Influence of the density of states of graphene on the transport properties of graphene/MoS_2/metal vertical field-effect transistors

摘要

We performed detailed studies of the current-voltage (I-V) characteristics in graphene/MoS_2/metal vertical field-effect transistors. Owing to its low density of states, the Fermi level in graphene is very sensitive to its carrier density and thus the external electric field. Under the application of a bias voltage V_B between graphene and the metal layer in the graphene/MoS_2/metal heterostructure for driving current through the van der Waals interface, the electric field across the MoS_2 dielectric induces a shift in the Fermi level of graphene. When the Fermi level of graphene coincides with the Dirac point, a significant nonlinearity appears in the measured I-V curve, thus enabling us to perform spectroscopy of the Dirac point. By detecting the Dirac point for different back-gate voltages, we revealed that the capacitance of the nanometer-thick MoS_2 layer can be determined from a simple DC transport measurement.