Effect of process variables on the structure, residual stress, and hardness of sputtered nanocrystalline nickel films

Nanocrystalline nickel films of about 0.1 μm thickness grown by sputtering with and without substrate bias possessed average grain sizes of 9–25 nm. Variation in substrate bias at room and liquid nitrogen temperature of deposition strongly affected grain structure and size distribution. Qualitative studies of film surfaces showed variation in roughness and porosity level with substrate bias and film thickness (maximum of 8 μm). The films had tensile residual stress, which varied with deposition conditions. The hardness values were much higher than those of coarse-grained nickel but decreased with an increase in the film thickness because of grain growth.