Identifying Highly Conducting Au鈥揅 Links through Inelastic Electron Tunneling Spectroscopy

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• 作者：Giuseppe Foti ; H茅ctor V谩zquez ; Daniel S谩nchez-Portal ; Andr茅s Arnau ; Thomas Frederiksen
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：November 20, 2014
• 年：2014
• 卷：118
• 期：46
• 页码：27106-27112
• 全文大小：480K
• ISSN：1932-7455

文摘

We use inelastic electron tunneling spectroscopy first-principles simulations to identify the different chemical bonds present at metal鈥搈olecule junctions. We unambiguously identify the nature of these bonds from two distinctive features in the calculated spectra: (i) the presence (or absence) of active vibrational modes and (ii) the dependence of vibrational frequencies on electrode separation. We use this method to present a study of the vibrational properties of alkanes bound to the electrodes via highly conducting Au鈥揅 links. In the experiment, these links were formed from molecules synthesized with trimethyl-tin (SnMe<sub>3sub>) terminations, where the SnMe<sub>3sub> groups were removed in situ at the junction, in a process involving both breaking and formation of bonds [Cheng, Z.-L.; Skouta, R.; V谩zquez, H.; Widawsky, J. R.; Schneebeli, S.; Chen, W.; Hybertsen, M. S.; Breslow, R.; Venkataraman, L. Nat. Nanotechnol. 2011, 6, 353鈥?57]. We obtain the vibrational fingerprint of these direct Au鈥揳lkane links and extend this study to the other scenario considered in that paper (bonding via SnMe<sub>2sub> groups), which may be relevant under other experimental conditions. We also explore the effect of deuteration on inelastic electron tunneling spectroscopy (IETS). Complete deuteration of the molecules diminishes the differences of the spectra corresponding to the two bonding geometries, making identification more difficult. IETS of an isolated SnMe<sub>3sub> fragment provides an additional basis for comparison in the characterization of the molecular junction.