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

In the majority of modern IR interference multilayer coatings (MI-C), conve ntional film-forming materials (FFM) of fluoride and chalcogenide types are used. Such coatings are characterized by relatively low mechanical strengt h and stability against enhanced humidity and, therefore, require surface p rotection. 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 h ardness 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 sp ectrum microanalysis, The resistance of DLC films applied onto MLC against light irradiation, organic solvents as well as against environmental factor s was also studied. Atomic force microscopy (AFM) was used to study variati ons of the surface morphology of the initial MLC components before and afte r DLC film deposition. (C) 2001 Elsevier Science B.V. All rights reserved.