Harnessing competition in artificially layered ferroelectric superlattices to engineer enhanced piezoelectrics

First principles calculations by Cooper and Rabe (V. R. Cooper and K.M. Rabe, Phys. Rev. B 79, 180101 (R) (2009)), predicted that in PbTiO$_{3}$/BaTiO$_{3}$ superlattices an enhancement of the d$_{33}$ piezoelectric coefficient could be achieved at a particular ratio of the thickness of the constituent layers. We have fabricated high quality artificially layered PbTiO$_{3}$/BaTiO$_{3}$ superlattices on SrTiO$_{3}$ substrates (with SrRuO$_{3}$ bottom electrodes) using an off-axis RF magnetron sputtering technique, allowing us to perform x-ray diffraction, electrical measurements and atomic force microscopy on this system. The experimental results confirm the prediction from first principles calculations, and we apply a Landau theory model as a useful bridge between the first principles predictions and experimental results at elevated temperature. In this work we have demonstrated that by finely balancing competing material properties in artificial heterostructures, desirable properties that exceed those of the parent compounds can be achieved.