Piezoelectric and Optoelectronic Properties of Ultrathin Layered β′-In ₂ Se ₃ Grown by Chemical Vapor Deposition

Two-dimensional (2D) layered semiconductor In 2 Se 3 offers extraordinary opportunities for multifunctional electronic and optoelectronic applications owing to its intrinsic ferroelectric, piezoelectric, and photoelectric properties. However, synthesizing highly crystalline and ultrathin β′-In 2 Se 3 nanosheets while preserving their unique structural phase remains a significant challenge. Here, we epitaxially grow high-quality 2D β′-In 2 Se 3 nanosheets on mica substrates via atmospheric-pressure chemical vapor deposition (APCVD), achieving an ultrathin thickness down to 2.7 nm. The strong piezoelectric activity was observed in all as-grown β′-In 2 Se 3 films, highlighting the multifunctional electromechanical potential of β′-In 2 Se 3 . Electrical measurements revealed a transition from the intrinsic n-type nature to pronounced p-type gate-modulated behavior when the β′-In 2 Se 3 nanosheet was transferred to a SiO 2 /Si substrate from a mica substrate, suggesting that the substrate plays a dominant role in regulating the carrier transport characteristics of β′-In 2 Se 3 . Photodetectors based on the transferred β′-In 2 Se 3 nanosheets exhibit stable and efficient photoresponses. At a light power density of 0.09 mW/cm 2, the responsivity, the detectivity, and the external quantum efficiency (EQE) are up to 4.8 A/W, 7.5 × 10 11 Jones, and 900%, respectively, suggesting substantial photoconductive gain arising from trap-assisted photogating. Overall, this work not only achieves the high-quality growth of β′-In 2 Se 3 nanosheets but also highlights their considerable potential for multifunctional two-dimensional device applications, including photodetectors, interface-engineered transistors, and piezoelectric devices.