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Proceedings Paper

A study of ultrathin fluoride and removable barrier films on aluminum for space-observatories with far UV observations. (Conference Presentation)
Author(s): David D. Allred; Yhoshua Wug-Jerez; R. Steven Turley; J. Gabriel Richardson; James P. Hamilton

Paper Abstract

While many materials could be used as IR mirrors, only aluminum has the potential of reaching far into the ultraviolet, as low as 85 nm. Unfortunately, Al oxidizes rapidly when it is exposed to the atmosphere, diminishing the reflectance of bare aluminum mirrors below 200 nm. For terrestrial observations, this is not a large problem, since the Earth’s atmosphere blocks radiation below this wavelength. However, mirrors used in space could use the whole range of aluminum’s reflectance, if a bare, or nearly bare mirror, could be deployed.[1] The compromise to date has been to use a thin UV-transparent, protective barrier composed of magnesium fluoride, lithium fluoride and/or aluminum fluoride. These allow the observation of the Lyman alpha line but light below 110 nm is effectively blocked. We report on our studies of ultrathin fluoride barrier layers and of removable layers which would lie on ultrathin fluoride barriers or directly on the aluminum surface. Removable barriers could be removed shortly before launch or at the mirrors point of use. These removable barriers consist of organic layers like First Contact™ or parylene, inorganic layers like amorphous silicon (a-Si), or a combination of both. We have observed, for example, that ultrathin films of AlF3 (<2.5 nm) are capable of blocking the oxidation of aluminum for several hours in air, long enough to have a removable barrier like First Contact™ applied on their surface. We also report on the effectiveness of ultrathin a-Si as a long-term barrier that may be removable via atomic hydrogen.

Paper Details

Date Published: 10 July 2018
Proc. SPIE 10699, Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray, 1069903 (10 July 2018); doi: 10.1117/12.2314382
Show Author Affiliations
David D. Allred, Brigham Young Univ. (United States)
Yhoshua Wug-Jerez, Univ. of California, Los Angeles (United States)
R. Steven Turley, Brigham Young Univ. (United States)
J. Gabriel Richardson, Brigham Young Univ. (United States)
James P. Hamilton, Nanotechnology Center for R&D (United States)

Published in SPIE Proceedings Vol. 10699:
Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray
Jan-Willem A. den Herder; Shouleh Nikzad; Kazuhiro Nakazawa, Editor(s)

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