Effect of sputtering pressure and power on composition, surface roughness, microstructure and magnetic properties of as-deposited Co2FeSi thin films

The effect of sputtering pressure and power on the composition, surface roughness, structure, microstructure and magnetic properties of full Heusler type Co2FeSi films deposited on silicon (001) substrates at room temperature using DC magnetron sputtering technique was studied. The composition of the film was found to be influenced by both sputtering pressure and power. The films deposited at lower pressures (0.667-2 Pa) and lower power (50-75 W), which result in lower deposition rates, have compositions comparable with that of the target. The surface roughness of the films was found to be significantly affected by a change in sputtering pressure but not by a variation in sputtering power. Irrespective of the sputtering pressure and power, all the as-deposited Co-2 FeSi/Si(001) films exhibited A2 type disordered nanocrystalline structure. The grain size, however, was found to increase marginally with an increase in sputtering pressure and power. Analysis of magnetization curves of the films revealed that the films were soft ferromagnetic for all sputtering pressures and power. However, the coercivities, magnetization values and reversibility of zero field cooling and field cooling magnetization curves were found to depend critically on sputtering parameters. (C) 2014 Elsevier B. V. All rights reserved.