UHV-EC Characterization of Ultrathin Films Electrodeposited on Well-Defined Noble Metals. I: Pd on Pt(111)

摘要

A combination of conventional electrochemistry (cyclic voltammetry and coulometry) and ultrahigh vacuum electron spectroscopies (Auger electron spectroscopy and low-energy electron diffraction) was used to characterize the interfacial chemistry of ultrathin Pd films in the presence of adsorbed and aqueous bromide. Potential-controlled adsorption-desorption cycles of aqueous bromide exerted surface smoothening effects on ultrathin Pd films with defect sites (steps); this procedure, dubbed as electrochemical (EC) annealing, constituted a nonthermal analog to conventional annealing. EC-annealed ultrathin Pd films exhibited long-range surface order and remained free of oxygen adspecies. Pd adatoms occupying step sites were selectively dissolved and/or rearranged to assume equilibrium positions in a well-ordered (1 × 1) film.