Characterization of electrodeposited thin film of cadmium on molybdenum using optical second harmonic generation

We show in this report that Mo can be used as a supporting substrate for el ectrochemical deposition of thin Cd films. We also investigate the growth-k inetics and the electronic features of these films by using optical second harmonic generation. The electrochemical and optical data are combined in t he framework of a phenomenological theory. Numerical calculations are used to compare this theory with experiment. The films grown with submonolayer c overages of Cd are analyzed in detail. The results indicate that in the ini tial stage, the deposited Cd adatoms are partially charged. As the saturati on coverage is reached, these adatoms lose most of their charges by mutual depolarization, form small clusters, and finally aggregate into larger stru ctures. The optical data also imply that the surface free electron density of Mo changes due to electrodeposition, and the Cd-film responds to a reson ance transition near the second harmonic frequency (2.34 eV) of our experim ent.