Figure 3.
CEDL obtained from direct AC measurement (a), Schematic side view of a device for capacitance measurement and the equivalent circuit. Materials and terminal configurations are indicated. RIL and Rgr are the electric resistance in the ionic liquid and graphene, respectively. CPt is the capacitance between Pt wire and the ionic liquid. Actual size of Pt wire (100 μm in diameter) is much larger than the square window (15 μm on a side), but it is depicted as a thin wire in the figure for clarity. Optical microscope image of a sample is also indicated. Scale bar shows 20 μm. (b), Vtg dependence of CEDL for 6-layer graphene. The gate voltage was swept from negative to positive values.