Utilizing a NaOH Promoter to Achieve Large Single-Domain Monolayer WS₂ Films via Modified Chemical Vapor Deposition

Because of their fascinating properties, two-dimensional (2D) nanomaterials have attracted a lot of attention for developing next-generation electronics and optoelectronics. However, there is still a lack of cost-effective, highly reproducible, and controllable synthesis methods for developing high-quality semiconducting 2D monolayers with a sufficiently large single-domain size. Here, utilizing a NaOH promoter and W foils as the W source, we have successfully achieved the fabrication of ultralarge single-domain monolayer WS₂ films via a modified chemical vapor deposition method. With the proper introduction of a NaOH promoter, the single-domain size of monolayer WS₂ can be increased to 550 μm, while the WS₂ flakes can be well controlled by simply varying the growth duration and oxygen concentration in the carrier gas. Importantly, when they are fabricated into global backgated transistors, WS₂ devices exhibit respectable peak electron mobility up to 1.21 cm² V^-1 s^-1, which is comparable to those of many state-of-the-art WS₂ transistors. Photodetectors based on these single-domain WS₂ monolayers give an impressive photodetection performance with a maximum responsivity of 3.2 mA W^-1. All these findings do not only provide a cost-effective platform for the synthesis of high-quality large single-domain 2D nanomaterials, but also facilitate their excellent intrinsic material properties for the next-generation electronic and optoelectronic devices.