Minimizing the Water Effect in Synthesis of High-Quality Monolayer MoS₂ Nanosheets: Implications for Electronic and Optoelectronic Devices

Two-dimensional materials are promising building blocks for information technology, energy, and sensing devices. However, controlled synthesis of high crystallinity materials is still a challenge, limiting their further developments. Here, we report the effect of water in synthesizing monolayer MoS2 by chemical vapor deposition. We show that, from both experiments and simulation, the presence of water can reduce the precursor flux and diffusivity, resulting in altered growth kinetics and different morphologies. By using an unglazed crucible approach, the growth can be restored to the kinetic Wulff shape regime, thereby providing high crystallinity monolayer crystals with enhanced reproducibility.