Metallic oxides as dielectrics in artificially layered ferroelectric superlattices

Artificially structured oxides provide many opportunities to develop systems with novel and tunable properties. SrRuO$_3$ has a metal-insulator transition as a function of thickness, which suggested to us the idea that we could use extremely thin layers (less than 3 unit cells) of SrRuO$_{3}$ as a novel dielectric component within an artificially layered superlattice system. We have created high quality PbTiO$_3$/SrRuO$_3$ superlattices by using an off-axis RF magnetron sputtering technique. The samples were characterized by x-ray diffraction, atomic force microscopy, transmission electron microscopy, and electrical measurements. When the PbTiO$_3$ layers are above a certain critical thickness, significant out-of-plane ferroelectricity develops in the system and the overall material has a semiconducting character. In this talk we will present a detailed experimental investigation of the behavior of ferroelectric polarization and domain size as the relative thicknesses of the superlattice layers are varied. Our work serves as a demonstration that a new set of materials, metallic oxides, can be considered for inclusion as novel dielectric layers in ferroelectric superlattices.