Effects of Coatings on the Optical Scatter and Related Roughness of Coated Surfaces

The effects of coatings on the optical scatter and surface microroughness have been investigated by many authors recently. In previous publications [1-3] we have presented experimental results which indicate that coated surfaces, under certain conditions, may be smoother than the bare substrate. For example, it was reported that coating a polished copper (Cu) surface with a thin, 0.1 to 1 um, Cu film caused a significant reduction optical scatter and related surface microroughness. Different factors such as film thickness, deposition conditions, and the microroughness of the substrate, determined the magnitude of surface smoothing. In this report we present experimental results that illustrate the role of deposition mechanism and substrate morphology in the smoothing of coated surfaces. A model for the smoothing process will be presented.