New insight into the growth of monolayer MoS2 flakes using an indigenously developed CVD setup: a study on shape evolution and spectroscopy

Monolayer MoS2 has received special consideration owing to its intriguing properties and its potential to revolutionize modern technologies. Atmospheric pressure chemical vapor deposition (APCVD) is the traditional method to grow uniform and high-quality MoS2 flakes in a controlled manner. Little is known, however, about their synthesis mechanism and shape evolution. Herein, we report the synthesis of monolayer MoS2 flakes at atmospheric pressure using a home-built CVD setup. A wide range of shapes are grown from triangular shapes to many point stars, via in-between shapes such as four and six-point stars, using the weight ratio variation of MoO3 and S precursors at different growth temperatures. Further, the properties of the as-grown MoS2 flakes are probed by optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Raman spectroscopy, photoluminescence (PL), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS), confirming that they are regular and good in quality. Moreover, the synthesis pathway and different shape formations are explained on the basis of the fluid model and the growing rate of Mo, S zigzag edges. Thus, this work provides a better insight into the synthesis mechanism of monolayer MoS2 and represents a significant step towards realizing potential future applications.