Large-area high quality MoS2 monolayers grown by sulfur vapor counter flow diffusion

Abstract

Large-area uniform monolayer MoS₂ films are prepared via an atmospheric pressure chemical vapor deposition method. Sulfur vapor counter flow diffusion lowers its concentration at the reaction zone and makes MoO₃ sulfurization slow and gentle, which is beneficial for monolayer MoS₂ growth. Suboxide MoO_3−x domains, co-existing MoS₂ mono- and multi-layers, monolayer MoS₂ films, triangular MoS₂ monolayer flakes are successively formed in the growth zone along the gas flow direction. Optical microscopy, atomic force microscopy, transmission electron microscopy, UV-vis, Raman and photoluminescence spectra demonstrate that the as-grown films are continuous monolayers over a large area, and are of high quality comparable to exfoliated monolayer MoS₂. This method can also be applied to synthesize MoS₂/MoO₂ microplates without the assistance of metal oxides.