CVD controlled growth of large-scale WS 2 monolayers.

Monolayer tungsten disulfide (WS 2 ) with a direct band gap of ca. 2.0 eV and stable properties has been a hotspot in two-dimensional (2D) nanoelectronics and optoelectronics. However, it remains challenging to successfully prepare monolayer WS 2 . In this paper, we report the chemical vapor deposition (CVD) growth behavior of hexagonal WS 2 monolayers by using WS 2 powders and sodium triosulfate (Na 2 S 2 O 3 ) as precursors. We observed the Na 2 S 2 O 3 has a significant effect on the WS 2 triangular and leaf-like shapes. In addition, based on proposed S-termination and W-termination theory, the growth mechanisms for different shapes of WS 2 were discussed.