NaCl-Assisted CVD Growth of Large-Area High-Quality Trilayer MoS 2 and the Role of the Concentration Boundary Layer

Direct growth of wafer-scale high-quality 2D-layered materials (2DLMs) on the SiO 2 /Si substrate is still a challenge. The chemical vapor deposition (CVD) technique has shown a significant role in achieving a large-area continuous film of 2DLMs. CVD growth requires the optimization of several growth parameters, namely, temperature, amount of precursors, pressure, carrier gas flow, and distance between the reactants. However, the role of the boundary layer of reactant concentration has not been explored yet. The amount of precursors which leads to the formation of the reactant concentration boundary layer has a noteworthy impact in controlling the thickness of the growing material. Here, we report the role of the concentration boundary layer to achieve large-area MoS 2 in NaCl-assisted CVD growth at low temperature. Control of boundary layer thickness has led to the synthesis of monolayer, bilayer, trilayer, and bulk MoS 2 films and flakes in our single-zone CVD at atmospheric pressure. We believe that our approach may lead to synthesize other wafer-scale 2DLMs that will pave the way for nano- and optoelectronics.