Comment On 'resolving The Depth Coordinate In Photoelectron Spectroscopy -comparison Of Excitation Energy Variation Vs. Angular-resolved Xps For The Analysis Of A Self-assembled Monolayer Model System' By S.v. Merzlikin Et Al. [surf. Sci. 602 (2008) 755]

摘要

In a recent paper published in this journal, Merzlikin et al. compared two methods, angular-resolved X-ray induced photo-electron spectroscopy (ARXPS) and excitation energy variation in photoelectron spectroscopy (ERXPS), to obtain concentration depth-profiles of elements in the near-surface region of model samples - self-assembled monolayers of n-octadecanethiol ("C_(18)-SAM") adsorbed on gold substrates of different surface roughness. Both methods take advantage of varying sampling depth in photoelectron spectroscopy with emission angle or excitation energy. Importantly, C_(18)-SAM is the recommended model overlayer material with known structure, composition and thickness. The surface corrugation of gold substrates is characterized by the root mean square (rms) values of the height derived from atomic force microscopy (AFM) surface mapping. However, as discussed below, this parameter is not decisive in photoelectron spectroscopy.