Mixed-Salt Enhanced Chemical Vapor Deposition of Two-Dimensional Transition Metal Dichalcogenides

The usage of molten salts, for example, Na₂MoO₄and Na₂WO₄, has shown great success in the growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD). In comparison with the halide salt (i.e., NaCl, NaBr, and KI)-assisted growth (Salt 1.0), the molten salt-assisted vapor-liquid-solid growth technique (Salt 2.0) has improved the reproducibility, efficiency, and scalability of synthesizing 2D TMDCs. However, the growth of large-area MoSe₂and WTe₂is still quite challenging with the use of the Salt 2.0 technique. In this study, a renewed Salt 2.0 technique using mixed salts (e.g., Na₂MoO₄-Na₂SeO₃and Na₂WO₄-Na₂TeO₃) is developed for the enhanced CVD growth of 2D MoSe₂and WTe₂crystals with a large grain size and yield. A continuous monolayer MoSe₂film with a grain size of 100-250 μm or isolated flakes up to ∼450 μm is grown on a halved 2 inch SiO₂/Si wafer. Our study further confirms the synergistic effect of Na⁺and SeO₃^2-in the enhanced CVD growth of the wafer-scale monolayer MoSe₂film. Thus, the addition of Na₂SeO₃and Na₂TeO₃into the transition metal salts could be a general strategy for the enhanced CVD growth of many other 2D metal selenides and tellurides.