Etude des mécanismes de l’électrodéposition des alliages Co-Cu sur un substrat semi-conducteur

Abstract

In this work, we are interested in studying the electrochemical characteristics, morphological, structural and magnetic properties of Co-Cu granular system obtained by electrodeposition on an n-Si wafer from a sulfate bath. Also, the optimization of the conditions and the kinetic study of the electrodeposition of Co-Cu layers are investigated. The nucleation and growth kinetics at the initial stages of Co-Cu studied by current transients indicate a 3D island growth (Volmer–Weber); it is characterized by an instantaneous nucleation mechanism followed by diffusion limited growth. The analysis of composition reveals a variation of the deposit composition when switching potential is varied. The morphological, structural and magnetic characterizations of the obtained Co-Cu were carried out using scanning electron microscopy (SEM), X-ray diffraction (XRD), and alternating gradient field magnetometers (AGFM).The surface morphology of the deposits varies greatly with the potential deposited. X-ray diffraction analysis showed that the films crystallize in varieties of phases; a mixture of Co fcc and hc, and Cu fcc structures, greatly related to applied potential. The increase of the applied potential induces a decrease in the grain size and the lattice constant. The magnetization of the alloys was found to be enhanced for high Co concentrations and consequently at high deposition potential. This study allowed us to qualitatively determine the conditions for electrodeposition of Co-Cu and in particular the effect of applied potential. This is fundamental and indispensable for the realization of a magnetic device electrochemically.