Unidirectional electric field enables reversible ferroelectric domain engineering

The deterministic control of ferroelectric polarization via an external field is critical for advancing the technologies of modern information storage. Conventionally, reversible and cyclic polarization switching in ferroelectric materials requires bipolar electric fields. The present work demonstrates the efficient reversible and cyclic ferroelectric domain switching under a unipolar electric field in van der Waals ferroelectric CuInP₂S₆, enabled by Cu-ion migration across van der Waals gaps. It further unveils the remarkable “shape memory” effect of manipulated domains, and the programmable domain patterning under a unipolar electric field. These findings not only deepen the understanding of ferro-ionic coupling mechanism, but also provide insights into the origin of multiple polarization states, negative capacitance, and the quantized charge transport, paving the way for emerging storage technologies and low-power neuromorphic applications.