Ultra-thin and isolated dots in polycrystalline lead zirconate titanate films

Size effects with critical thickness or minimum volume for ferroelectricity are of importance in the application of polycrystalline PZT thin films as future memory devices and as storage media. Isolated dots of perovskite phases in the matrix of pyrochlore were synthesized by isothermal annealing through transformation from amorphous to perovskite. Control of the transformation kinetics allows us to produce the isolated ferroelectric dots with a diameter of 50 nm. Domain structure of the isolated dots is also studied by piezoresponse force microscopy. As prepared, all isolated dots contain perpendicularly polarized monodomains. Domain structures and switching behaviors of the isolated dots are similar to those of the single crystalline PZT films. Polycrystalline PZT films with a thickness of 50 nm were also investigated. They show excellent piezoresponse properties and switching behaviors. Ultra-thin polycrystalline PZT films can play a major role in the application of future ferroelectric memories and field-effect transistors as well as for storage media using the local probe technique.