Molecular orientation of 2-mercaptobenzoxazole adsorbed on Cu(1 0 0) surface

The long range ordered p(2 × 2) self-assembled monolayer formed by dosing 2-mercaptobenzoxazole (MBO, C7H5NOS) on the Cu(1 0 0) surface at room temperature has been investigated by means of near edge X-ray adsorption fine structure (NEXAFS) technique at the sulphur K-edge. NEXAFS S–K-edge spectra have been recorded at different incident photon angles with respect to the Cu(1 0 0) surface, using linearly polarised synchrotron radiation. A clear spectral feature has been observed close to the absorption edge, with higher intensity at grazing incidence, assigned to the σ*(S–C) resonance, corresponding to the transition from the S 1s core level to the σ*(S–C) antibonding molecular state. The angular dependence of the σ*(S–C) resonance intensity clearly indicates that the S–C axis is nearly perpendicular to the surface (13° ± 13°), confirming the major role of S in bonding to the surface, and the influence of the π–π interaction between the molecules in driving the almost upright position at saturation coverage.