Growth velocity and the topography of Ni-Zn binary alloy electrodeposits

We show that the electrodeposition of Ni-Zn alloys at the lowest growth velocities, upsilon < 0.5 mum/s, exclusively proceeds from an abnormal co-deposition phenomenon. The growth process in this upsilon region greatly depends on the initial [Co2+] concentration of the film deposition bath. A theoretical approach of this process including the role of the saturation surface roughness of the alloy, o(sat), leads to an estimation of the transport properties of the ad-atoms involved during the deposit formation. Their surface diffusion coefficient varying between 1.76 x 10(-10) and 2.40 x 10(-8) cm(-2)/s exhibits a minimal value, D-s = 2.10 x 10(-10) cm(-2)/s located between upsilon = 0.17 and 0.35 mum/s. The spatial scaling analysis of the local roughness., c,, examined according to the power-law sigma = L-alpha reveals that the resulting roughness exponents concurs with the Kardar-Parisi-Zhang dynamics including the restricted surface diffusion. Two main v regions leads to different fractal textural features of the alloy film surface. Below 0.10 mum/s, the roughness exponent obtained is alpha approximate to 0.6, depicting a limited ad-atom mobility. Over upsilon = 0.30 mum/s, this exponent stabilises at alpha approximate to 0.82, indicating an increase of the surface diffusion.