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DF: Fachverband Dielektrische Festkörper
DF 7: Dielectric and Ferroelectric Thin Films and Nanostructures I
DF 7.9: Talk
Tuesday, March 27, 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.