DFT study on the atomic-scale nucleation path of graphene growth on the Cu(111) surface

The nucleation path of graphene growth on the Cu(111) surface is investigated by importing carbon atoms step-by-step using density functional theory (DFT) calculations. An overall path of graphene nucleation has been proposed based on configuration and energy analysis. At the very first stage, linear chains will be formed and dominate the copper surface. Then, Y-type (furcate) carbon species will be shaped when new carbon atoms are absorbed aside the linear chains. Finally, ring-containing carbon species and graphene islands will be formed stepwise, with energetic preference. We find that the Y-type and ring-containing carbon species are not likely formed directly at the initial stage of graphene nucleation, but should be formed starting from linear chains. The nucleation limiting step is the formation of the Y-type species, which must pass an energy barrier of about 0.25 eV. These underlying observations are instructive to stimulate future experimental efforts on graphene synthesis.