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Proceedings Paper

Current progress in the characterization of atomic layer deposited AlF3 for future astronomical ultraviolet mirror coatings
Author(s): Christopher Samuel Moore; John Hennessy; Eliot Kersgaard; April D. Jewell; Shouleh Nikzad; Kevin France
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Paper Abstract

Reflective aluminum (Al) mirrors for astronomical telescopes are traditionally protected by a transmissive overcoat. The optical, mechanical and chemical properties of this overcoat material strongly affect the spectral reflective properties and durability of the mirror system. We are developing atomic layer deposited metal fluorides and assessing their applicability for future astronomical space missions in the ultraviolet and visible wavelengths. We are currently performing depositions on silicon wafers to serve as a basis for the metal-fluoride on Al depositions. In this paper we present reflectance, surface roughness, environmental storage and polarization sensitivity results of thin layers of AlF3 on silicon. Atomic layer deposited coatings of AlF3 grown at 100 and 200 °C yield good optical characteristics deduced from reflectance measurements from 90 – 800 nm and spectroscopic ellipsometry measurements from 200 – 800 nm, which are consistent with calculations from optical constants derived by our group and from the literature. Atomic force microscopy (AFM) measurements demonstrate a 15% increase in surface roughness for a ~25 nm film with respect to a silicon reference. Temporary storage in a gN2 box minimally affects the UV reflectance of ~30 nm of AlF3 on Si. Overall, these coatings have proven to be versatile and optically stable in the early phases of development.

Paper Details

Date Published: 24 August 2015
PDF: 15 pages
Proc. SPIE 9601, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XIX, 96010X (24 August 2015); doi: 10.1117/12.2186723
Show Author Affiliations
Christopher Samuel Moore, Univ. of Colorado at Boulder (United States)
John Hennessy, Jet Propulsion Lab. (United States)
Eliot Kersgaard, Univ. of Colorado at Boulder (United States)
April D. Jewell, Jet Propulsion Lab. (United States)
Shouleh Nikzad, Jet Propulsion Lab. (United States)
Kevin France, Univ. of Colorado at Boulder (United States)

Published in SPIE Proceedings Vol. 9601:
UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XIX
Oswald H. Siegmund, Editor(s)

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