STRUCTURE-ANALYSIS OF S-ADSORBED ON NI(111) BY LOW-ENERGY LI+ ION-SCATTERING

Low energy ion scattering of Li+ ions with 500 eV energy was applied to analyze the surface structure of S on Ni(111). Polar and azimuthal incident angle dependences were measured for the clean and S covered surface, and the surface geometry was analyzed by the shadowing and blocking features from the single scattering. AES/LEED are used to monitor the surface coverage before and after annealing. The p(2 x 2) and (5 square-root 3 x 2) LEED patterns were observed for S/Ni(111) annealed 6.00 K surface with coverage about 0.25 and 0.40 ML, respectively. The ion scattering data suggested that S atoms were sitting on the fcc hollow site as an overlayer about 0.168 +/- 0.007 nm above the Ni surface for p(2 x 2)S structure. Results for (5 square-root 3 x 2) S/Ni(111) indicate S is present as an overlayer on a reconstructed Ni surface.