An Ab Initio-study of Electron Transport through Nitro- Benzene: the Influence of Leads and Contacts

The modification of chemical functions on conjugated aromatic molecules has been suggested as an enabling tool for implementing data storage [1] and information processing [2] in molecular electronics. Much attention has been devoted to nitro-groups as suitable ligands [2]-[4], since they generate states inside the HOMO-LUMO-gap of a delocalised aromatic π-system. In some cases this results in peaks in the current/voltage curves or so called negative differential resistance (NDR) behaviour. For an explanation of these peaks many mechanisms have been proposed involving inelastic or two-step tunneling processes through the induced states [4]. However, an accurate picture of the electronic structure of the electrode/molecule/electrode junction and its detailed relation to the conductance through the junction has so far not been provided for this type of molecules. Especially the influence, which the nature of the leads and the way they are connected to the molecules has on peaks in the conductance, which can also be found for calculations within a coherent elastic scattering approach [2], has not been studied so far.