Film growth and X-ray induced chemical reactions of thiophene adsorbed on Au(1 1 1)

The adsorption behavior of thiophene on Au(1 1 1) surface has been extensively studied as a function of coverage by two inner-shell spectroscopies; X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Thiophene was adsorbed on Au(1 1 1) at about 130 K with several exposures. It was revealed that the growth of thiophene film on Au surface has three processes: (1) growth of a flat-lying monolayer; (2) growth of a “compressed(inclined)” monolayer; (3) growth of a standing multilayer. Photochemical reactions induced by X-ray irradiation on the thiophene film have also been studied. The yield of the reaction products drastically increases above the coverage at which the compressed monolayer is formed. XPS and NEXAFS results suggest that the photochemical products are oligothiophenes and thiolates. X-ray energy dependence on the yield shows that the yield is significantly enhanced above the C K-edge, which means that the core hole creation of the carbon atom plays an important role for these reactions.