Direct observation of domain dynamics in lead zirconate titanate thin films

We report observations of the ferroelectric domain structure in epitaxial l ead zirconate titanate (PZT) ferroelectric thin films using piezoresponse m icroscopy. Epitaxial PZT films with a nominal composition of PbZr0.2Ti0.8O3 were deposited onto single crystal SrTiO3 substrates by pulsed laser depos ition, with an epitaxial layer of La-Sr-Co-O as the bottom electrode. By ma nipulating the film thickness, a uniform 2-dimensional grid of 90 degrees d omains (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 substantia lly preferentially oriented and that nucleation of reverse 180 degrees doma ins occurs preferentially at 90 degrees domain interfaces. Polarization rev ersal occurs through the nucleation and subsequent growth of "semicircular/ elliptical" reverse domains, which subsequently consume the entire region a s a function of reversal time. The reversal is seen to fit a stretched expo nential.