Epitaxial growth of a palladium layer on an Au(100) electrode

The electrochemical deposition process of palladium from a PdCl42- complex on an Au(100) substrate was investigated using in situ scanning tunneling m icroscopy (STM). The reactant, i.e. the PdCl42- complex, was found to adsor b on the Au(100) surface with an ordered structure in the potential region where neither a cathodic nor an anodic current flowed. The electrochemical deposition of palladium on the Au(100) proceeded at potentials more negativ e than 1.0 V. The electrodeposition of the first palladium layer started no t only on the terrace but also on gold islands which were formed as a resul t of the lifting process of the reconstructed Au(100) surface and then proc eeded two-dimensionally. The following palladium layer was found to grow ma inly from the deposited palladium region on top of the gold islands. The sh ape of the gold island could be identified even after four palladium layers were deposited. The bulk and surface structures of the deposited palladium layer were characterized by X-ray diffraction (XRD) and the copper underpo tential deposition (upd) reaction, respectively, and the formation of the P d(100) phase with a (1 x 1) surface structure was confirmed. (C) 1999 Elsev ier Science S.A. All rights reserved.