Comparative in situ STM studies on the electrodeposition of ultrathin nickel films on Ag(111) and Au(111) electrodes

Results of an in situ scanning-tunneling microscopy (STM) study on the init ial stages of Ni electrodeposition on Ag(111) are presented and compared wi th previous results on Au(111). In the submonolayer range the STM results i ndicate substantial place exchange of Ni with Ag surface atoms. Submonolaye r Ni islands are formed almost exclusively at the step edges, they are part ly embedded into the upper terrace. in contrast, on Au(111) place exchange of Ni adatoms with the Au substrate occurs exclusively at the elbow sites o f the herringbone reconstruction, and adlayer nickel islands nucleate selec tively on top of the embedded Ni atoms (low overpotential) or also at steps (high overpotential). At multilayer coverages atomically smooth Ni deposit s are found on both metal substrates with a lattice constant similar to tha t in metallic Ni, On Ag(111) large, quasi-two-dimensional Ni islands are ob served, contrasting the almost perfect layer-by-layer growth on Ni/Au(111). The density of structural defects within the Ni islands on Ag(111) is sign ificantly lower than for the Ni film on Au(111). (C) 1999 The Electrochemic al Society. S0013-4651(98)09-060-0. All rights reserved.