Morphology and Magnetic Properties of Co Thin Films Electrodeposited on Si

Abstract

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 Si͑100͒ n-type substrates. Co thin films with metallic appearance and uniform thickness were obtained at deposition rates of 0.6 ͑2.8͒ nm/s for the 26 ͑104͒ 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 Ϫn , with n ϭ 1.6 ͑2.1͒ for the 26 ͑104͒ 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.The electroplating technique is especially interesting due to its low cost, high throughput, and high quality of the deposits, being extensively used in the magnetic recording industry to deposit relatively thick Permalloy layers, for example. In this work, electrodeposition is used to prepare Co thin films on n-type Si substrates. The semiconducting substrates used conduct sufficiently well to allow electrodeposition without the need for a seed layer, leading to the integration of a convenient method for fabricating thin magnetic films and magnetic sensors with silicon technology.Different groups have already demonstrated the feasibility of direct electrodeposition of metallic layers on Si. 1-13 In particular, we draw attention to the fact that not much work has been done on the electrodeposition of Co layers on Si͑100͒. Continuous Co layers on Si with uniform thicknesses were obtained by Pasa and Schwarzacher. 6 The authors also describe the influence of hydrogen evolution as a function of deposition potential and cobalt sulfate concentration. More recently, Cerisier et al. 9 have reported on the structure and magnetic properties of Co films electrodeposited on Si͑100͒.In this paper we investigate in detail the deposition rate, current efficiency, as well as the evolution of surface roughness of Co thin films prepared under instantaneous and progressive nucleation mechanisms. Additionally, the simultaneous measurement of the surface magnetic hysteresis and magnetoresistance allowed us to obtain the dependence of the coercive field as a function of the thickness of the samples and concentration of the electrolytes. ExperimentalThe substrates used in our experiments were single side polished, technical grade ͑100͒-oriented Si wafers n-doped for a resistivity of 1-10 ⍀ cm. Electrical contact to each substrate was made through a GaAl back contact. An adhesive tape was used ...

Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: Origin of the absence of oscillatory behavior

“…The lowest coercive field values obtained match well the data of Munford et al 59 on thick (several 100 nm) Co films electrodeposited on Si substrates. These low coercivity values can already be considered as characteristic of bulk Co with predominantly fcc structure.…”

“…It is well-known that the H c of thin ferromagnetic layers increases roughly proportionally with the inverse of the layer thickness. 59,60 Upon having put all this together, we can now return to Fig. 3 and try to explain the continuous increase of the GMR magnitude with d Cu .…”

Preparation and Characterization of Electrodeposited Cadmium and Lead thin Films from a Diluted Chloride Solution

“…It was observed that the roughness was much higher when the deposition process was denominated by progressive formation of nuclei. Therefore cadmium deposited at concentration 50ppm was rougher than cadmium obtained at concentration 200 ppm because the mechanism of nucleation was progressive at low concentration, this observation had been confirm by Minford et al [53]. The roughness of cadmium was less than lead in spite of the nucleation process is a progressive type.…”

“…The versatility of this technique allows meticulous observations and evaluations of the textural and morphological characteristics of the films, showing better facilities than other microscopic methods [52]. Table 1 The most important parameters of AFM measurements are average roughness, root mean square roughness (Sq), surface skewness, and surface kurtosis [53]. The AFM analysis of cathode substrate shows that Sq is 0.0589 nm, i.e.…”

Modifying magnetic properties of ultra-thin magnetite films by growth on Fe pre-covered MgO(001)

“…Therefore, this effect also points to a large amount of APBs. It has been reported [46][47][48] that the coercive field usually decreases with increasing film thickness. This effect has been attributed to the reduced defect density for thicker films.…”