Size effect and fatigue mechanism in ferroelectric thin films

Ferroelectric thin films such as barium strontium titanate (BST) and lead zirconate titanate (PZT) are potential materials for high-density dynamic/ferroelectric random-access memory applications. However, the properties of BST and PZT thin films are observed to be significantly inferior to their bulk counterparts. In addition, ferroelectric PZT films, when configured with metal electrodes, generally experience loss of switchable polarization (fatigue) under repetitive electrical cycling. We have reported previously that an interfacial defect layer was observed in BST/Pt interfaces. In this article, we discussed the possible origin of the interfacial defect layer and the effect it has on the thickness-dependent properties. We further suggested that fatigue in ferroelectrics could be explained by a field screening mechanism in which only a small fraction of the applied voltage is seen by the film bulk due to the screening effect of the interfacial layers.