The epitaxial growth of Pd electrodeposition on Au(100) studied by LEED and RHEED

The epitaxial growth of Pd adlayers electrochemically deposited onto Au(100) has been studied by LEED, RHEED and AES. For the first 6 ML, the Pd deposits grow pseudomorphically on Au(100) with a lateral expansion of 4.5% with respect to bulk Pd. The strain in the expanded commensurate (I x 1) Pd layers on Au(100) begins to be relieved at the Pd coverage between 6 and 9 ML range by formation of a compressed Pd film with respect to Au(100) surface and the compression increases continuously with thickness. At ca. 20 ML Pd the lattice constant of the film approaches to the bulk Pd and three-dimensional Pd islands develop since around 30 ML coverage. No superstructure due to the Pd-Au surface alloy can be found for coverages from monolayer up to 30 ML Pd on Au(100). A c(2 x 2) phase has been observed on the Pd-deposited Au(100) electrodes, which is ascribed to ordered Cl adlayers adsorbed on Pd adlayers rather than a Pd-Au surface alloy