New interface effects in ferroelectric thin films

Abstract
We discuss four things : First, that for ferroelectric thin films on metal electrodes, terms usually ignored in the calculation of band match-ups (negligible for Si devices) are quite large (ca. 0.5 eV) ; second, for ultra-thin films (ca. 7 nm) much of the voltage drop is inside the metal electrode ; third, that the oxygen vacancy gradient in perovskite oxides can be fitted to bulk and grain boundary diffusion, assumed quenched in at the deposition temperatures ; and fourth, that elemental bismuth at the surfaces of strontium bismuth tantalate (SBT) and other bismuth-compound ferroelectrics is not an artefact but arises from a phase separation and wetting transition of Bi₂O₃ on SBT grains, similar to that well known in ZnO-Bi₂O₃ varistors.