Diamond-like carbon films in multilayered interference coatings for IR optical elements

In the majority of modern IR interference multilayer coatings (MI-C), conventional film-forming materials (FFM) of fluoride and chalcogenide types are used. Such coatings are characterized by relatively low mechanical strength and stability against enhanced humidity and, therefore, require surface protection. Our present results support the view that mechanical strength of these MLCs can be improved by applying a diamond-like carbon (DLC) film as an external layer. Nanoindentation measurements show that the addition of a DLC film to ZnSe/BaF2/Y2O3 IR antireflection MLC increases the combined hardness of the coatings from 0.5 to 3.6 GPa. The formation of an indent on the upper and subsequent layers of MLC has been studied by SEM and X-ray spectrum microanalysis, The resistance of DLC films applied onto MLC against light irradiation, organic solvents as well as against environmental factors was also studied. Atomic force microscopy (AFM) was used to study variations of the surface morphology of the initial MLC components before and after DLC film deposition. (C) 2001 Elsevier Science B.V. All rights reserved.