Atom-by-atom growth of cadmium sulfide thin films by electroreduction of aqueous Cd2+–SCN− complex

Abstract

Electrodeposition of cadmium sulfide thin films was realized by the electroreduction of the aqueous thiocyanato complex of Cd2+. Formation of CdS is supposed to proceed via metal-catalyzed ligand reduction. The film thickness increased linearly with the electricity consumed, confirming the electrochemical growth of CdS. The deposition bath was fairly stable and could be used repeatedly to prepare many CdS films. While all the previously reported techniques for the chemical or electrochemical growth of CdS thin films in aqueous systems are accompanied by homogeneous chemical reactions to generate solid particles of CdS or S in the bulk of the solutions, the present technique seems to be the only example to achieve purely electrochemical growth of CdS from a single solution. The resultant CdS thin film had a uniform structure in which each grain was made up with single phase crystalline hexagonal CdS. When the deposition was carried out on poly-crystalline Ni, the deposited CdS thin film showed a strong preferential orientation with the c-axis perpendicular to the substrate surface, suggesting an epitaxial growth of 6-fold planes of CdS onto Ni(111) planes in a (√3×√3)R30° structure, owing to their small lattice mismatch of 4.17%.