Impact of high interface density on ferroelectric and structural properties of PbZr0.2Ti0.8O3/PbZr0.4Ti0.6O3 epitaxial multilayers

Multilayers consisting of two tetragonal compositions PbZr0.2Ti0.8O3 and PbZr0.4Ti0.6O3 were deposited onto a SrRuO3 electrode grown on a vicinal (100) SrTiO3 substrate. It has been shown by extensive structural investigations comprising transmission electron microscopy in conventional and high resolution mode, reciprocal space mapping and piezoresponse force microscopy that with decreasing layer thickness a transition from a-domains confined to individual layers to a-domains propagating through the whole film takes place. This is caused by the formation of a common strain state of all layers which is responsible for the observed enhancement of the electrical properties. These show a maximum in the product of remanent polarization and dielectric constant at a certain density of interfaces. If the interface density becomes too high the lattice distortion accompanying each interface deteriorates the properties of the multilayer structure.