Molecular conductance spectroscopy of conjugated, phenyl-based molecules on Au(111): the effect of end groups on molecular conduction

• Published in: Superlattices and microstructures 2000-10, Vol.28 (4), p.289-303
• Main Authors: Hong, S, Reifenberger, R, Tian, W, Datta, S, Henderson, J.I, Kubiak, C.P
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems; Electron states and collective excitations in thin films, multilayers, quantum wells, mesoscopic and nanoscale systems; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronics; Exact sciences and technology; Molecular electronic devices; Molecular electronics, nanoelectronics; molecular electronics, thiols, isocyanide, scanning tunneling microscopy; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0749-6036; 1096-3677
• DOI: 10.1006/spmi.2000.0916

Four families of conjugated molecules, containing between one and three phenyl rings and having both thiol (–SH) and isocyanide (–NC) end groups, have been synthesized and assembled as monolayers on flat Au(111) substrates. The conductance spectra G(V) for these molecular wires were systematically measured in UHV conditions using scanning tunneling microscope techniques. The measured conductance spectra for the molecules having thiol end groups are compared to a recent theory for molecular conduction. The favorable comparison indicates that the important properties influencing the conductance of short, conjugated molecular wires having thiol end groups and forming self-assembled monolayers on a Au(111) surface have been successfully identified. The isocyanide molecules reveal a shift in Fermi level of the molecule as a function of phenyl ring number that is opposite to that observed for the thiol-terminated molecules. The trends in molecular conductance determined from this systematic study are summarized and discussed and provide insight into the role played by bonding end groups in electronic conduction.