Impact of misfit strain on the properties of tetragonal Pb(Zr,Ti)O3 thin film heterostructures

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Heterostructures consisting of PbZr0.2Ti0.8O3 and PbZr0.4Ti0.6O3 films grown on a SrTiO3 (100) substrate with a SrRuO3 bottom electrode were prepared by pulsed laser deposition. Using the additional interface provided by the ferroelectric bilayer structure and changing the sequence of the layers, the dislocation content and domain patterns were varied. The resulting microstructure was investigated by transmission electron microscopy. Macroscopic ferroelectric measurements have shown a large impact of the formation of dislocations and 90° domains on the ferroelectric polarization and dielectric constant. A thermodynamic analysis using the LANDAU-GINZBURGDEVONSHIRE approach that takes into account the ratio of the thicknesses of the two ferroelectric layers and electrostatic coupling is used to describe the experimental data.