Identification of vibrational signatures from short chains of interlinked molecule–nanoparticle junctions obtained by inelastic electron tunnelling spectroscopy

Abstract

Short chains containing a series of metal–molecule–nanoparticle nanojunctions are a nano-material system with the potential to give electrical signatures close to those from single molecule experiments while enabling us to build portable devices on a chip. Inelastic electron tunnelling spectroscopy (IETS) measurements provide one of the most characteristic electrical signals of single and few molecules. In interlinked molecule–nanoparticle (NP) chains containing typically 5–7 molecules in a chain, the spectrum is expected to be a superposition of the vibrational signatures of individual molecules. We have established a stable and reproducible molecule–AuNP multi-junction by placing a few 1,8-octanedithiol (ODT) molecules onto a versatile and portable nanoparticle–nanoelectrode platform and measured for the first time vibrational molecular signatures at complex and coupled few-molecule–NP junctions. From quantum transport calculations, we model the IETS spectra and identify vibrational modes as well as the number of molecules contributing to the electron transport in the measured spectra.