Selenium adsorption on Au(111) and Ag(111) surfaces: Adsorbed selenium and selenide films

Results of a high resolution photoemission and electrochemistry study of Se adsorption on Au(111) and Ag(111) surfaces performed by immersion of pristine samples into an aqeuous solution of Na₂Se are presented. Cyclic voltammetry on Au shows formation of selenium adsorbed species and the structures observed in reductive desorption are related to the atomic and polymeric species observed in XPS. In the case of Au(111) XPS spectra in the Se(3d) region indeed show two main features attributed to Se chemisorbed atomically and polymeric Se₈ features. Smaller structures due to other types of Se conformations were also observed. The Au(4f) peak line shape does not show core level shifts indicative of Au selenide formation. In the case of silver, XPS spectra for the Ag(3d) show a broadening of the peak and a deconvolution into Ag_B bulk like and Ag_Se components shows that the Ag_Se is located at a lower binding energy, an effect similar to oxidation and sulfidation of Ag. The Se(3d) XPS spectrum is found to be substantially different from the Au case and dominated by atomic type Se due to the selenide, though a smaller intensity Se structure at an energy similar to the Se₈ structure for Au is also observed. Changes in the valence band region related to Se adsorption are reported.