Electrochemical Atomic Layer Deposition of CdS on Ag Single Crystals: Effects of Substrate Orientation on Film Structure

Electrochemical atomic layer epitaxy (ECALE), also known as electrochemical atomic layer deposition, is a method based on under potential deposition, which allows the layer by layer growth of compounds on single crystal substrates. This paper reports on the electrochemical and structural investigation carried out on CdS thin films grown by ECALE on Ag(110) and Ag(100). Electrochemical experiments demonstrate that the CdS thin films, grown by ECALE, are highly ordered and epitaxial. The stoichiometric composition of the thin films was calculated using the charges associated with the anodic and cathodic stripping of CdS. The results indicate a 1:1 ratio between the elements. Characterization of the samples, performed by surface X-ray diffraction and X-ray reflectivity, suggests the presence of a crystalline CdS thin films epitaxial with the substrates. Moreover, a strong influence of the substrate orientation on the film structure is observed: CdS in wurtzite structure was found on Ag(100), while on Ag(110) the two CdS crystalline forms (wurtzite and zincblende) were present.