Single crystal monolayer MoS₂ triangles with wafer-scale spatial uniformity by MoO₃ pre-deposited chemical vapor deposition

Two-dimensional transition metal dichalcogenides (TMDs) show a potential application in photoelectric device due to their excellent electrical and optical properties. Here, we report that the MoO₃ pre-deposited chemical vapor deposition (CVD) is used to synthesize single crystal monolayer MoS₂ triangles on 4 in. wafer. We found that the wafer-scale uniformity of MoS₂ can be greatly improved by regularly depositing MoO₃ particles on substrate before CVD growth. Therefore, a piece of cleanroom wiper was used as a template for implementing precise control of MoO₃ pre-deposition. We found that the optimal deposition size of MoO₃ particles and the distance between MoO₃ particles are about 15 μm and 0.9 mm, respectively. Both microscopic and spectroscopic characterization results demonstrate that the as-grown MoS₂ is highly uniform in space distribution and crystal structure. The electronic performance of MoS₂ synthesized by our method is comparable to or even slightly better than those in common CVD samples. The role of MoO₃ pre-deposition is not only to effectively control the MoS₂ nucleation density but also to overcome poor diffusion of MoO₃ source. Our method is expected to accelerate the industrial synthesis of the atomically thin TMD materials.