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 electrochemical deposition of thin Cd films. We also investigate the growth-kinetics and the electronic features of these films by using optical second harmonic generation. The electrochemical and optical data are combined in the framework of a phenomenological theory. Numerical calculations are used to compare this theory with experiment. The films grown with submonolayer coverages of Cd are analyzed in detail. The results indicate that in the initial stage, the deposited Cd adatoms are partially charged. As the saturation coverage is reached, these adatoms lose most of their charges by mutual depolarization, form small clusters, and finally aggregate into larger structures. The optical data also imply that the surface free electron density of Mo changes due to electrodeposition, and the Cd-film responds to a resonance transition near the second harmonic frequency (2.34 eV) of our experiment.