Heterolayered lead zirconate titanate thin films of giant polarization

Heterolayered Pb(Zr1−xTix)O3 (PZT) films consisting of alternating PbZr0.8Ti0.2O3 and PbZr0.2Ti0.8O3 layers, which were successfully synthesized via a multistep sol-gel route, demonstrate giant polarizations. They show (001)/(100) preferred orientation, the degree of which is strongly affected by both the combination sequence and the number of alternating layers as well as the processing temperature. There occurs a strong interaction between the layers of the two different compositions, leading to the preferred orientations. Both the ferroelectric and dielectric properties are dependent on the number of alternating layers. The six-heterolayered PZT film shows a giant remnant polarization of as high as 71.9μC∕cm2 and a dielectric permittivity of 905, which can easily double those of the conventional polycrystalline PZT films. Studies of the polarization behaviors under subswitching fields suggest a domain wall pinning mechanism. The giant polarization observed at high electric field can be accounted for by the coupling and interactions between the rhombohedral and tetragonal layers.