Chemical Vapor Deposition of 4 Inch Wafer-Scale Monolayer MoSe₂

2D semiconducting transition metal dichalcogenides (TMDs) are considered promising building blocks for emergent electronic and optoelectronic devices. As one of the representatives of 2D semiconductors, monolayer MoSe₂ has excellent electrical and optical properties and has attracted a lot of research interest recently. To realize various device applications, large-scale synthesis of monolayer MoSe₂ with high crystal quality is critical, yet remains challenging. Herein, the growth of monolayer MoSe₂ at a 4 inch wafer-scale by chemical vapor deposition is demonstrated. Based on a multisource design and vertical placement of substrates, wafer-scale continuity and uniformity of layer thickness, e.g., the monolayer, are achieved. This growth technique is also applicable to the wafer-scale growth of other 2D semiconductors such as WS₂ and MoS₂.