Electrochemical Atomic Layer Epitaxy deposition of CdS on Ag(111): an electrochemical and STM investigation

The electrochemical atomic layer epitaxy methodology was employed to obtain CdS deposits on Ag(111) by alternate underpotential deposition of up to five layers of sulfur and four layers of cadmium. The charge involved in each layer was determined by cyclic voltammetry. With the exception of the first sulfur layer, the charge involved in the deposition of each sulfur and cadmium layer was the same, indicating the achievement of a stoichiometric, 1:1 ratio, deposit from the second layer. The first layer, which consisted of sulfur on the bare silver surface, involved a higher charge and is to be regarded as an interface between the metal and the compound. The measured charge is in good agreement with that estimated on the basis of STM images. The structure revealed by STM for all but the first layer was a (x7 x7)R19.1°, with one atom per lattice site, relative to the Ag(111) substrate.