Polarization states of polydomain epitaxial Pb(Zr1-xTix)O3 thin films and their dielectric properties

TL;DR

This paper uses a nonlinear thermodynamic theory to analyze the polarization states and dielectric properties of polydomain Pb(Zr1-xTix)O3 thin films across various compositions, revealing complex phase diagrams and strain-dependent behaviors.

Contribution

It develops phase diagrams for PZT films with different compositions, highlighting the presence of monoclinic polydomain states and their impact on polarization and dielectric response.

Findings

Similar phase diagrams for x > 0.7 to PbTiO3

Rich polarization states including monoclinic domains at x = 0.4-0.6

Theoretical polarization matches experimental remanent polarization data

Abstract

Ferroelectric and dielectric properties of polydomain (twinned) single-crystal Pb(Zr1-xTix)O3 thin films are described with the aid of a nonlinear thermodynamic theory, which has been developed recently for epitaxial ferroelectric films with dense laminar domain structures. For Pb(Zr1-xTix)O3 (PZT) films with compositions x = 0.9, 0.8, 0.7, 0.6, 0.5, and 0.4, the "misfit strain-temperature" phase diagrams are calculated and compared with each other. It is found that the equilibrium diagrams of PZT films with x > 0.7 are similar to the diagram of PbTiO3 films. They consist of only four different stability ranges, which correspond to the paraelectric phase, single-domain tetragonal ferroelectric phase, and two pseudo-tetragonal domain patterns. In contrast, at x = 0.4, 0.5, and 0.6, the equilibrium diagram displays a rich variety of stable polarization states, involving at least one monoclinic polydomain state. Using the developed phase diagrams, the mean out-of-plane polarization of a poled PZT film is calculated as a function of the misfit strain and composition. Theoretical results are compared with the measured remanent polarizations of PZT films grown on SrTiO3. Dependence of the out-of-plane dielectric response of PZT films on the misfit strain in the heterostructure is also reported.