Figure 3
(a) The carrier density as a function of the modified gate voltage measured from the charge neutrality point. The blue line is the second order polynomial fitting curve assuming the quantum capacitance of graphene is much smaller than the double-layer capacitance. And the red line is the fitting curve taking the contribution of the electric double-layer capacitance into account. (b) The total capacitance and the quantum capacitance of the graphene sheet calculated using the fitted double-layer capacitance. Both curves show a typical “V”-form.
