| Abstract
| - Self-assembled monolayers (SAMs) of o-xylene-α,α‘-dithiol (o-XDT) on a Au(111) surface have beencharacterized by means of reflection−absorption infrared (RAIR) spectroscopy, ellipsometry, quartz crystalmicrobalance (QCM), and atomic force microscopy (AFM). The RAIR spectral data revealed that o-XDTshould adsorb on gold as a deprotonated form with its benzene ring to assume a perpendicular stance withrespect to the gold substrate. The ellipsometric thickness of the o-XDT SAMs was 8.3 Å, comparable tothe prediction from the RAIR spectra. The QCM data suggested that the self-assembling process could bedescribed in terms of the Langmuir adsorption model, providing the value of the free energy of adsorptionat −28.9 kJ/mol. The limiting surface coverage was determined from the QCM data to be 5.0 × 10-10mol/cm2, corresponding to an area per adsorbate of 33 Å2. The AFM image showed a highly ordered andclose-packed (2 × 2) structure with an area per adsorbate of 29 Å2, which was quite close to the valueobtained from the QCM data.
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