We present our observations made during the early stages of graphene growth employing an ethylene-based CVD method capable of synthesizing copper-foil-catalyzed monolayer graphene at temperatures as low as 800°C. Spectroscopic monitoring of surface catalysis showed that graphene crystals evolve from densely distributed nucleation points that interconnect to form large crystals covering the entire surface. Secondary nucleation was observed inside the primary graphene crystals. An effective activation energy for copper-catalyzed ethylene-based graphene synthesis was determined to be 2.46 eV, a value that suggests surface dehydrogenation of ethylene or lattice integration of graphene as the possible rate-determining step in the heterogeneous catalysis.
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