Two-Dimensional Alloying Molybdenum Tin Disulfide Monolayers with Fast Photoresponse

Elemental alloying in monolayer, two-dimensional (2D) transition metal dichalcogenides (TMDs) promises unprecedented ability to modulate their electronic structure leading to unique optoelectronic properties. MoS₂ monolayer based photodetectors typically exhibit a high photoresponsivity but suffer from a low response time. Here we develop a new approach for Sn alloying in MoS₂ monolayers based on the synergy of the customized chemical vapor deposition (CVD) and the effects of common salt (NaCl) to produce high-quality and large-size Mo_1-SnS₂ (x < 0.5) alloy monolayers. The composition difference results in different growth behaviors; Mo dominated alloys (x < 0.5) exhibit uniform and large size (up to 100 μm) triangular monolayers, while Sn-dominated alloys (x > 0.5) present multilayer grains. The Mo_1-SnS₂ (x < 0.5) based photodetectors and phototransistors exhibit a maximum responsitivity of 12 mA/W and a minimum response time of 20 ms, which is faster than most reported MoS₂-based photodetectors. This work offers new perspectives for precision 2D alloy engineering to improve the optoelectronic performance of TMD-based photodetectors.