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Charge transport through nanocontacts

The present chapter deals with the charge transport phenomena through different nanocontacts, involving pristine and doped/defective graphenes and molecular contacts formed by single molecules anchored in between metal surfaces. We discuss on the basic principles of mesoscopic charge transport, experimental and theoretical procedures and present some important results that we have obtained from first principle calculations. We also provide a brief review on the concerned area. For the graphene-based contacts, we put emphasis on the doped and defective graphene nanoribbons of different edge-symmetries and edge-passivations. Some nanocontacts have been formed by molecular pentacene, Ni-bis(dithiolene) complexes, carbon atomic nanowires, etc. The observed phenomena such as negative differential resistance, Schottky contact, etc. have been correlated with the electronic structures of the molecules and the graphene leads. The edge-states of graphene have been shown to have a great impact on the charge transport properties of the nanojunctions. The molecular contacts have been studied to show the conductance and carrier switching involving them. We have shown how stereoelectronic effects can lead to conductance switching in some specified σ-conjugated oligosilanes. Effects of conjugation length and chemical substitution have been shown to provide charge carrier switching in some nanojunctions.