Morphology and magnetic properties of Co thin films electrodeposited on Si

The electrodeposition of thin films of the element cobalt on silicon wafers opens the possibility of producing magnetic structures on top of a technological substrate using an efficient and inexpensive method. In this paper, we present an extensive study of the electrodeposition of Co on Si(100) n-type substrates. Co thin films with metallic appearance and uniform thickness were obtained at deposition rates of 0.6 (2.8) nm/s for the 26 (104) mM Co electrolyte. A strong dependence of the surface roughness on the nucleation mechanism, i.e., instantaneous or progressive, was observed for layer thicknesses below 300 nm. Simultaneous magneto-optical Kerr effect and magnetoresistance measurements showed that magnetic behavior depends on the nucleation mechanism as well. Coercivity decays with increasing thickness, t, following a power law of the type t(-n), with n = 1.6 (2.1) for the 26 (104) mM electrolyte, which reflects a strong dependence of the magnetic behavior on surface effects. A large variation of the in-plane coercive fields was observed for the 104 mM electrolyte, which varied from 730 to 13 Oe as film thickness increased from 26 to 260 nm. (C) 2002 The Electrochemical Society.