Nano-scale Ferroelectric Domain Structure And Its Movement By Scanning Force Microscopy Study

Piezoresponse scanning force microscopy was applied to study the nanoscale ferroelectric domain structure and dynamics in thin films and nano-islands. First, the experimental setup was checked by the well-documented single crystal and optimized to achieve the spatial resolution of ferroelectric domains as high as 5 nm. Then the ferroelectric domain structures and dynamics in PbTiO3 thin films were investigated by this powerful tool. It was revealed that the crystallographic orientation, dimensional sizes and boundaries of ferroelectric grains significantly affect the domain structures of thin films. In polycrystalline thin films, the complex domain structures, such as orthogonal contacted a-a domains were formed due to the intricate electric and mechanical boundary conditions. These domain structures usually contained the charged domain walls and tended to be moved readily by the electric field. The in-plane rotation of a-a domains in the multilayered films was possible because of the mediation of 45°-tilted spike-like nano-domains. With respect to the PbTiO3 nano-island, a chemical solution deposition method was modified to deposit them onto the platinized substrate. The size-dependence of domain structures in the nano-islands was well studied by three-dimensional PFM. The domain structure was found transform from a symmetric a-a domains to an asymmetric twin domains as deceasing the grain size. The metastable domain structures (curved domain walls and asymmetric domains) exhibited in the nano-island smaller than 60 nm. And the critical size of transition between multidomain and monodomain was determined at least smaller than 40 nm in the nano-island.