Role of 90° domains in lead zirconate titanate thin films

We report observations of the ferroelectric domain structure in epitaxial lead zirconate titanate (PbZr0.2Ti0.8O3) ferroelectric thin films using piezoresponse microscopy. By manipulating the film thickness, a uniform two-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 out of plane polarization direction in the film is preferentially oriented. 90° domains have been observed as regions of low piezoresponse, as compared to the fully c axis oriented regions. We have studied the influence of these 90° domains and the domain walls on the nucleation of polarization reversal. We observe that the nucleation occurs preferentially at 90° domain interfaces. Polarization reversal is seen to occur through the nucleation and subsequent growth of “semicircular/elliptical” reverse domains, which eventually consume the entire region as a function of reversal time.