Simulation of Inelastic Electron Tunnelling Spectroscopy on Different Contact Structures in 4,4'-Biphenyldithiol Molecular Junctions

A first-principles computational method is developed to study the inelastic electron tunnelling spectroscopy (IETS) of 4,4'-biphenyldithiol molecular junction with three different contact structures between the molecule and electrodes in the nonresonant regime. The obtained distinct IETS can be used to resolve the geometrical structure of the molecular junction. The computational results demonstrate that the IETS has certain selection
rule for vibrational modes, where the longitudinal modes with the same direction as the tunnelling current have greatest contribution to the IETS. The thermal effect on the IETS is also displayed.