Tuning vibrations in single-molecule junctions: inelastic electron tunneling spectroscopy of an alkanedithiol

We study pentanedithiol molecular junctions formed by means of the break-junction technique with a scanning tunneling microscope at low temperatures. Using inelastic electron tunneling spectroscopy and first-principles calculations, the response of the junction to elastic deformation is examined. We show that this procedure makes a detailed characterization of the molecular junction possible. In particular, our results show unequivocally that tunneling takes place through just a single molecule.