Estimation of residual carrier density near the Dirac point in graphene through quantum capacitance measurement

摘要

We discuss the residual carrier density (n~*) near the Dirac point (DP) in graphene estimated by quantum capacitance (C_Q) and conductivity (σ) measurements. The C_Q at the DP has a finite value and is independent of the temperature. A similar behavior is also observed for the conductivity at the DP, because their origin is residual carriers induced externally by charged impurities. The n~* extracted from C_Q, however, is often smaller than that from σ, suggesting that the mobility in the puddle region is lower than that in the linear region. The C_Q measurement should be employed for estimating n~* quantitatively.