Flow characteristics of low pressure chemical vapor deposition in the micro-channel

Chemical vapor deposition is a method of producing thin films by chemical reactions on the substrate surface. The preparation of semiconductor devices, graphene fiber materials, carbon nanotubes, and other materials by this method involves the reaction of the rarefied gas flows. In this paper, the flow characteristics of two-component dilute gases containing methane and hydrogen are studied by numerical simulation, which also provides an explanation for the experimental phenomena of graphene growth in rarefied conditions. To reveal the reaction mechanism from the perspective of molecular collision effects, the competitive mechanism between the collision effects in the bulk region and on the substrate surface is studied over a wide range of Kn. It is found that the collisions in the bulk region dominate at moderate Kn (0.1–5), while the surface collisions are prevailing at large Kn (Kn > 5). Furthermore, the influence of inlet gas temperature, Kn, and aspect ratio of a single channel on system temperature distribution is also studied. The results show that the temperature distribution is symmetrical for a rarefied system, while it is asymmetric when the system is in the near continuum regime. Furthermore, the change in aspect ratio has little effect on the temperature distribution.