Formation and stabilization of nanosize grains in ferromagnetic thin films by dispersed C_(60)

摘要

Thermal stability and formation of the nanostructured metal-C_(60) films have been studied. Comparative grain growth kinetic studies at 450℃ between Co-C_(60) and Co films show higher thermal stability and significantly slower grain growth in the Co-C_(60) thin film than in the Co film. Atomic force microscope observation shows that the surface of the Co film is coarsened by severe grain growth and formation of surface thermal grooves after annealing at 450℃ while the surface of the Co-C_(60) film remains smooth due to high thermal stability and slow grain growth in the film. A self-assembly grain growth mechanism is proposed to explain the formation of the uniform columnar nanosize grain structures in these ferromagnetic metal-C_(60) thin films. Estimated grain sizes based on this mechanism agree with the experimental measurement and give a relationship between the grain size and the C_(60) concentration in these films. These results indicate that C_(60) has a dual function of forming and stabilizing the nanosize grains in the metal-C_(60) films.