Co–W films prepared from electroplating baths with different complexing agents

Abstract

The influence of different complexing agents with hydroxycarboxylic acid group on the electrodeposited Co–W thin films has been investigated. Comparison between the polarisation curves shows that the negative shift on the electrodeposition potential increased in the following order: no complexing agent, tartrate, malate, gluconate and citrate. The particular shapes of the j–t transients indicate that a nucleation and growth process was involved for the Co–W electrodeposition in the presence of complexing agents investigated. The reduced current transients follow the instantaneous nucleation model for all four complexing agents at the initial stages. Surface morphology, phase composition and magnetic properties were observed by means of field emission SEM, X-ray diffraction and vibrating sample magnetometer respectively. It has been found out that surface morphology and phase composition were markedly affected by the nature of the complexing agents. In the absence of complexing agents and in the presence of citrate, reflections of Co₇W₆, Co (1 0 0) and Co (0 0 2) appeared simultaneously. For the deposits obtained from solutions containing malate, there are two main peaks: Co₇W₆ and Co (0 0 2). In the case of tartrate, two peaks of Co are observed: Co (0 0 2) and Co (1 0 0). Reflections of Co (0 0 2) appeared for the deposits prepared from gluconate baths. Co–W magnetic thin films presented good soft magnetic properties (H_c = 2 Oe, M_s = 1403 emu cm⁻³) compared with pure cobalt thin films (1370 emu cm⁻³) when 0··3 mol L⁻¹ citrate was used as complexing agent.