Impact of misfit relaxation and a-domain formation on the electrical properties of tetragonal PbZr_(0.4)Ti_(0.6)O_3/PbZr_(0.2)Ti_(0.8)O_3 thin film heterostructures: Experiment and theoretical approach

摘要

Heterostructures consisting of PbZr_(0.2)Ti_(0.8)O_3 and PbZr_(0.4)Ti_(0.6)O_3 epitaxial films on a SrTiO_3 (100) substrate with a SrRuO_3 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° 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.