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Proceedings Paper

Corrosion Protection Of Front Surface Aluminum Mirror Coatings With Dielectric Thin Films Deposited By Reactive Ion Plating
Author(s): Karl H. Guenther; lain Penny; Ron Willey
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Paper Abstract

Front surface metal mirrors need protection of the inherently fragile metal film normally deposited by evaporation in high vacuum. Dielectric thin films, also deposited by thermal or electron beam evaporation in high vacuum, provide limited protection because of their less than dense packing. These films usually have a columnar structure with voids between the columns. The voids give access to the metal film for humidity and corrosive gases or liquids. Sainty et al. [Appl. Opt. 23, 1116 (1984)] made some progress in developing better protective coatings with ion assisted deposition. We manufactured protected front surface aluminum mirrors using reactive ion plating deposition. When immersed in 0.2M NaOH, our best mirror survived for 20 hours while only degrading to a transmission of 10%, exceeding the results of Sainty et al. by a factor of 5 under the same test conditions. Electron beam evaporated dielectric coatings provided protection for about 1.5 to 2 hours in the same solution. We will discuss the reason for the significant improvement brought about by low voltage reactive ion plating deposition, and its advantage for large scale production.

Paper Details

Date Published: 8 January 1990
PDF: 8 pages
Proc. SPIE 1125, Thin Films in Optics, (8 January 1990); doi: 10.1117/12.961363
Show Author Affiliations
Karl H. Guenther, University of Central Florida (United States)
lain Penny, University of Central Florida (United States)
Ron Willey, Opto Mechanik, Inc. (United States)

Published in SPIE Proceedings Vol. 1125:
Thin Films in Optics
Theo T. Tschudi, Editor(s)

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