He reflectivity study of a self-assembled monolayerof decanethiol on Au(1 1 1)

We present a study of a self-assembled monolayers of decanethiol on Au(1 1 1) 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 reflectivity 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.