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Two-dimensional materials, including transition-metal dichalcogenides (TMDs), have aroused wide interest due to their various applications in gas sensors and photoelectric devices. However, achieving a uniform distribution of materials on the substrate is still a challenging and urgent problem. In this article, the factors influencing the material distribution during the chemical vapor deposition process are investigated by a simulation method, and the results show that the unequal velocity distributions caused by the carrier gas flow on the growing surface play an important role in influencing the crystal distribution. Boundary layer theory is used to explain the mechanism of the effect of the carrier gas flow on the growth uniformity. An improved method is proposed to improve the material uniformity by changing the placement of the Si/SiO2 substrate from face down to face up. The simulation and experimental results show that uniformly distributed MoS2 with a large size and good quality can be obtained with the improved method. This work provides a method for preparing uniformly distributed TMDs on a substrate, which should facilitate subsequent research of two-dimensional materials and promote the application of two-dimensional materials.

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