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. MoS 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 MoS 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 MoSnS ( < 0.5) alloy monolayers. The composition difference results in different growth behaviors; Mo dominated alloys ( < 0.5) exhibit uniform and large size (up to 100 μm) triangular monolayers, while Sn-dominated alloys ( > 0.5) present multilayer grains. The MoSnS ( < 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 MoS-based photodetectors. This work offers new perspectives for precision 2D alloy engineering to improve the optoelectronic performance of TMD-based photodetectors.