The Effect of Photon-induced Hot-electron on Tunneling Efficiency across Nanojunctions

The fundamental of molecular electronics involves electron-transport through electrode-molecule-electrode junctions. The transporting efficiency can be correlated to barrier height by tunneling decay constant. The interaction of molecular electronics with plasmons, collective oscillations of free electrons coupling to electromagnetic fields, has drawn lots of attentions. The formation of hot electrons from surface plasmon decay results in photocurrent. In addition, hot electron can also be generated from photoexcitation. We measure the tunneling phenomenon without molecules bridging between electrodes and the responses of gold and silver electrodes, solvent including octylbenzene and propylene carbonate, and electromagnetic field to tunneling decay constant by scanning tunneling microscopy break junction (STM BJ). The tunneling decay constant is reduced for silver electrodes in propylene carbonate when irradiated, that would be realized by comparing the work function of metal, polarity of solvent and by the presence of hot electrons. Following the concept of hot electrons, we investigate the increased conductance of molecules that binding to Au electrodes via head group under illumination and explain the differences in the conductance enhancement of 2,7-diaminofluorene and 4,4′-bipyridine.