High-Performance Epitaxial PZT Ferroelectric Membranes Fabricated via Water-Soluble CaO Sacrificial Layers on Sapphire Substrates

Abstract

Freestanding epitaxial ferroelectric membranes are essential for the advancement of flexible electronics and high-performance integrated devices. While water-soluble Sr₃Al₂O₆ sacrificial layers are commonly used to produce such membranes, the requirement for SrTiO₃ substrates limits their scalability and increases production costs. In this study, we report the synthesis of high-quality, epitaxial PbZr_0.52Ti_0.48O₃ (PZT) freestanding sheets using a cost-effective and scalable r-plane Al₂O₃ (sapphire) substrate with a water-soluble CaO sacrificial layer. By incorporating a thin BaTiO₃ buffer layer to prevent interfacial reactions, we successfully obtained crack-free, c-axis-oriented PZT membranes via a simple water-immersion process. The resulting PZT sheets exhibited a remarkably high remnant polarization of 58 μC/cm², which is larger than that reported in PZT membranes grown on Sr₃Al₂O₆/SrTiO₃ and closely approaches the values of bulk PZT. Furthermore, the sheets maintained a low dielectric loss. Our findings demonstrate that the CaO/sapphire platform provides a scalable and efficient pathway for fabricating high-performance epitaxial ferroelectric membranes, facilitating their integration into next-generation flexible and large-area electronic systems.