and ferroelectric remanence. The results are discussed within the framework of flexoelectric coupling between strain and polarisation and interfacial Schottky-barrier formation. As an outlook, first results on engineering dead layers via an LaMnO₃ and SrMnO₃ interlayers and heterostructures with lattice matched Ba_1−xCa_xTiO₃ films will be presented.