Effects of Interface Roughness on Electronic Transport Properties of Nanotube−Molecule−Nanotube Junctions

We investigate electronic transport properties of molecular junctions constructed by a single conjugated molecule attached in the gap of two broken metallic single walled carbon nanotubes (CNTs). With the help of molecular dynamic simulations (MD), we have provided a realistic description for mechanical stretching processes of different carbon nanotubes and contact structures between the broken CNTs and the conjugated molecule in different junctions. Statistical analysis shows that the molecule generally prefers to be titled inside the junctions with polygonal contact, in particular the apex at the broken ends of tubes. Nonequilibrium Green’s function (NEGF) calculations reveal that such realistic CNTs-molecular junctions have very different electron transport properties from junctions with ideal SWCNTs as electrodes. The statistically and energetically favorable CNTs-molecular junctions of different chiralities are found to be always metallic, but their absolute conductance is sensitive to the chirality of the tube. It is suggested that with armchair CNTs as electrodes, a better conductivity can be obtained. The calculated current−voltage characteristics of junctions with realistic contact geometries are in good agreement with experiments.