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

Ferroelectric semiconductor α-In₂Se₃ 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-In₂Se₃ holds promise for developing many innovative applications. However, the large-scale synthesis of uniform layered α-In₂Se₃ for practical use and a comprehensive understanding of its phase transition during synthesis are lacking. In this study, layered α-In₂Se₃ on amorphous SiO₂ substrates at a cm²-scale is successfully synthesized and explored its phase transition during synthesis, by using a 2D solid-phase crystallization (2DSPC) method with a SiO₂ encapsulation. The formation of highly crystalline 2D layered α-In₂Se₃ is observed through the real-time β-phase to α-phase transition at room temperature. The electrical (field-effect mobility µ_FE ≈ 1 cm² V⁻¹s⁻¹), optical, and ferroelectric properties of the synthesized α-In₂Se₃ thin films are further investigated. This study contributes to the understanding and control of stoichiometry and phases of In₂Se₃ and provides an efficient approach for synthesizing large-area 2D layered α-In₂Se₃.