Effects of Proton and X-ray Irradiation on Graphene Field-Effect Transistors with Thin Gate Dielectrics

Charge pumping and drain current-gate voltage ( I_D- V_G) measurements are used to investigate degradation and environmental effects in X-ray and proton-irradiated graphene transistors. X-ray irradiation initially degrades mobility due to hole trapping in the oxide, and induces oxygen-related p-type doping that is evident in the increase in ID once trapped holes anneal out; after long times, interface trap buildup dominates device response. Both the drain current and charge pumping current decrease initially after proton irradiation due to displacement damage and dedoping. However, continued degradation indicates further damage to the graphene layer itself, likely from oxygen-related defect creation in the graphene, induced water and gas molecules between the graphene layer and underlying substrate, or some combination of both. These results indicate that the environment can significantly affect the radiation response of graphene devices, and that the long-term response of the device may be quite different from the initial response due to defect creation, charge migration and annealing.