Synthesis of Large-Area Uniform MoS2–WS2 Lateral Heterojunction Nanosheets for Photodetectors

Two-dimensional (2D) transition metal dichalcogenides (TMDs) heterojunctions are the basic building blocks for constructing next-generation optoelectronic devices. However, the controllable synthesis of 2D TMDs lateral heterojunctions still face great challenges because of the difficulty in independently controlling the growth of each monomer material. Herein, we reported a novel synthesis strategy that combines the hydrogen (H2)-triggered one-pot chemical vapor deposition growth with liquid-phase precursor predeposition, which can precisely control the precursor supply, to synthesize 2D MoS2–WS2 lateral heterojunction nanosheets. The growth process consists of two independent stages; uniform MoS2 seed crystals were first grown on sapphire substrate with Mo solution precursor predeposited under argon (Ar) condition, and then H2 was introduced into the growth system to trigger the growth of WS2, allowing WS2 to seamlessly grow around MoS2. By using this approach, large-area MoS2–WS2 lateral heterojunctions with uniform domain size, clean surface, high crystallinity, and narrow interface structure were obtained. Transient absorption spectroscopy indicates that the photocarriers can effectively separate at the heterojunction interface. Moreover, prominent rectification characteristics and sensitive photoresponse were achieved on the heterojunction-based devices. This study provides a reliable method for the controllable synthesis of large-scale 2D heterostructures, which is of great significance for their device applications.