Work function mapping of single-crystal graphene

Kelvin potential force microscopy (KPFM) was used to study the surface potential of single-crystal graphene transferred to silicon dioxide substrate and calculate the work function of single-crystal graphene. It was observed that when graphene on copper substrate was directly scanned, the surface potential distribution of normal graphene appeared to be more disordered compared to that of single-crystal graphene. This feature is used to determine the single-crystal property of graphene grown on copper foil by chemical vapor deposition without transfer. The surface potential of the multilayer graphene area at the nucleation point of single-crystal graphene and the surrounding single-layer area is analyzed. It is found that the work function of the multilayer graphene area is slightly lower than that of the single-layer graphene, which provides guidance for the application of single-crystal graphene and multilayer graphene in field emission.