Water‐Assisted Growth of High‐ κ BiOCl Dielectric at Low‐Temperature for 2D Transistors

While 2D high‐ κ dielectrics are promising for extending Moore's Law, their adoption is hindered by limited crystallinity, low dielectric constant, and high‐temperature processing incompatible with back‐end‐of‐line integration. To overcome these challenges, we developed a low‐temperature (170°C) chemical vapor deposition technique to grow single‐crystalline 2D bismuth oxychloride (BiOCl), achieving large‐area flakes with an average edge length of 31.5 µm. The resulting BiOCl‐based metal–insulator–metal devices exhibit a high dielectric constant of 16.9 and a high breakdown field of 11.2 MV cm −1 . When integrated as the gate dielectric in a back‐gated MoS 2 field‐effect transistor, BiOCl enables outstanding electrical performance: an on/off current ratio of 10 8 , a near‐ideal subthreshold swing of 61 mV dec −1 , a low normalized hysteresis of 1.39 × 10 −2 V (MV cm −1 ) −1 at 0.04 V s −1 , a field‐effect mobility of 17.9 cm 2 V −1 s −1 , and a low interface trap density of 5.82 × 10 10 cm −2 eV −1 . The devices also show robust stability, with no degradation in the on/off ratio and only a slight threshold voltage shift after 3 months. This work establishes 2D BiOCl as a leading high‐ κ dielectric candidate, offering a practical route to overcoming scaling limits and enabling next‐generation low‐power nanoelectronics.