CFD Simulation Of Chemical Vapor Deposition Growth Of Graphene

Graphene is a star material of carbon material family. Graphene has attracted great interest because of its unique electronic structure and excellent physical prop-erties. Graphene is expected to be used in high-performance nano-electronic devices, composite materials, field emission devices, sensor, energy storage and other fields. Today the main method of preparing graphene films:micro-mechanical exfoliation of graphite, epitaxial growth on SiC substrates, Ruduction of graphite oxide and the chem-ical vapor depositon method. Among them, graphene growth on metal surface via CVD is promisiong way for large-scale, inexpensive, high-quality graphene production. Cu is currently the most widely used substrate material due to its low carbon solubility and the resulted flexibility for graphene layer number controlMechanisms of graphene growth on Cu substate have been intensively studied the-oretically. However, the studies mainly focus on processes happened on the Cu surface. Gas phase effects have been considered only from a thermodynamic point of view. Few studies on gas phase dynamics in graphene growth on copper substrate. However, some recect studies have suggested that gas phase dynamics is important in graphene growth. The role of the pressure of the reacton chamber in the CVD synthesis of graphene using copper catalysts, on large area thickness uniformity is important. With theoretical analy-sis, gas-phase decompositon reaction of methane in the reaction chamber leading to each of the active species in a non-equilibrium state. From upstream to downstream direc-tion fo the gas flow, the active species concentration is gradually increased, therefore. it observed that the graphene obtained on the copper substrate placed in dow nstream is thicker than in upstream, motivated by these results, we perform a systemtic computa-tional fluid dynamics study on gas-phase dynamics during graphene CVD growth in a horizontal tube furnace.In this work, by using CFD software package FLUENT, we simulate the process of CVD synthesis of graphene using copper substrate and methane as carbon sourse. From the simulation results can be found that when the reaction chamber pressure is in low pressure(625mTorr). the mass transport coefficient of methane is much larger than the surface reaction constant of methane, and there is no concentration gradient of methane near the reaction surface, and concentration of methane near suface is al-most same with concentration fo methane in main How. and the suface deposition rate increases exponentially with temperature increase:when the reaction chamber pres-sure is in atmospheric pressure(101325 Pa), the surface reaction constant of methane is larger than the mass transport of methane, and there is significant concentration gradi- ent of methane near the reaction surface, surface concentration of methane is lowest, and surface depositon rate increases slightly with temperature increase. Therefore, we deduce that when the reaction chamber pressure is in low pressure, graphene growth is limited by surface reaction process; when the reaction chamber pressure is in at-mospheric pressure, graphene growth is limited by mass transport process. Without considering the gas-phase decomposition reactions of methane, the surface deposition rate obtained by simulation from the gas flow upstream to downstream decreases un-der atmospheric pressure(101325Pa), medium pressure(2666Pa), low pressure(83Pa), when reaction walls are placed at seven different position independently or simultane-ously. The simulation result does not match the result from experiment. Therefore, the simulation result illustrates that the gas-phase decomposition reactions of methane is so important in the whole CVD synthesis of graphene from the side.