Cu-Ni thin films electrodeposited on Si: Composition and current efficiency

Constantan/Cu bilayers were electrodeposited potentiostatically at room tem perature from a citrate electrolyte containing both copper and nickel sulfa tes. RBS and EDS techniques were used to determine bath efficiency, growth rate and layer composition as a function of deposition voltage. It is shown that the layer composition can be controlled by the applied potential (rel ative to a saturated calomel electrode (SCE)), being very sensitive to it, and may range from pure copper (at -0.45 V/SCE) up to a solid solution of 2 0 wt% Cu in Ni (at -1.2 V/SCE). Current efficiencies were also dependent on the applied potential, decreasing continuously from around 80% at -0.45 V/ SCE, down to less than 10% for potentials more negative than -1.45 V/SCE. F or the compositions of interest, however, i.e. 45-50 wt% Ni, current effici encies were around 70%. Growth rates of 1.8 and 3.7 Angstrom /s. for copper and constantan, respectively, were obtained.