Effect of Thickness on the Structural, Microstructural, Electrical and Magnetic Properties of Ni Films Elaborated By Pulsed Electrodeposition on Si Substrate

Abstract

We have studied the effect of thickness on the structural, microstructural, electrical and magnetic properties of Ni films electrodeposited onto n-Si (100) substrates. A series of Ni films have been prepared for different potentials ranging from -1.6V to -2.6V. Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), four point probe technique, atomic force microscopy (AFM) and vibrating sample magnetometry (VSM) have been used to investigate the physical properties of elaborated Ni thin films. From the analysis of RBS spectra, we have extracted the films thickness t (t ranges from 83nm to 422 nm). We found that the Ni thickness, t (nm), linearly increases with the applied potential. The Ni thin films are polycrystalline and grow with the < 111 > texture. The lattice parameter a (angstrom) monotonously decreases with increasing thickness. However, a positive strain was noted indicating that all the samples are subjected to a tensile stress. The mean grain sizes D (nm) and the strain epsilon(hkl) decrease with increasing thickness. The electrical resistivity rho (mu Omega.cm) increases with t for t less than 328 nm. The diffusion at the grain boundaries may be the important factor in the electrical resistivity. From AFM images, we have shown that the Ni surface roughness decreases with increasing thickness. The coercive field H-C, the squareness factor S, the saturation field H-S and the effective anisotropy constant K-1eff are investigated as a function of Ni thickness and grain sizes. The correlation between the magnetic and the structural properties is discussed.