Orientation of Decanethiol Molecules in Self-Assembled Monolayers Determined By Inelastic Electron Tunneling Specstrocopy

We present first-principles calculations for the inelastic electron tunneling spectroscopy (IETS) of decanethiolate molecules sandwiched between Au(111) surface and scanning tunneling microscope (STM) tip, as reported by Hallba ̈ck et al. (Nano Lett. 2004, 4, 2393). It is demonstrated here that the IET spectra are very sensitive to the molecule-metal contact structure, orientation of the molecule adsorbed on the surface, and the distance between the carbon of the terminal methyl group and the STM tip. With correct assignation of the experimental spectral features, the orientation of the molecule and then the probable configuration of the molecular junction are determined.