Initial stage of Pb adsorption on Ni(111) studied by LEED and ICISS

Abstract

Impact-collision ion scattering spectroscopy (ICISS) and low energy electron diffraction (LEED) have been used to determine the surface structure in the initial stage of Pb adsorption on Ni(111). Three kinds of surface structure were observed in the Pb coverage dependence of LEED patterns; 1 × 1(0 < θ < 0.25), 3 × 3(0.25 < θ < 0.45) and (4 × 4)′ (0.54 < θ < 1.0). The coverage of 0.54 ML at the completion of the surface phase change to a (4 × 4)′ structure was in agreement with that observed by RBS measurements and corresponds to a complete one atomic layer thick coverage of Pb atoms. At a coverage of 0.45 < θ < 0.54, the lead-lead distance changed drastically from 3.74 Å to 3.39 Å. In the (4 × 4)′ structure, the lead-lead distance of 3.39 Å is 6% larger than that of 3.2 Å for an ideal 4 × 4 structure. Pb islands grow as a single overlayer structure like a one layer thick floating solid on the Ni(111) surface.