Study of the initial stages of copper deposition by in situ scanning tunnelling microscopy

Abstract

The initial stages of copper deposition on gold single-crystal electrodes, comprising the formation of a Cu monolayer at underpotentials as well as nucleation and growth of small Cu clusters at overpotentials, has been studied in various electrolytes by in situ scanning tunnelling microscopy (STM). Individual atoms of the bare gold surface and of the Cu adlayer in the underpotential deposition (UPD) range could be clearly resolved. The nucleation-and-growth behaviour of Cu in the absence and presence of crystal violet has been investigated. In both cases nucleation starts preferentially at surface imperfections such as step edges with a high density of kinks, but the organic additive has a marked influence on the growth behaviour, favouring a quasi-two-dimensional spreading across the surface. The development of the shape of a Cu cluster with time during the deposition process has also been monitored. Finally, possible influences of the tip on the growth behaviour are discussed.