Magnetron sputtered oxidation resistant and antireflection protective coatings for freestanding diamond film IR windows

It is well known that the CVD diamond films start to oxidize at temperatures above 700 degrees C, which may restrict their use in high temperature oxidation environment, such as for IR windows and cutting tools. Due to its high refractive index, the maximum transmission of diamond film is limited to approximately 71%. In the present investigation, HfO2 and Y2O3 coatings were prepared by reactive magnetron sputtering of pure Hf and Y metal target in Ar+O-2 atmosphere. Adherent HfO2 and Y2O3 coatings on high optical quality diamond film samples with optimum thickness for IR transmission enhancement in 8-12 mu m and 3-5 mu m were obtained. More than 20% increase in transmission was observed for both HfO2/Diamond/HfO2 and Y2O3/Diamond/Y2O3 coating systems. Excellent oxidation resistance for HfO2/Diamond/HfO2 and Y2O3/Diamond Y2O3 coatings were demonstrated at temperatures up to 950 degrees C in oxidation environment. (C) 2008 Elsevier B.V. All rights reserved.