Growth and Alloying of Ultra-Thin Zn Layers on Pd(110)

Abstract

Growth, alloying, and structure of ultra-thin layers of Zn deposited onto Pd(110) were investigated by low-energy ion scattering, low-energy electron diffraction, Auger electron spectroscopy, and temperature-programmed desorption. In the initial deposition stage at room temperature, intermixing between Zn and Pd occurs, leading to an alloyed interface layer, which, with increasing deposition time, is then overgrown by Zn adlayers with a rough surface morphology. At 3 ML, a transition takes place from pseudomorphic growth to bulk-like hcp Zn(001) films. Upon annealing of the as-deposited films to temperatures above 450 K, Zn surface atoms start to migrate into subsurface layers, leading to the formation of a PdZn surface alloy with local 1:1 stoichiometry. The precise onset temperature for this process depends on the initial Zn coverage. The resulting 1:1 surface alloy has a strong monolayer character, is pseudomorphic, and exhibits a small Pd-up/Zn-down buckling and a (2 × 1)periodicity with Pd and Zn atoms located alternatingly along the close-packed atomic rows. This structure can be regarded as descending from the (101) surface of the tetragonal bulk PdZn intermetallic phase.