Atmospheric Pressure Chemical Vapor Deposition Growth of Millimeter-Scale Single-Crystalline Graphene on the Copper Surface with a Native Oxide Layer

Abstract

We show millimeter-scale graphene single crystals synthesized on commercial Cu foils by the atmospheric pressure chemical vapor deposition (CVD) method, which does not involve the routine use of a specially designed CVD reactor or long-term processes. Upon the designed annealing step in the Ar environment, the natural oxide layer covering on Cu catalysts is to a large extent maintained and is further used to protect the surface passivation and restrict the graphene nucleation. Moreover, for Cu foils placing on certain solid supports, we found that the graphene deposition is highly related to the environments proximate to each surface (referred to as open or confined space, respectively). For instance, the domain size of as-grown graphene is larger (smaller), while the nucleation density is higher (lower) on the back (top) surface. The possible mechanism to interpret the discrepancy on either side is discussed in the frame of the graphene nucleation and growth kinetics. At the nucleation stage, the thermal decomposition of the oxide layer leads to oxygen (O) desorption at high temperature on the open side and dominates the temperature dependence of nucleation density. On the confined side, the O desorption is suppressed due to the collision rebound effect, but highly concentrated active carbon species will be trapped in the vicinity of the back surface, which may promote the threshold of nucleation on the O-containing Cu surface. The following growth of graphene islands is edge-attachment limited on both sides of the Cu foil but with different enlargement rates. The roughness of support substrates also affects the deposition of graphene. With an optimized annealing condition and a polished quartz support, ∼3 mm isolated graphene islands with an average growth rate of ∼25 μm/min were obtained. The as-grown hexagonal domains were further confirmed to be uniform, monolayer, single-crystalline graphene with a field-effect mobility of ∼4900 cm2 V–1 s–1 at room temperature.