Impact of misfit relaxation and a-domain formation on the electrical properties of tetragonal PbZr0.4Ti0.6O3/PbZr0.2Ti0.8O3 thin film heterostructures: Experiment and theoretical approach

Heterostructures consisting of PbZr0.2Ti0.8O3 and PbZr0.4Ti0.6O3 epitaxial films on a SrTiO3 (100) substrate with a SrRuO3 bottom electrode were prepared by pulsed laser deposition. By using the additional interface provided by the ferroelectric bilayer structure and changing the sequence of the layers, the content of dislocations and elastic domain types was varied in a controlled manner. The resulting microstructure was investigated by transmission electron microscopy. Macroscopic ferroelectric measurements have shown a large impact of the formation of dislocations and 90 degrees domain walls on the ferroelectric polarization and dielectric constant. A thermodynamic analysis using the Landau-Ginzburg-Devonshire approach that takes into account the ratio of the thicknesses of the two ferroelectric layers and electrostatic coupling is used to shed light on the experimental data.