Alkali Metal-Assisted Growth of Single-Layer Molybdenum Disulfide

We report alkali metal-assisted growth of monolayer molybdenum disulfide (MoS2) by chemical vapor deposition. Single-layer MoS2 flakes with high-quality and large-scale (>∼200 μm) are successfully fabricated on alkali metal-coated SiO2 substrates. On the other hand, particle-like MoS₂ tends to grow on bare SiO₂ substrates. Detailed growth process of layered MoS₂ with surface-coated alkali metal is suggested. A series of experimental and theoretical results indicate that alkali metals play a role in strong surface adsorption and re-supply of molybdenum precursor to the growth surface during lateral growth of MoS₂. We believe that our results will provide fruitful information for large-scale or selective-area growth of single-layered transition metal dichalcogenides.