Interfaces in nanosize perovskite titanate ferroelectrics — microstructure and impact on selected properties

Misfit dislocations in epitaxial Pb(Zr 0 . 5 2 Ti 0 . 4 8 )O 3 (PZT) nanoislands on SrTiO 3 (001) substrates are shown to involve strain fields that distort the PZT lattice in a tube of material with a cross-section of about4 nm x 8 nm around each misfit dislocation. As a consequence, 10 nm thin nanoislands -around half of their volume being distorted - are not ferroelectric. This finding corresponds to an impact of the interfacial dislocations on the ferroelectric size effect. Moreover, an interface-related, size-dependent imprint effect -i. e., a vertical shift of the ferroelectric hysteresis loop -was observed in polycrystalline PZT and epitaxial BaTiO 3 nanoislands. In result, interfacial engineering is indispensable to obtain nanostructured ferroelectrics with stable polarization and switching properties.