Tuning the transport properties of a (C60)2 bridge with electron and hole dopings

The tuning effects of substitutional B and N dopings on the electron transport properties of a C(60) dimer bridge [(C(60))(2)] are investigated by nonequilibrium Green's functions in combination with density functional theory. It is found that, unlike C(60), the equilibrium conductance of (C(60))(2) is very small. However, it can be controlled by electron (N) doping or hole (B) doping, which shifts the molecular energy levels so that the LUMOs or HOMOs align well with the Fermi level and results in LUMO-mediated transport or HOMO-mediated transport. The conductance increases accordingly with a certain number of N or B atoms doped in the C(60)s. Interestingly, when one C(60) is doped with N atoms and the other is doped with B atoms, new transport behaviors arise and rectification is achieved due to the special alignment of the energy levels of the individual C(60)s with the Fermi level. It suggests that cluster or molecule assembling can often realize specific functions which are not available by single molecules and should be taken into consideration in the design of molecular devices.