Self-assembly of an aromatic thiolate on Cu(100): The local adsorption site

The long-range ordered p(2 x 2) self-assembled monolayer formed by dosing 2-mercaptobenzoxazole (MBO, C7H5NOS) on the Cu(100) surface at room temperature has been structurally characterised by means of normal incidence X-ray standing wavefield absorption (NIXSW) at both (200) and (111) reflections. The results show that the S atom, through which the adsorbed molecular thiolate species bonds to the surface, has an interlayer spacing of 1.33 +/- 0.05 A relative to the extended bulk scatterer planes (200) parallel to the surface and occupies the four-fold coordinated hollow site, with no evidence of major reconstruction. These results are entirely consistent with previous findings for a number of thiolates formed on (100) noble metal surfaces. The role of the head-group to surface potential corrugation and intermolecular interactions in determining the adsorption site and ordering of this aromatic molecular adsorbate is discussed. (c) 2005 Elsevier B.V. All rights reserved.