Synthesis and Phase Transition of Large‐Area Layered Ferroelectric Semiconductor α‐In₂Se₃ via 2D Solid‐Phase Crystallization

Ferroelectric semiconductor α‐In 2 Se 3 has gained significant attention due to its favorable physical characteristics, including an appropriate bandgap (≈1.4 eV) for semiconductor devices, intercorrelated out‐of‐plane and in‐plane polarization, and high Curie temperature (>200 °C). Combining its semiconducting and ferroelectric properties, α‐In 2 Se 3 holds promise for developing many innovative applications. However, the large‐scale synthesis of uniform layered α‐In 2 Se 3 for practical use and a comprehensive understanding of its phase transition during synthesis are lacking. In this study, layered α‐In 2 Se 3 on amorphous SiO 2 substrates at a cm 2 ‐scale is successfully synthesized and explored its phase transition during synthesis, by using a 2D solid‐phase crystallization (2DSPC) method with a SiO 2 encapsulation. The formation of highly crystalline 2D layered α‐In 2 Se 3 is observed through the real‐time β‐phase to α‐phase transition at room temperature. The electrical (field‐effect mobility µ FE ≈ 1 cm 2 V −1 s −1 ), optical, and ferroelectric properties of the synthesized α‐In 2 Se 3 thin films are further investigated. This study contributes to the understanding and control of stoichiometry and phases of In 2 Se 3 and provides an efficient approach for synthesizing large‐area 2D layered α‐In 2 Se 3 .