  Understanding the atomistic mechanism in graphene growth is crucial for
controlling the number of layers or domain sizes to meet practical needs. In
this work, focusing on the growth of graphene by chemical vapor deposition on
copper substrates, the surface kinetics in the growth are systematically
investigated by first-principles calculations. The phase diagram, predicting
whether the growth mode is monolayer graphene or bilayer graphene under various
experimental conditions, is constructed based on classical nucleation theory.
Our phase diagram well illustrates the effect of high hydrogen pressure on
bilayer graphene growth and clarifies the mechanism of the most widely used
experimental growth approaches. The phase diagram can provide guidance and
predictions for experiments and inspires the study of other two-dimensional
materials with graphene-like growth mechanisms.
