Adsorption of O and Cl on Tl/Si(111) - suppressed spin polarization via bilayer formation

Adsorption of O and Cl on Tl/Si(111) is studied using density functional theory. The surface of the Cl-Tl/Si(111) system was found to be metallic while that for O-Tl/Si(111), semiconducting. It is found, however, that the O/Tl and Cl/Tl interactions in Tl/Si(111) are very similar in nature and lead to the formation of the Tl-O and Tl-Cl bilayers weakly bonded to the Si(111)-1 x 1 substrate. The spin polarization of the Tl-induced gap states, originally present in Tl/Si(111), is also suppressed in both systems.