A Two-Dimensional NiS/MoS₂ Metal-Semiconductor Vertical Heterojunction for a Sub-100 nm Transistor

The reliable contact between two-dimensional (2D) semiconducting transition-metal dichalcogenides (TMDCs) and electrodes is the prerequisite for constructing next-generation electronic devices. Despite considerable efforts having been devoted, realizing such a desirable target remains a great challenge due to the complexity of selective doping on 2D semiconducting TMDCs and the physical damage during the metal electrode integration process. Here, we propose a two-step chemical vapor deposition strategy to synthesize 2D metallic NiS with excellent electronic conductivity and robust environmental stability on monolayer MoS₂. The in situ fabricated 2D NiS/MoS₂ vertical heterojunctions possess perfect contacts and intrinsic interfaces, which deliver distinguished device performances featured with a high average carrier mobility (59.8 cm² V^-1 s^-1) and large on/off current ratio. Particularly, due to the improved interface contact, monolayer MoS₂ short-channel transistors exhibit an approximate current saturation under a low drain-source bias (0.9 V) with the on-state current density of 1.20 mA μm^-1, which outperforms the equivalent silicon complementary metal-oxide semiconductor and satisfies the target of the International Roadmap for Devices and Systems. This work contributes to the growth of van der Waals metal-semiconductor heterojunctions and the integration of future 2D electronics.