Influence of the density of states of graphene on the transport properties of graphene/MoS2/metal vertical field-effect transistors

摘要

We performed detailed studies of the current-voltage characteristics ingraphene/MoS2/metal vertical field-effect transistors. Owing to its low densityof states, the Fermi level in graphene is very sensitive to its carrier densityand thus the external electric field. Under the application of a bias voltageVB between graphene and the metal layer in the graphene/MoS2/metalheterostructure for driving current through the van der Waals interface, theelectric field across the MoS2 dielectric induces a shift in the Fermi level ofgraphene. When the Fermi level of graphene coincides with the Dirac point, asignificant nonlinearity appears in the measured I-V curve, thus enabling us toperform spectroscopy of the Dirac point. By detecting the Dirac point fordifferent back-gate voltages, we revealed that the capacitance of thenanometer-thick MoS2 layer can be determined from a simple DC transportmeasurement.