Gate-Assisted Programmable Molecular Doping of Epitaxial Graphene Devices

Since the discovery of graphene, control of its carrier density via doping or functionalization has been a crucial need. Despite significant progress, precise control of the carrier density for epitaxial graphene on SiC remains a challenge. Multiple cycles of doping and characterization are often required before achieving a desired carrier density. In this work, a new approach is demonstrated to precisely program the doping level in top-gated epitaxial graphene devices that are exposed to nitric acid vapor before the gate deposition. With the help of an applied gate voltage, the modification of carrier concentration introduced by the nitric acid can be reversibly controlled, while the corresponding carrier density at zero gate voltage can be accurately tuned by more than 4 × 10¹³ cm^-2 across the charge neutrality point. This gate-assisted molecular doping enables tuning of the charge neutrality point to the desired gate voltage value and can be stabilized by cooling the sample below 200 K.