Biphenylnitrile-Based Self-Assembled Monolayers on Au(111): Spectroscopic Characterization and Resonant Excitation of the Nitrile Tail Group

A series of biphenylnitrile-based self-assembled monolayers (SAMs) on Au(111) was characterized by several complementary spectroscopic techniques, including resonant Auger electron spectroscopy (RAES). In spite of the disturbing role of nitrile, the SAMs exhibited high-quality and expected structural behavior, including the odd−even effects, even though with a lower extent than in the analogous nonsubstituted or methyl-substituted systems. A characteristic feature of the target films, and presumably also a general feature of oligophenyl-based SAMs, is a significant twist of the molecular backbone, similar to the situation in the analogous molecular crystals. No perceptible signal related to tail group-to-substrate transfer of the resonantly excited electron was recorded in the RAES spectra of the target films, even though such a transfer is energetically allowed in some of the cases. This was tentatively explained by the hypothesis that the charge transfer time is too long and lies beyond the range access...