A feasible approach to fabricate two-dimensional WS2 flakes: From monolayer to multilayer

Tungsten disulfide (WS2), with indirect-direct bandgap transition when thinned down to atomically thin flake, provides intriguing applications in next-generation optoelectronics. Here, we develop a feasible approach to fabricate two-dimensional (2D) WS2 flakes by the evaporation and sulfurization of W film using S powder. The layer number and lateral dimension of the as-grown WS2 flakes are confirmed by Raman spectroscopy, photo-luminescence (PL), optical microscopy, and atomic force microscopy (AFM). The evolution of the layer number and edge length of the flakes is attributed to the concentration gradient of W vapor on the substrate surface in the atmosphere. Our result opens a novel pathway to fabricate other 2D transition metal dichalcogenides (TMDs) and construct 2D TMDs-based heterostructures.