E´tude par la diffraction dese´lectrons lents et la spectroscopie auger de l'adsorption du soufre sur l'or

A study has been made of the adsorption of sulphur on the (111), (100) and (110) faces of gold using LEED and AUGER spectroscopy combined with a radioactive tracer technique employing ³⁵S. The content of the surface unit mesh can thus be determined. A preliminary adsorption state with localization of sulphur atoms at sites of maximum coordination of the metal is observed. This state is transformed by reconstruction into a surface compound, or adsorbed two-dimensional sulphide. The results are compared with previous results from HEED and experiments of reversible chemisorption. On the (110) face the equilibrium between different adsorbed phases of sulphur is studied under conditions for which sulphur dissolution or evaporation is negligible. A temperature- coverage diagram is determined which shows the regions where sulphur is present at equilibrium in one or two phases.