Influences of temperature gradient and distance on the morphologies of MoS2 domains

Monolayer molybdenum disulfide (m-MoS2) has attracted significant interest owing to its unique electronic and optical properties. Chemical vapor deposition has been well recognized as one of the preferred methods to prepare MoS2 film. Little is known, however, about the effect of the temperature gradient from MoO3 powder to growth substrate on shape, size evolution and growth mechanism. Herein, by controlling the temperature gradient from the pre-vaporization temperature of MoO3 powder to the pre-nucleation temperature of growth substrate at nucleation stage, the inversive, equal, positive temperature gradient (ITG, ETG and PTG) are originally designed. Additionally, we investigate the morphology variation from monolayer to multilayer domains with the change in the temperature gradient on the basis of classical crystal growth theory and the Antonie equation. Also, the IGT could effectively suppress the nuclei density and facilitate the growth of m-MoS2 domains. The results suggest introducing temperature gradient is a significant way for tuning the morphological evolution and achieving the controllable shape of monolayer MoS2 film. And thus, the conclusion will further lay the foundation for expanding the process window of m-MoS2 growth.