Improvement in the homogeneity of molybdenium coatings deposited onto polished polycrystalline molybdenium substrates

Abstract

The surface morphology of optical sputter-resistant nanocrystal molybdenum coatings formed by magnetron sputtering is investigated. The coatings deposited onto polished polycrystalline molybdenum mirrors have defects of two types: large crystalline inclusions protruding above the coating surface and areas with sharp boundaries corresponding to those of grains on the polycrystalline substrate surface. Preliminary treatment of the substrate surface by sputtering with the simultaneous deposition of substrate material removed defects of both types. A theoretical model of coating formation explaining the mechanism of improvement in its structural uniformity during surface preparation by the proposed method is presented.