2D Indium Phosphorus Sulfide (In2P3S9): An Emerging van der Waals High‐k Dielectrics

Abstract 2D van der Waals (vdW) semiconductors hold great potentials for more‐than‐Moore field‐effect transistors (FETs), and the efficient utilization of their theoretical performance requires compatible high‐ k dielectrics to guarantee the high gate coupling efficiency. The deposition of traditional high‐ k dielectric oxide films on 2D materials usually generates interface concerns, thereby causing the carrier scattering and degeneration of device performance. Here, utilizing a space‐confined epitaxy growth approach, the authors successfully obtained air‐stable ultrathin indium phosphorus sulfide (In 2 P 3 S 9 ) nanosheets, the thickness of which can be scaled down to monolayer limit ( ≈ 0.69 nm) due to its layered structure. 2D In 2 P 3 S 9 exhibits excellent insulating properties, with a high dielectric constant ( ≈ 24) and large breakdown voltage ( ≈ 8.1 MV cm −1 ) at room temperature. Serving as gate insulator, ultrathin In 2 P 3 S 9 nanosheet can be integrated into MoS 2 FETs with high‐quality dielectric/semiconductor interface, thus providing a competitive electrical performance of device with subthreshold swings (SS) down to 88 mV dec −1 and a high ON/OFF ratio of 10 5 . This study proves an important strategy to prepare 2D vdW high‐ k dielectrics, and greatly facilitates the ongoing research of 2D materials for functional electronics.