Millimeter-Scale Continuous Film of MoS Synthesized Using a Mo, Na, and Seeding Promoter-Based Coating as a Solid Precursor.

While the chemical vapor deposition technique can be used to fabricate 2D materials in a larger area, materials like MoS have limited controllability due to their lack of self-controlling nature. This article presents a new technique for synthesizing a void-free millimeter-scale continuous monolayer MoS film through the diffusion of a well-controlled Mo, Na, and seeding promoter-based coating under a low-pressure N atmosphere. Compared to the conventional method, this technique provides precise control of solid precursors, where MoS grows next to the coating. At 800 °C, the synthesized MoS showed a uniform single-layer MoS film; however, a Na-free coating showed nanoscale voids and poor crystal quality, which are attributed to a higher edge-attachment barrier that slows down the MoS lateral growth. The synthesized MoS with Na-containing solution showed an intense PL peak with a 1.86 eV band gap. Even at the relatively low temperature of 700 °C, compared to the Na-excluded condition, MoS showed almost two times higher area coverage with a comparatively larger crystal size. This finding may assist in the future development of MoS-based electronic and optoelectronic devices such as transistors and photodetectors.