Photoelectron spectroscopy study of irradiation damage and metal-sulfur bonds of thiol on silver and copper surfaces

Self-assembled 1-dodecanethiol monolayers (SAMs) on silver and copper surfaces have been characterized with X-ray photoelectron spectroscopy (XPS) using both the synchrotron radiation and conventional Mg Kα excitation. Irradiation-induced changes in thiolate SAMs on Cu and Ag were observed. The identification of the sulfur species has been done. Results obtained confirm earlier studies of n-alkanethiols on silver. On copper (C12S/Cu), the observed S 2p spectrum is quite broad but the use of different excitation energies enabled us to identify four sulfur species on the surface. A S 2p3/2 component of copper thiolate is observed at 162.6 eV. Three more doublets (161.9 eV, 163.2 eV and 163.8 eV) have been observed to develop during irradiation and they are assigned to chemisorbed sulfur on copper, to different dialkylsulfides and to sulfur-sulfur bonding.