Growth Mechanism and Influences from Kinetic Factors on Carbon Materials with Cu and Silica Substrates during Atmospheric Pressure Chemical Vapor Deposition

Abstract

High-quality graphene and amorphous pyrolytic carbon are deposited on Cu and silica, respectively, by atmospheric pressure chemical vapor deposition (APCVD). Growth mechanisms and influences from varied kinetic factors on the two products are analyzed and discussed. The gas-phase reaction is the decisive factor for the growth of pyrolytic carbon on silica because of poor catalytic dehydrogenation of the substrate (the electron structure of silica is the fundamental reason), while the surface reaction plays a determining role in the deposition of graphene on Cu. The formed graphene efficiently separates the substrate and aromatic hydrocarbons (AHs, gaseous products) to avoid the deposition of amorphous carbon on Cu. High H2 concentration acts as a kinetic inhibitor for both products. For the Cu substrate, H2 competes with CH4 to occupy surface active sites because of its high solubility in Cu. Moreover, excess H atoms decrease graphene quality by acting as a core for the formation of sp3 bonded carbon atoms. As for the silica substrate, the presence of H2 depresses the gas reaction, reduces the amount and size of the AHs, and leads to a lower deposition rate. In addition, the relationship between deposition rates of carbon materials and kinetic factors are studied.