CVD controlled growth of large-scale WS₂ monolayers

Monolayer tungsten disulfide (WS₂) 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 WS₂. In this paper, we report the chemical vapor deposition (CVD) growth behavior of hexagonal WS₂ monolayers by using WS₂ powders and sodium triosulfate (Na₂S₂O₃) as precursors. We observed the Na₂S₂O₃ has a significant effect on the WS₂ triangular and leaf-like shapes. In addition, based on proposed S-termination and W-termination theory, the growth mechanisms for different shapes of WS₂ were discussed.