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Proceedings Paper

Application of germanium carbide in durable multilayer IR coatings
Author(s): Chris J. Kelly; James S. Orr; H. Gordon; Leonard T. Traub; Alan H. Lettington
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Paper 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.

Paper Details

Date Published: 1 August 1990
PDF: 13 pages
Proc. SPIE 1275, Hard Materials in Optics, (1 August 1990); doi: 10.1117/12.20524
Show Author Affiliations
Chris J. Kelly, OCLI Optical Coatings Ltd. (United Kingdom)
James S. Orr, OCLI Optical Coatings Ltd. (United Kingdom)
H. Gordon, OCLI Optical Coatings Ltd. (United Kingdom)
Leonard T. Traub, OCLI Optical Coatings Ltd. (United Kingdom)
Alan H. Lettington, Royal Signals and Radar Establishment (United Kingdom)

Published in SPIE Proceedings Vol. 1275:
Hard Materials in Optics
Carl-Gustaf Ribbing, Editor(s)

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