Role of substrate in the surface diffusion and kinetic roughening of nanocrystallised nickel electrodeposits

Abstract

The surface growth and roughening of nano-crystallised Ni electrodeposits prepared at the same conditions have been studied on Cu, Au and ITO substrates. The Ni films obtained are characterised by the same face-centred cubic structure with a texture affected by the substrate chemical nature. Practically, the same small-sized grains of 83 nm mean height depicting a statistical mono-mode feature grow on Cu. A three-modal feature corresponding to the biggest and compact crystallites of 335, 368 and 400 nm mean height is obtained with Au. Two typical modes, respectively, linked to isolated big crystallites of 343 nm mean height and large zones of small grains of 170 nm height, result from the ITO effect. The surface transport properties of Ni ad-atoms on each substrate have been studied from the theoretical approach including the film global roughness measured by AFM. It is shown that the ad-atom diffusion coefficients ( D s ) ranged in the interval 10 −10–10 −9 cm 2 s −1 are greatly affected by the non-equilibrium conditions of the film formation. Cu and ITO, respectively, lead to Λ s =11.92 and 14.30 nm, while the higher D s value and diffusion length Λ s =37.32 nm are obtained with Au substrate.