Regensburg 2007 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 7: Dielectric and Ferroelectric Thin Films and Nanostructures I

DF 7.3: Vortrag

Dienstag, 27. März 2007, 15:30–15:50, H11

The impact of interfaces and structural defects on the properties of tetragonal Pb(Zr,Ti)O₃ thin film heterostructures — •Ludwig Geske^1,2, Ionela Vrejoiu¹, Lucian Pintilie¹, Marin Alexe¹, and Dietrich Hesse¹ — ¹Max-Planck-Institut für Mikrostrukturphysik Halle — ²Institut für Physik, Martin-Luther-Universität Halle-Wittenberg

During the deposition of films on substrates with different lattice parameters internal stresses arise. Above a critical thickness h_c dislocations will be introduced. While cooling down from the high deposition temperature, new stresses arise due to the different thermal expansion coefficients of film and substrate, and due to structural phase transitions in PZT. As soon as the temperature is too low to create further dislocations, twin domains will form if the film thickness is above a critical thickness h_c,do. Heterostructures consisting of bilayers or multilayers of tetragonal Pb(Zr_0.2Ti_0.8)O₃ and Pb(Zr_0.4Ti_0.6)O₃ thin films were layer-by-layer grown onto vicinal SrTiO₃ (001) single crystals by pulsed laser deposition. The thickness of the individual layers, that of the entire PZT structure, and the sequence of layers were varied, to induce or suppress the formation of dislocations and/or ferroelectric twin domains. The ferroelectric and dielectric properties of the samples were studied by the Aixacct TF Analyzer 2000 and by an impedance analyzer. Structural investigations comprising defect analysis were performed by TEM and by AFM. It turns out that the properties of the heterostructures, in particular the dielectric constant and the remanent polarization, are clearly influenced by the defect contents.