Application of germanium carbide in durable multilayer IR coatings

Chris J. Kelly; James S. Orr; H. Gordon; Leonard T. Traub; Alan H. Lettington

doi:10.1117/12.20524

1 August 1990 Application of germanium carbide in durable multilayer IR coatings

Chris J. Kelly, James S. Orr, H. Gordon, Leonard T. Traub, Alan H. Lettington

Proceedings Volume 1275, Hard Materials in Optics; (1990) https://doi.org/10.1117/12.20524
Event: The International Congress on Optical Science and Engineering, 1990, The Hague, Netherlands

Abstract

Infrared transparent amorphous hydrogenated alloys of germanium and carbon (germanium carbide) have been deposited by plasma assisted chemical vapour deposition (PACVD) using germane (GeH4 ) and butane (C 4Hid as the feedstocks and by reactive sputtering of germanium with a CH1g-Ar plasma. The effects of varying various deposition conditions have been assessed on a number of coating properties . Germanium Carbide has good environmental durability and can be deposited in thick layers. Using PACVD it can be deposited with any refractive index in the range 2 to 4 while the sputtering process is limited to indices in the range 3 to 4 . One advantage of the sputtering process is the high deposition rates achievable which can be up to '-lOum/h compared with lum/h for the PACVD process. When used in conjunction with "diamond-like" carbon (a-'C:H) , germanium carbide offers the prospect of rnultilayer antireflection coatings for 8 to 12 urn optics with durabilities which hitherto have been impossible to achieve. Antireflection coatings for zinc sulphide windows which are subject to hostile environmental conditions have been investigated and the performance of the coatings is presented. The factors affecting the practical realisation of these coatings on a production scale are discussed.

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Chris J. Kelly, James S. Orr, H. Gordon, Leonard T. Traub, and Alan H. Lettington "Application of germanium carbide in durable multilayer IR coatings", Proc. SPIE 1275, Hard Materials in Optics, (1 August 1990); https://doi.org/10.1117/12.20524

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