The effect of different concentrations of chloride on the structure of CuUPD on Pt(111)

The influence of the concentration of chloride ions on the underpotential d eposition of copper onto Pt(111) has been studied by AES, LEED and RHEED. T he results demonstrate that the arrangements of the superlattices of (2 x r oot 3), '(4 x 4)', c(11 x root 3) and ((8)(1)(1)(2)), real space structures of the corresponding LEED/RHEED patterns are), and their packing density o n the copper covered Pt(111) are clearly determined by the Cl- concentratio n. derived from a comparison of the LEED spot intensities with those obtain ed by kinematic calculations. Thus the superstructures are interpreted as o rdered Cl adlayers on top of a pseudomorphic-grown Cu UPD layer. A compress ed copper UPD adlayer with a Cu-Cu distance of 0.259 nm determined by EXAFS could not be observed by RHEED. (C) 1999 Elsevier Science Ltd. All rights reserved.