Effect of Growth Temperature on the Structural, Morphological, and Magnetic Properties of Sputtered Ni Thin Film

Abstract

In this work, nickel thin film with thickness of 35 nm was grown by radio frequency sputtering on a Si/SiO₂ substrate as a function of growth temperature from 100°C to 350°C. The effect of substrate temperature during film growth was extensively investigated with regard to the structural, morphological, and dynamic magnetic properties of the grown films. The films were polycrystalline with a face-centered cubic (FCC) structure, as evident from the different diffraction peaks. The saturation magnetization (M_S) was greatest and coercivity (H_C) was observed to be lowest for films grown at 250°C. The Gilbert damping (\({\alpha }_{{\rm eff}}\)) and effective magnetization (\({M}_{{\rm eff}}\)) as a function of growth temperature were obtained from microwave-induced ferromagnetic resonance (FMR) spectroscopy measurements. \({\alpha }_{{\rm eff}}\) derived from FMR line widths, which is an important parameter for quantifying ferromagnetic film quality, was lowest at 250°C and increased on either side of this point. The lowest damping at 250°C indicates low strain and defect density at this temperature, which is also evident from x-ray diffraction (XRD) data. \({M}_{{\rm eff}}\) also increased and reached a maximum at 250°C growth temperature. The decrease in magnetization below and above 250°C indicates diffusion and formation of a magnetic dead layer at the substrate–film interface. These measurements reveal that a narrow growth temperature regime exists for the growth of Ni thin film to obtain films with low defects, and hence low Gilbert damping, which can be utilized in spintronics device applications.