High quality factor graphene varactors for wireless sensing applications

A graphene wireless sensor concept is described. By utilizing thin gate dielectrics, the capacitance in a metal-insulator-graphene structure varies with charge concentration through the quantum capacitance effect. Simulations using realistic structural and transport parameters predict quality factors, Q, 60 at 1 GHz. When placed in series with an ideal inductor, a resonant frequency tuning ratio of 25 (54) is predicted for sense charge densities ranging from 0.32 to 1.6 μC/cm² at an equivalent oxide thickness of 2.0 nm (0.5 nm). The resonant frequency has a temperature sensitivity, df/dT, less than 0.025/K for sense charge densities 0.32 μC/cm².