He reflectivity study of a self-assembled monolayer of decanethiol on Au(111)

We present a study of a self-assembled monolayers of decanethiol on Au(111) performed by means of low energy He beam scattering. Full monolayers of standing up molecules have been grown at 275 K in ultra high vacuum and the measurements have been performed between 40 and 60 K. In particular, specular reffectivity has been measured before and after an annealing to 360 K and features associated to resonances with bound states of He atom interacting with the CH3 groups of the standing-up organic molecules have been observed. Through the analysis of the angular position of these features four bound state levels have been determined. The comparison between the levels of the as-deposited monolayer and those of the annealed one shows that the two spectra are very similar and only differ slightly on the value of the deepest level. (C) 2004 Elsevier B.V. All rights reserved.