Conductance and I-V characteristics of Au/BPY/Au single molecule junctions

Abstract

We have investigated the low bias conductance and I-V characteristics of single 4,4′-bipyridine (BPY) molecule connected to gold electrodes at room temperature. Exploiting the mechanical controllable break junction technique we statistically determined the most preferred conductance value of Au/BPY/Au single molecule junctions. The measured conductance, 0.01G0 (G0 is the conductance quantum unit), is in good agreement with two of the previous experiments using scanning tunnel microscopy break junctions. The I-V characteristics of the Au/BPY/Au junction have been directly measured by varying the bias up to ±0.5 V while holding the junction at its single molecule state. By comparing the obtained I-V curves with those of the Au/1,4-benzenedithiol (BDT)/Au junction, we observed differences in the energy level alignment of BPY and BDT molecules with respect to the Au electrode.