Current transport, gate dielectrics and band gap engineering in graphene devices

In this work, we studied current transport in mono-, bi-and tri-layer graphene. We find that both the temperature and carrier density dependencies in monolayer and bi-/tri-layers are diametrically opposite. These difference can be understood by the different density-of-states and the additional screening of the electrical field of the substrate surface polar phonons in bi-layer/tri-layer graphenes. We also find that silicon nitride can provide uniform coverage of graphene in field-effect transistors while preserving the channel mobility. Using this insulator, we studied field-induced band-gap or band-overlap in graphene with various numbers of layers.