LAUSR

Growth of large-area uniform and high-quality monolayer transition metal dichalcogenides (TMDs) for practical and industrial applications remains a long standing challenge. Present study demonstrates a modified pre-deposited CVD process by employing an annealing procedure before sulfurization, which help to achieve large-area, highly uniform and high-quality TMDs on various substrates. The annealing procedure resulted in a molten liquid state of the precursors in CVD process, which not only facilitated a uniform redistribution of the precursor on the substrate (avoid the aggregation) because of the uniform redistribution of the liquid precursor on the substrate, but more importantly avoided the undesired multilayer growth via the self-limited lateral supply precursors mechanism. 2-inch uniform and continuous monolayer WS2 film has been synthesized on the SiO2/Si substrate. Moreover, uniform monolayer WS2 single crystals can be prepared on more general and various substrates including sapphire, mica, quartz and Si3N4 under the same growth procedure. Besides, this growth mechanism can be generalized to synthesize other monolayer TMDs such as MoS2 and MoS2/WS2 heterostructure. Hence, the present method provides a generalized attractive strategy to grow large-area uniform single layer 2D materials. This study has significant implication in the advancement of batch production of various 2D materials based devices for industrial and commercial applications.