In-situ monitoring of AuCl₃-doping and -dedoping behaviors in graphene

In-situ variations of the surface morphology, transmittance, sheet resistance, and Dirac curve of graphene have been monitored during AuCl₃-doping and annealing-induced-dedoping processes. The transmittance of graphene shows a monotonically-decreasing behavior due to doping and subequent annealing at higher temperatures (T_A), resulting from the continuing increase in the surface corrugations due to intensified coalescing of Au clusters. Electronic parameters, such as the sheet resistance, work function, Dirac point, and electron mobility, show their extreme values when annealed at 50 °C after doping, which can be attributed to further enhancement of a reaction donating electrons to Cl ions from graphene at T_A = 50 °C. The annealing at higher T_A induces a dedoping effect due to the Cl desorption, thereby decreasing the doping efficiency. These results suggest that Cl anions play a crucial role in the doping and the dedoping processes, especially causing variations in the electronic properties of graphene.