Eletrodeposição de filmes finos de cobalto sobre ouro

Abstract

The preparation of thin and ultrathin cobalt films has received increasing attention due to their important magnetic properties, such as perpendicular magnetic anisotropy, and relevant applications such as data storage, magnetic sensors and spintronics. Electrodeposition has proven to be an important and alternative technique to physical methods for producing thin films, as it allows the material to be deposited on non-planar surfaces at a low cost, when compared to deposition techniques that use vacuum. The main objective of this work is to study the electrodeposition of thin and ultrathin cobalt films on three different gold substrates (CDtrode (gold electrode using recordable compact discs (CD) as a gold source), gold/mica and gold/silicon), evaluating their effects on the properties of the deposited films. The substrates were characterized by electrochemical methods, X-ray diffraction (XRD) and atomic force microscopy (AFM). The potentiostatic technique was adopted with three electrodes and a base solution with cobalt sulfate. From the analysis of cyclic voltammograms it was possible to identify the oxidation and reduction potentials, allowing the determination of deposition rates for different potentials. Current transients made it possible to observe nucleation peaks and other regimes during film deposition. Results obtained by X-ray diffraction showed that the three substrates presented crystallographic orientation (111). Images of the surfaces, obtained by AFM, demonstrated that they all have roughness on the order of nanometers and uniform surface coverage, thus being suitable substrates for the deposition of magnetic films. The linear dependence of the peak currents as a function of the square root of the scanning speed defined that the process is quasi-reversible controlled by diffusion. The cobalt oxidation process on the surface of all substrates is controlled by diffusion, as shown in the graph of the log of the anode peak current versus the log of the potential sweep speed.