Layered van der Waals Ferroelectric BiOI for High-Performance Multistate Memory.

Van der Waals layered ferroelectrics are considered promising candidates for next-generation nanoelectronic devices. Among these materials, two-dimensional (2D) oxyhalides have gained a significant amount of attention due to their excellent dielectric properties and electronic band structure. However, their ferroelectric polarization has been less extensively explored. In this study, we investigate the intrinsic ferroelectric properties of van der Waals bismuth oxyiodide (BiOI), which was synthesized by using mist chemical vapor deposition. Our findings reveal that BiOI exhibits a high Curie temperature of approximately 450 K, along with both in-plane and out-of-plane ferroelectric domain reversal. Additionally, BiOI-based ferroelectric memristors demonstrate a high switching ratio of 104, long-term retention of 104 s, remarkable cycle stability with up to 10 000 cycles, and the ability to store multistate data. This study provides a solid foundation for the further exploration of the ferroelectric properties of bismuth oxyhalides and paves the way for their potential applications in high-performance ferroelectric memory devices.