On the Role of Vapor Trapping for Chemical Vapor Deposition (CVD) Grown Graphene over Copper

The role of sample chamber configuration for the chemical vapor deposition of graphene over copper was investigated in detail. A configuration in which the gas flow is unrestricted was shown to lead to graphene with an inhomogeneous number of layers (between 1 and 3). An alternative configuration in which one end of the inner tube (in which the sample is placed) is closed so as to restrict the gas flow leads a homogeneous graphene layer number. Depending on the sample placement, either homogeneous monolayer or bilayer graphene is obtained. Under our growth conditions, the data show local conditions play a role on layer homogeneity such that under quasi-static equilibrium gas conditions not only is the layer number stabilized, but the quality of the graphene improves. In short, our data suggests vapor trapping can trap Cu species leading to higher carbon concentrations, which determines layer number and improved decomposition of the carbon feedstock (CH 4 ), which leads to higher quality graphene.