Growth mechanism and controllable synthesis of graphene on Cu–Ni alloy surface in the initial growth stages

• The adsorption and migration ability of C can be controlled by substrate alloying.
• The energy barriers of C dimerization depend on the proportions of Cu–Ni alloy.
• Alloyed substrates can prevent the self-limiting effect of graphene film growth.

Catalytic chemical vapor deposition (CVD) on transition metals is a promising and versatile technique for graphene (and graphene film) growth. Recently, substrate alloying has been used to improve graphene synthesis by CVD. However, the underlying mechanism is still elusive. In this work, taking the Cu–Ni alloy surface as an example, we study the mechanism of carbon nucleation on the alloy surface in the initial stages using first-principles calculations. The energetics and kinetics of C-dimer formation are considered. Our calculations reveal that substrate alloying may strongly affect the carbon dimerization in CVD synthesis. Both the adsorption strength of C species and the dimerization barriers vary with the alloy composition. In addition, carbon migration, an important step in graphene growth, can also be controlled by alloying. Our findings may provide an understanding of the mechanisms by which alloying controls graphene (and graphene film) growth in CVD.