A SEXAFS INVESTIGATION OF SELF-ASSEMBLED MONOLAYERS ON SILVER

Sulfur K-edge surface extended X-ray absorption fine structure (SEXAFS ) measurements have been carried out on self-assembled monolayers (SAM s) of alkylthiols adsorbed onto evaporated silver surfaces. By using t he Auger yield method, it was found that adequate data could be obtain ed to allow a preliminary determination of the adsorption site of the S head groups on the predominantly (111) Ag surface. For SAMs of butan ethiol and octanethiol, the three-fold hollow site was identified as t he most probable position for the S atom. In addition to studies of as -prepared monolayers, the evolution of the NEXAFS spectra of octanethi ol SAMs on silver which were progressively photo-oxidised was also inv estigated. The results supported the model derived for this process fr om other techniques. (C) 1998 Elsevier Science B.V.