The adsorption of silicon on the iridium surface ruling out silicene growth

The adsorption of Si atoms on a metal surface might proceeds through complex surface processes whose rate is differently determined by factors as temperature, Si coverage and metal cohesive energy. Among other transition metals, iridium is a special case since the Ir (111) surface was reported first, in addition to Ag(111), as suitable for the epitaxy of silicene monolayers. In this study we followed the adsorption of Si on the Ir(111) surface by high resolution core level photoelectron spectroscopy starting from the clean metal surface up to a coverage exceeding one monolayer in the temperature range between 300 and 670 K. Density functional theory calculations were carried out to evaluate the stability of the different Si adsorption configurations as a function of the coverage. Results indicate that at low coverage the Si adatoms tend to occupy the hollow Irsites, but a small fraction of them penetrates in the first Ir layer. Si penetration in the Ir surface can take place if the energy gained upon Si adsorption is used to displace the Ir surface atoms rather then being differently dissipated. At Si coverage 1 monolayer the Ir4f spectrum signals that not only the metal surface but also the layers underneath are perturbed. Our results point out that the Si/Ir(111) interface is unstable towards Si-Ir intermixing, in agreement with the silicide phase formation reported in the literature for the reverted interface