Effect of hydrogen concentration on CVD synthesis of graphene

The paper is devoted to the study of AP-CVD synthesis of graphene on a copper substrate. In this work, the effect of hydrogen concentration in the synthesis gas mixture on the growth of a graphene coating is studied experimentally. Two series of experiments with methane concentrations of 0.02% and 0.05% are presented. It is shown that a change in concentration of hydrogen has a nonmonotonic effect on the degree of substrate covering with graphene. This indicates that hydrogen is involved in several competing processes. One of these processes is stabilization of the edges of growing graphene domains. Another is etching of the forming graphene structures and reduction of hydrocarbon radicals on the copper substrate surface and in the bulk. It is shown that an increase in methane concentration leads to an increase in the rate of graphene crystal growth. To preserve the kinetics of graphene domain growth, it is necessary to reduce the H₂/CH₄ coefficient in the working mixture. (paper)