Regensburg 2007 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 7: Dielectric and Ferroelectric Thin Films and Nanostructures I

DF 7.9: Vortrag

Dienstag, 27. März 2007, 17:30–17:50, H11

Size and strain effects in ultrathin epitaxial BaTiO₃ films grown by high pressure sputtering — •Adrian Petraru¹, Hermann Kohlstedt¹, Nikolay Pertsev¹, Ulrich Poppe¹, Axel Solbach², Uwe Klemradt², and Rainer Waser¹ — ¹Institut für Festkoerperforschung and CNI, Forschungszentrum Jülich GmbH, Jülich, Germany — ²II. Physikalisches Institut B, RWTH Aachen University, 52074 Aachen

High quality epitaxial BaTiO₃ films with thicknesses ranging from 2.8 nm to 175 nm were grown epitaxially on SrRuO₃-covered SrTiO₃ (001) substrates by high-pressure sputtering. The film structure was studied by conventional and synchrotron x-ray diffraction. The amount of the compressive strain in the BaTiO₃ films was measured by x-ray reciprocal space mapping (X-RSM)around the asymmetric (103) Bragg reflection. Ferroelectric capacitors were then fabricated by depositing SrRuO₃/Pt top electrodes, and the polarization-voltage hysteresis loops were recorded at the frequency 1 KHz. The observed thickness effect on the lattice parameters and polarization in BaTiO₃ films was analyzed in the light of strain and depolarizing-field effects using the nonlinear thermodynamic theory. The theoretical predictions are in reasonable agreement with the measured thickness dependencies, although the maximum experimental values of the spontaneous polarization and the out-of-plane lattice parameter exceed the theoretical estimates markedly (43 µC/cm² vs. 35 µC/cm² and 4.166 Åvs. 4.143 Å). Possible origins of the revealed discrepancy between theory and experiment are discussed.