Adsorption of alkanethiols and biphenylthiols on Au and Ag substrates: A high-resolution X-ray photoelectron spectroscopy study

Synchrotron-based high-resolution X-ray photoelectron spectroscopy was appl ied to monitor the formation of self-assembled monolayers (SAM) of alkaneth iols (AT) and biphenylthiols on Au and Ag substrates. Pronounced chemical s hifts in the adsorbate- and substrate-related photoemission lines upon SAM formation were observed. Only one sulfur species could be detected in the S 2p spectra of the investigated SAMs, consistent with a thiolate bond. From the fwhm's of the core level photoemission spectra conclusions on the hete rogeneity of the adsorption sites and adsorption geometry can be made. The experimental data imply several (at least two) slightly different adsorptio n geometries for the AT moieties in AT/An. Significant final state effects in the C 1s photoemission were found for both the aliphatic and aromatic SA Ms.