Vibrational spectra of metal-molecule-metal junctions in electromigrated nanogap electrodes by inelastic electron tunneling

Abstract

We measure the vibrational signatures of metal-molecule-metal junctions formed from 1,8-octanedithiol and 1,4-benzenedithiol incorporated into electromigrated nanogap electrodes using inelastic electron tunneling spectroscopy (IETS). The junction conductance measured suggests that the IETS spectra have been achieved at the individual molecule level. The IETS spectra provide unambiguous experimental evidence of the existence of the component molecules in the fabricated nanogap electrode testbeds. The intense Au-S stretch peaks elucidate that the thiol anchor group is linked to the broken Au wires during electromigration, thus creating reliable electrical contact to individual molecules.