Na-assisted fast growth of large single-crystal MoS₂ on sapphire

Monolayer molybdenum sulfide (MoS₂), a typical semiconducting transition metal dichalcogenide, has emerged as a perfect platform for next-generation electronics and optoelectronics due to its sizeable band gap and strong light-matter interactions. Nevertheless, the controlled growth of a monolayer MoS₂ single-crystal with a large-domain size and high crystal quality still faces great challenges. Herein, we demonstrate the fast growth of a large-domain monolayer MoS₂ on the c-plane sapphire substrate with the assistance of sodium chloride (NaCl) crystals as the intermediate promoter. Particularly, the volatilization temperature of the NaCl crystal and the growth temperature of MoS₂ are established to be the key parameters that influence the growth efficiency of MoS₂ at an optimized growth condition. Monolayer triangular MoS₂ domain with an edge length ∼300 μm is obtained within 1 min, featured with a growth rate ∼5 μm s^-1. The Na element from the NaCl crystal is found to be able to facilitate the two dimensional growth of monolayer MoS₂. This work thus offers novel insights into the high-efficiency production of large-domain monolayer MoS₂ on insulating growth substrates.