Inelastic Tunneling Spectroscopy of Gold-Thiol and Gold-Thiolate Interfaces in Molecular Junctions: The Role of Hydrogen

Abstract

It is widely believed that when a molecule with thiol (S-H) end groups bridges a pair of gold electrodes, the S atoms bond to the gold and the thiol H atoms detach from the molecule. However, little is known regarding the details of this process, its time scale, and whether molecules with and without thiol hydrogen atoms can coexist in molecular junctions. Here we explore theoretically how inelastic tunneling spectroscopy (IETS) can shed light on these issues. We present calculations of the geometries, low bias conductances and IETS of propanedithiol and propanedithiolate molecular junctions with gold electrodes. We show that IETS can distinguish between junctions with molecules having no, one or two thiol hydrogen atoms. We find that in most cases the single-molecule junctions in the IETS experiment of Hihath et al. [Nano Lett. 8, 1673 (2008)] had no thiol H atoms, but that a molecule with a single thiol H atom may have bridged their junction occasionally. We also consider the evolution of the IETS spectrum as a gold STM tip approaches the intact S-H group at the end of a molecule bound at its other end to a second electrode. We predict the frequency of a vibrational mode of the thiol H atom to increase by a factor \sim 2 as the gap between the tip and molecule narrows. Therefore, IETS should be able to track the approach of the tip towards the thiol group of the molecule and detect the detachment of the thiol H atom from the molecule when it occurs.

11 pages, 7 figures, 1 table

References in corpus (20)

• Molecular Transport Junctions: Vibrational Effects
• Inelastic transport theory from first-principles: methodology and applications for nanoscale devices
• Inelastic electron tunneling via molecular vibrations in single-molecule transistors
• Highly conductive molecular junctions based on direct binding of benzene to platinum electrodes
• Tuning the Kondo effect with a mechanically controllable break junction
• Unified description of inelastic propensity rules for electron transport through nanoscale junctions
• Inelastic effects in molecular junctions in the Coulomb and Kondo regimes: Nonequilibrium equation-of-motion approach
• Resonant vibrations, peak broadening and noise in single molecule contacts: beyond the resonant tunnelling picture
• Origin of Discrepancies in Inelastic Electron Tunneling Spectra of Molecular Junctions
• Non-linear response of molecular junctions: The polaron model revisited
• Vibrational absorption sidebands in the Coulomb blockade regime of single-molecule transistors
• Vibronic effects on resonant electron conduction through single molecule junctions
• Single-Molecule Device Prototypes for Protein-Based Nanoelectronics: Negative Differential Resistance and Current Rectification in Oligopeptides
• Phonon Driven Nonlinear Electrical Behavior in Molecular Devices
• Non-Local Conductance Modulation by Molecules: STM of Substituted Styrene Heterostructures on H-Terminated Si(100)
• Identification of the Molecule-Metal Bonding Geometries of Molecular Nanowires
• Tight Binding Model of Mn12 Single Molecule Magnets: Electronic and Magnetic Structure and Transport Properties
• Ligand-based transport resonances of single-molecule magnet spin filters: Suppression of the Coulomb blockade and determination of the orientation of the magnetic easy axis
• Identification of the Atomic Scale Structures of the Gold-Thiol Interfaces of Molecular Nanowires by Inelastic Tunneling Spectroscopy
• Vibrational features in inelastic electron tunneling spectra

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