Étude par la diffraction des électrons lents et la spectroscopie auger de l'adsorption du soufre sur le platine

The adsorption of sulphur on the (111), (100) and (110) faces of platinum has been studied by LEED and Auger spectroscopy. By the combined use of radioactive S³⁵ the contents of the surface unit meshes were determined “in situ” for each state of adsorption. On the (111) face one observes a preliminary adsorption with localization of sulphur atoms at sites of maximum coordination of the metal. At higher pressures and temperatures, S-S distance contracts and a compact hexagonal arrangement, with sulphur atoms outside sites, is obtained. The thermal stability of the various structures was studied as a function of sulphur coverage. During adsorption on the (100) and (110) faces, two steps may be distinguished: the first one seems to correspond to an adsorption in sites, the second corresponds to the formation of a two-dimensional compound whose square mesh is slightly different on the two faces.