Morphological Evolution of Monolayer MoS2 Single-Crystalline Flakes

This is the authors' abstract. We don't add key points for this paper.

Understanding and controlling the growth morphology of two-dimensional crystals of transition metal dichalcogenides (TMDs) is essential in developing high-quality crystalline material for spintronics, valleytronics, electronics, and optics. Here we report our studies on the evolution of crystallite morphology of MoS 2 observed in chemical vapor deposition. It is shown that as time goes on, the growth morphology of MoS 2 flakes undergoes a transition from a triangle to a star shape, then back to a triangle, and finally to a bulgy irregular morphology. By tuning the temperature of the element sources, the atomic ratio of S and Mo on the growing interface can be adjusted. The variation of the S/Mo ratio affects the edge diffusion length and nucleation behavior on the edge of crystallite, leading to different growth morphologies. Our observations provide clues on how to engineer the morphology and control the quality of TMD crystalline sheets.