Nanoscale domain switching behaviour in polycrystalline ferroelectric thin films.

We report on the nanoscale domain switching behaviour in polycrystalline tetragonal perovskite lead zirconate titanate (PZT) ferroelectric thin films investigated via piezoresponse force microscopy (PFM). Local domain structures were imaged as a function of varying biasing conditions and spatial location of the tip within 50-100 nm sized grains. Nanoscale piezoresponse images provided direct visual evidence of the complex interplay between electrical and mechanical fields in a polycrystalline system, which causes effects such as correlated switching between the grain of interest and neighbouring grains, ferroelastic domain switching, inhomogeneous piezostrain profiles and domain pinning on very minute length scales. Detailed investigations on mechanisms which induce such domain behaviour are presented.