Title

Corrosion Protection Of Front Surface Aluminum Mirror Coatings With Dielectric Thin Films Deposited By Reactive Ion Plating

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.

Publication Date

1-8-1990

Publication Title

Proceedings of SPIE - The International Society for Optical Engineering

Volume

1125

Number of Pages

114-121

Document Type

Article; Proceedings Paper

Personal Identifier

scopus

DOI Link

https://doi.org/10.1117/12.961363

Socpus ID

85075458912 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85075458912

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