Fabrication of Thiol-Terminated Surfaces Using Aromatic Self-Assembled Monolayers

Self-assembled monolayers (SAMs) formed from [1,1‘-biphenyl]-4,4‘-dimethanethiol (BPDMT) and [1,1‘;4‘,1‘ ‘-terphenyl]-4,4‘ ‘-dimethanethiol (TPDMT) on Au were characterized by X-ray photoelectron spectroscopy (XPS), high-resolution XPS, infrared reflection absorption spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and water contact angle measurements. The results of all experimental techniques suggest the formation of densely packed and highly oriented SAMs for both BPDMT and TPDMT, with a slightly higher packing density and a smaller molecular inclination in TPDMT/Au. All molecules were found to be bound to the substrate via the thiolate link, i.e., by one of the thiol groups, whereas the second thiol group is located at the SAM−ambient interface. This suggests that aromatic dithiols are well-suited for the fabrication of thiol-terminated SAMs. Such films are of particular importance for molecular electronics, since the thiol group has a high affinity to metals and can be used as a chemical link between a metal nanowire and the molecule.