Reversible flexoelectric domain engineering at the nanoscale in van der Waals ferroelectrics.

The universal flexoelectric effect in solids provides a mechanical pathway for controlling electric polarization in ultrathin ferroelectrics, eliminating potential material breakdown from a giant electric field at the nanoscale. One challenge of this approach is arbitrary implementation, which is strongly hindered by one-way switching capability. Here, utilizing the innate flexibility of van der Waals materials, we demonstrate that ferroelectric polarization and domain structures can be mechanically, reversibly, and arbitrarily switched in two-dimensional CuInP₂S₆ via the nano-tip imprinting technique. The bidirectional flexoelectric control is attributed to the extended tip-induced deformation in two-dimensional systems with innate flexibility at the atomic scale. By employing an elastic substrate, artificial ferroelectric nanodomains with lateral sizes as small as ~80 nm are noninvasively generated in an area of 1 μm², equal to a density of 31.4 Gbit/in². Our results highlight the potential applications of van der Waals ferroelectrics in data storage and flexoelectronics. Flexoelectric effect may offer a voltage-free method to control the polarization in 2D ferroelectrics, but its widespread application remains challenging. Here, the authors report an approach to arbitrarily switch the ferroelectricity in 2D CuInP₂S₆. [ABSTRACT FROM AUTHOR]