Direct observation of domain dynamics in lead zirconate titanate thin films

We report observations of the ferroelectric domain structure in epitaxial lead zirconate titanate (PZT) ferroelectric thin films using piezoresponse microscopy. Epitaxial PZT films with a nominal composition of PbZr0.2Ti0.8O3 were deposited onto single crystal SrTiO3 substrates by pulsed laser deposition, with an epitaxial layer of La-Sr-Co-O as the bottom electrode. By manipulating the film thickness, a uniform 2-dimensional grid of 90° domains (a-domains, i.e., c-axis in the plane of the film) has been induced. Our studies show that the polarization direction in the film is substantially preferentially oriented and that nucleation of reverse 180° domains occurs preferentially at 90° domain interfaces. Polarization reversal occurs through the nucleation and subsequent growth of "semicircular/elliptical" reverse domains, which subsequently consume the entire region as a function of reversal time. The reversal is seen to fit a stretched exponential.