The mechanism of localized electrodeposition on the nanometer scale is stud
ied using the tip of an electrochemical scanning tunneling microscope as a
"nanoelectrode," which is retracted from the substrate (working electrode)
during growth of the clusters. The system chosen exemplarily is Au(111)/Co2
+, which shows a relatively weak substrate/deposit interaction compared to
the strong interaction characteristic of underpotential deposition systems.
The width and height of the clusters, which can be grown with diameters ev
en below 10 nm, are determined by the diameter of the tip apex, the distanc
e between tip and substrate, the substrate potential, and by the amount of
Co transferred to the substrate via the tip. The influence of these paramet
ers on the cluster growth can be well understood assuming diffusion as the
mechanism of Co transfer from the rip to the substrate. Field and charging
effects of either tip or substrate can be excluded due to the large distanc
e of approximately 20 nm between both electrodes. (C) 2001 The Electrochemi
cal Society. All rights reserved.