NUCLEATION AND STRUCTURAL PROPERTIES OF NICKEL FILMS ELECTRODEPOSITED FROM CHLORIDE AND SULFATE BATHS

Nickel films electrodeposited from chloride and sulfate baths at pH 3.8 have been investigated. The influence of the plating baths on the electrochemical growth and the characteristics of nickel were studied by means of cyclic voltammetry, potentiostatic steps (chronoamperometry), atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The electrocrystallization mechanism was analyzed using the Scharifker and Hills model. The nucleation mechanism was found to be progressive at -1.1V versus SCE, while at elevated overpotentials (more negative than -1.2V versus SCE) instantaneous nucleation behavior was obtained. AFM characterization of the deposits indicated that the baths composition influences greatly the morphology of the deposits. XRD analysis indicated polycrystalline growth of the Ni film with a preferred (111) orientation with the fcc structure for both baths. The Ni crystallite sizes are 19-31nm for the sulfate bath and 14-33 nm for the chloride one.