Modeling Extreme Rapid Thermal Processing in Chemical Vapor Deposition Reactors for Catalytic Growth of Carbon Nanotubes.

Chemical vapor deposition (CVD) reactors with rapid thermal processing (RTP) capabilities provide unique advantages for controlling nanomaterial synthesis. Hence, understanding the dynamics and spatial distribution of the temperature inside them is key for process control as well as for engineering the resulting structure and properties. We use the finite element method (FEM) to model the spatiotemporal evolution of temperatures inside a custom-designed extreme multizone reactor for CVD of carbon nanotubes (CNTs) and graphene with RTP capabilities. Heat is primarily generated by 12 infrared (IR) lamps distributed both above and below a quartz tube in the reaction zones. Radiation is modeled by using the Monte Carlo radiation model. A catalyst-coated silicon chip is placed on a quartz support in the middle of the reactor. A thermocouple is modeled as a composite, where an area-weighted average of all the components was used to determine bulk properties. A mesh convergence study consisting of three refinements was carried out to ensure proper mesh size, leading to a model with 1.4 million elements. The model was then validated by comparing simulations to experimental data relating the infrared lamp power-to-temperature rise dynamics measured by the thermocouple. Results show that our model adequately captures the extreme temperature transience in the reactor and can hence be used to accurately explain the influence of boundary conditions on the spatial distribution of temperatures as well as the kinetics of heating of both the thermocouple and the catalyst-coated chip. Accordingly, the model is powerful for the design of new support wafer geometries and materials to precisely control the temperature distribution to achieve unprecedented spatial control in nanocarbon synthesis.