Abstract: Graphene has a significant advantage that its carrier density can be easily tuned. Various methods for controlling carrier density have been proposed, of which gate tuning is the most widely used. However, in practical applications, gate tuning also has some limitations. For example, some designed circuits and test instruments cannot stand high voltages over hundreds or even tens of volts. Recently, a method of doping with electron beam irradiation has appeared, which can change graphene carrier density locally and continuously, but the tuning range is small. Here a new mixed doping route combining HNO3 doping and electron beam irradiation was presented, which shows greater ability to tune carrier density continuously in a larger range. By analyzing the results of the scanning near-field optical microscope and electrical transport, it was found that the mixed doping route adjusts the graphene carrier density from 2.15×103 cm-2 to -1.49×102 cm-2,which is equivalent in tuning effect to 320 V for gate tuning of the 300 nm silicon dioxide.In addition, graphene can be written into pre-designed electric patterns via electron beam irradiation, which is potentially widely applicable.

Key words: electron beam irradiation, HNO3 doping, local doping, mixed doping, density carrier