Surface And Interfacial Alloys Of Palladium With Copper(100): Structure, Chemistry, And Kinematics

The interaction between Pd and the Cu(100) surface has been studied by surface science techniques. When Pd is evaporated onto Cu(100) at 110 K, small Pd islands form on the surface. At substrate temperatures above approximately 180 K, mixed Pd-Cu interfacial layers form. For Pd deposition at 300 K, c(2x2) and p4g surface alloy structures form near 0.5 and 1.0 monolayer (ML) Pd coverage respectively. Above one ML, disordered Pd overlayers form. The surface alloy structures are metastable only, since heating irreversibly segregates Cu to the surface.;The chemistry of the Pd and Cu atoms in the interfacial layers is changed with respect to the pure metals. Changes in their CO chemisorption properties correlate with shifts in the valence band and core level spectra. The core level binding energy shifts are consistent with charge transfer from Pd to Cu. The valence band spectra show a Pd derived feature 1.6 eV below the Fermi level characteristic of Pd in a Cu matrix.;The kinetics of formation of the c(2x2) surface alloy from adsorbed Pd has been studied. The domain growth is self-similar, and the development of order is well described by an exponential growth law. The measured growth exponent and activation energy for ordering are 1/8 and {dollar}\approx{dollar}0.9 eV respectively. The activation barrier to concerted Pd-Cu place exchange is {dollar}\approx{dollar}0.34 eV