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

Abstract

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