The Repeatability and Reproducibility Problem in the CVD Synthesis of 2D Materials: Towards a More Efficient and Sustainable Synthetic Process

Though Chemical Vapor Deposition (CVD) is a versatile process that has been widely used for synthesizing graphene, hexagonal boron nitride (h BN) and other 2-D materials, the process is plagued by issues of repeatability and reproducibility, the two important pillars of the scientific method. The primary reason for this is that we do not know or can directly measure the reaction environment inside the reactor (flow and thermal fields and reactant concentrations) that controls the growth process and the final film characteristics. In turn, we are unsure about the external parameters that control this reaction environment and can be measured instead. Consequently, experimental details currently monitored and reported in the literature are insufficient to ensure reproducibility, with process details typically reported only partially, and details about the reactor not included at all, further compounding the problem. In this paper, using the example of a hot-wall tube reactor that is typically used in the laboratory and the Computational Fluid Dynamics toolbox OpenFOAM, we have simulated the reactor environment and identified measurable reactor and process parameters that control this environment and explored its sensitivity to these external parameters. Based on our findings, we have devised a straightforward protocol for experimentalists to use for monitoring and reporting CVD processes in literature so that they become repeatable and reproducible, and, aid in analyzing and studying processes and mechanisms, rapid testing of ideas, process scale-up and an overall faster and more sustainable progress of the field.