Band gap estimation in bilayer graphene through quantum capacitance measurement

The estimation of the quantum capacitance ($C_{Q})$ through the capacitance measurement provides the direct information on Density of states (\textit{DOS}) in graphene since the energy cost to induce carriers is introduced as $C_{Q}=e^{2}$\textit{DOS} in series with the geometrical capacitance ($C_{ox})$ in the equivalent circuit (1/$C \quad =$ 1/$C_{ox} \quad +$ 1/$C_{Q})$. For bilayer graphene with Y$_{\mathrm{2}}$O$_{\mathrm{3}}$ topgate structure, the band gap opening was qualitatively observed in DOS - energy relation estimated from $C_{Q}$ under the large displacement. The band gap determined by C$_{\mathrm{Q}}$ was larger than the transport gap determined by variable-range hopping in gap states on IV measurement since carriers which respond to the alternating voltage are not required to transport throughout the device.