Increased durability of sol–gel derived MgF2 antireflective coatings capped by vapor deposition

Porous MgF2 antireflective λ/4 films were prepared by sol–gel processing and coated with an additional top layer by electron beam evaporation. Scanning Electron Microscopy was applied to characterize the microstructure of the bilayer assembly. It can be shown that the top layer has a protective effect in terms of abrasion resistance and reduced solubility in water. In a second step the thickness of the two film systems has been matched to achieve optimum antireflection properties.