Enhanced Ferroelectric Functionality in Flexible Lead Zirconate Titanate Films with In Situ Substrate-Clamping Compensation

Much attention has recently been given to flexible and wearable integrated electronic devices, with a strong emphasis on real-time sensing, computing, and communication technologies. Thin ferroelectric films exhibit switchable polarization and strong electromechanical coupling, and hence are in widespread use in such technologies, albeit not when flexed. Effects of extrinsic strain on thin ferroelectric films are still unclear, mainly due to the lack of suitable experimental systems that allow cross structural-functional characterization with in situ straining. Moreover, although the effects of intrinsic strain on ferroelectric films, e.g., due to film-substrate lattice mismatch, have been extensively investigated, it is unclear how these effects are influenced by external strain. A method to strain thin films homogenously in situ is developed, allowing structural characterization as well as functional switching and piezorsponse measurements at the nanoscale, while retaining the sample under constant straining conditions. Using this method, thin films of PbZr0.2Ti0.8O3, which were grown on a flexible mica substrate, are strained to reduce substrate clamping effects and increase the tetragonality. Consequently, the domain stability is increased, the coercive field value is decreased, and imprint effects are reduced. This method also allows direct characterization of the relationship between the lattice parameters and nanoscale properties of other flexible materials.