Intercalation-Induced Phase Transitions in Ferroelectric α-In2Se3.

Specific ions can be intercalated into functional materials using the electrolyte gating technique, which has been widely used to regulate channel conductance in transistors and develop low-power neuromorphic devices. However, in these devices, fundamental exploration of ion intercalation-induced structural phase transitions remains largely overlooked and rarely explored. Here, the lithium-based electrolyte gating technique is used to probe the collective interactions between ions, lattices, and electrons in a van der Waals ferroelectric semiconductor α-In2Se3. Using a polymer electrolyte as the lithium-ion reservoir and α-In2Se3 as the channel material, the intercalated lithium concentration via a gate electric field is modulated. This manipulation drives a phase transition in α-In2Se3 from a ferroelectric semiconductor to a dirty metal and finally to a metal, accompanied by a structural transformation. Concurrently, with enhanced intercalation, the ferroelectric hysteresis window progressively narrows and eventually disappears, indicating the evolution from switchable to non-switchable polarization. This study represents a promising platform for the artificial construction of correlated material systems, enabling a systematic investigation into the interaction of ferroelectricity and electronic conduction using ion intercalation.