Nanoscale engineering of ferroelectric functionality

In epitaxial films of perovskite ferroelectrics, functionality can be controlled by size-strain-surface effects. Experimental evidence of such a possibility is demonstrated in epitaxial heterostructures of BaTiO 3 thin films and of (Ba,Sr)TiO 3 superlattices grown by pulsed laser deposition on La 0.5 Sr 0.5 CoO 3 /MgO (001). In epitaxial BaTiO 3 films, temperature of phase transition is shown to be a function of in-plane biaxial strain and film thickness. In epitaxial (Ba,Sr)TiO 3 superlattices, the dielectric permittivity, tunability, and temperature of phase transition are shown to be a function of strain and superlattice period. The technological and principal problems limiting nanoscale engineering of ferroelectric functionality are also discussed.