Using the quantum capacitance in graphene to enable varactors for passive wireless sensing applications

A wireless sensor concept based upon the quantum capacitance effect in graphene is described. By utilizing thin gate dielectrics (EOT <; 2 nm), the capacitance in a metal-insulator-graphene structure varies with charge concentration through the quantum capacitance effect. The high capacitance per unit area allows orders of magnitude improvement in scalability compared to MEMS-based sensors, while the high mobility in graphene allows high quality factors, Q, to be obtained. When operated away from the Dirac point, simulations using realistic structural and transport parameters predict capacitance tuning ratios of >; 4 and Q values >; 30 at 1 GHz. When operated at the Dirac point, the capacitance shows a strong temperature sensitivity, suggesting potential applications as a wireless temperature sensor.