# Intercalation‐Induced Phase Transitions in Ferroelectric α‐In2Se3

## TL;DR

This paper shows how lithium ion intercalation in α-In2Se3 causes structural and electronic phase transitions, transforming it from a ferroelectric semiconductor to a metal.

## Contribution

The study demonstrates a novel platform for exploring ion-induced phase transitions in ferroelectric semiconductors using electrolyte gating.

## Key findings

- Lithium intercalation in α-In2Se3 induces transitions from ferroelectric semiconductor to dirty metal and then to metal.
- Ferroelectric hysteresis narrows and disappears with increased intercalation, indicating loss of switchable polarization.
- The process enables systematic investigation of ferroelectricity and electronic conduction interactions.

## Abstract

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.

Using the electrolyte gating technique, the van der Waals ferroelectric semiconductor α‐In2Se3 undergoes a series of transitions from a ferroelectric semiconductor to a dirty metal and finally to a metal, accompanied by a structural transformation. Concurrently, the ferroelectric hysteresis window progressively narrows and eventually disappears with enhanced lithium intercalation, indicating the evolution from switchable to non‐switchable polarization.