Controlled Synthesis of High-Quality Ultrathin 2D In ₂ S ₃ Nanosheets and Their Applications in Optoelectronic Devices

The controllable synthesis of uniform, high-quality two-dimensional (2D) semiconductor crystals remains a significant challenge, yet it is indispensable for advancing high-performance photodetectors and beyond. Herein, we report the controlled synthesis of ultrathin, nonlayered β-In2S3 single crystals via an optimized atmospheric pressure physical vapor deposition (APPVD) technique. A precise synthesis window is established, where a temperature of 830 °C and an Ar flow rate of 80 sccm are identified as critical parameters for achieving uniform triangular In2S3 crystals with an ultrathin thickness of ∼1.4 nm. The as-fabricated In2S3-based photodetectors exhibit exceptional performance, achieving a high detectivity of 7.735 × 1012 Jones under 395 nm ultraviolet irradiation, outperforming many existing 2D material-based detectors. Our work not only offers a viable route for scalable production of 2D In2S3 crystals but also confirms its prominent potential for next-generation optoelectronic devices.