Sulfur Interaction with Cu(100) and Cu(111) Surfaces: A Photoemission Study

Abstract

Results of a high-resolution synchrotron photoemission study of sulfur adsorption on Cu(100) and Cu(111) surfaces are reported. Sulfur adsorption was performed by immersion of pristine samples into aqueous Na2S, which provokes strong sulfidation of copper. Annealing leads to partial elimination of S and progressive formation of well-ordered surface sulfur phases followed here by LEED. This translates into sizable Cu 2p core level binding energy (CLBE) shifts as well as changes in the S 2p binding energies. For Cu(111) we see evolution at the higher temperature to the (√7 × √7)R19.1° phase as identified by LEED, with a S 2p3/2 binding energy of 161.45 eV. An intermediate phase with an S 2p3/2, binding energy of 161.15 eV appears at lower temperatures. For Cu(100) at 300 °C we see the appearance of the known 0.47 ML S coverage (√17 × √17)R14° structure, with S 2p3/2 CLBE of 161.15, 161.62, and 162.10 eV. At higher temperatures some S atom loss occurs, and we observe a p(2 × 2)-S phase, with S 2p3/2 CLBE of 161.05 eV and a smaller component at 164.45 eV that could correspond to local c(4 × 2) domain boundaries as identified in earlier studies. The core level binding energies of Cu 2p are reported along with valence band characteristics.