Surface roughness and morphology of Co-(Fe and Ni) binary alloy electrodeposits studied by atomic force microscopy

Abstract

The insertion of cobalt species in 2 µm thick nickel and iron matrixes is performed by electrodeposition. The influence of the bath or sample composition and the growth velocity on the morphology and the interface pattern of the resulting alloys are studied following the behaviour of the root-mean-square surface roughness . It is shown here that pure Ni and Fe electrodeposits exhibit high values. Low Co concentrations in each of the matrices prompts a sensitive decrease of this parameter until a typical min value is reached. This value is affected by the growth velocity v and the chemical nature of the alloy. also appears to be connected to the textural pattern of the sample surface. The increase of v in the deposition of pure Ni and Fe destroys the preferred growth orientation of these materials, which is accompanied by an increasing movement of . The presence of Co2+ species in the deposition bath reveals that the = f(v) curves of the resulting CoxNi(1-x) and CoxFe1-x samples always exhibit a critical point (´´min,vmin) corresponding to a change in the preferred growth orientation of the alloy system, without structural modification. The scaling analysis of the pure metal and alloy surfaces obtained at v = 5.47 µm s-1 always present a self-affine fractal pattern. Ni and Fe lead to one roughness exponent while the insertion of Co in each of the two matrices engenders two roughness exponents. The main exponent values obtained with the Co, Fe and Co-Fe samples are consistent with the local non-conservative Kardar-Parisi-Zhang dynamics while those of Ni and Co-Ni interface growths are in agreement with the local conservative model.