DIAMOND PROTECTIVE COATINGS FOR OPTICAL-COMPONENTS

The use of polycrystalline diamond films as protective coatings on IR materials has been highlighted as a major application of CVD diamond t echnology. However, those materials which would benefit most from diam ond coatings, such as ZnS and Ge, possess vastly different thermomecha nical properties. The severe technological problems which exist have p revented commercialization to the levels achieved by heat sinks and cu tting tools. We have been working for some time on the direct depositi on of diamond onto protected ZnS windows and have extended our process to include other IR materials. By employing void-free protective inte rlayers we have produced diamond films up to 1 mum thick on planar int erlayers on ZnS. Lithographic substrate patterning has been used to ex ceed this barrier and increase the achievable thickness towards the le vels required for true protection from water drop or particulate erosi on. Deposition onto sapphire substrates has permitted considerable pro gress in overcoming mechanical problems in isolation from chemical pro blems present with ZnS in an aggressive plasma. The aspects of substra te preparation, adhesion and stress relief are discussed. The optical and structural properties of diamond-coated samples are presented.