AN XPS STUDY OF HETEROCYCLIC THIOL SELF-ASSEMBLY ON AU(111)

The adsorption of the heterocyclic thiol 2-mercaptobenzimidazole (2MBI ) self-assembled on Au(lll) from the liquid phase has been studied usi ng high resolution X-ray photoelectron spectroscopy (XPS). On the basi s of chemical shifts of the nitrogen (1s) and sulphur (2p) electron bi nding energies for liquid assembled layers, it is concluded that the m olecule bonds to Au in the thiol form. A secondary co-ordination with the surface via the unprotonated nitrogen heteroatom is also possible. Angular dependence of core level intensities and a packing density/la yer thickness estimation is consistent with a single monolayer of 2MBI adopting a 'flat-lying' orientation, although slight inclination of t he plane of the molecule cannot be ruled out. Liquid phase self-assemb ly resulted in films which also contained oxygen and excess carbon. Di rect in situ sublimation of 2MBI onto Au(lll) yielded oxygen-free laye rs, however, partial decomposition of the molecule occurs resulting in the formation of atomic sulphur. In the case of ex situ sublimed film s, atomic and higher oxidation state sulphur are observed. (C) 1998 El sevier Science B.V. All rights reserved.