Interaction of surface energy and grain boundary energy during the growth of Au/NiCr/Ta film

Au/NiCr/Ta multi-layered metallic films were deposited on Al2O3 substrate by magnetron sputtering. The surface morphology and surface roughness of the multi-layered films were examined with Atomic Force Microscopy (AFM). The dependence of surface roughness on deposition temperature was identified in the terms of energy theory. It is found that the metallic film grew in the form of column grains by magnetron sputtering. With increasing the deposition temperature, the surface morphology transformed from rough to smooth, then to rough. This can be explained with the model of surface diffusion and grain aggregation. It was clarified that the complex interaction of surface energy and grain boundary energy is the fundamental reason for the change of surface roughness.