Physisorption doping induced multiple dots behavior in graphene nanoconstrictions

We report the single carrier transport properties in the p-doped/less-doped graphene nanoconstriction structures. In the doped graphene devices, the overlapped Coulomb diamond characteristics are observed around the charge neutrality point (CNF) at 5 K. Reducing doping in graphene by annealing, the periodic peaks appear in the certain gate voltage range around the CNP. Additionally, the non-overlapped Coulomb diamond characteristic is observed. These results suggest that unintentional charging island formation in graphene nanodevices can be avoided by decreasing the doping concentration.