Effect of intermediate layers on atomic layer deposition-aluminum oxide protected silver mirrors

David M. Fryauf; Juan J. Diaz Leon; Andrew C. Phillips; Nobuhiko P. Kobayashi

doi:10.1117/1.JATIS.3.3.034001

9 September 2017 Effect of intermediate layers on atomic layer deposition-aluminum oxide protected silver mirrors

David M. Fryauf, Juan J. Diaz Leon, Andrew C. Phillips, Nobuhiko P. Kobayashi

Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 3, Issue 3, 034001 (September 2017). https://doi.org/10.1117/1.JATIS.3.3.034001

Abstract

This work investigates intermediate materials deposited between silver (Ag) thin-film mirrors and an aluminum oxide (AlO_x) barrier overlayer and compares the effects on mirror durability to environmental stresses. Physical vapor deposition of various fluorides, oxides, and nitrides in combination with AlO_x by atomic layer deposition (ALD) is used to develop several coating recipes. Ag-AlO_x samples with different intermediate materials undergo aggressive high-temperature (80°C), high-humidity (80%) (HTHH) testing for 10 days. Reflectivity of mirror samples is measured before and after HTHH testing, and image processing techniques are used to analyze the specular surface of the samples after HTHH testing. Among the seven intermediate materials used in this work, TiN, MgAl₂O₄, NiO, and Al₂O₃ intermediate layers offer more robust protection against chemical corrosion and moisture when compared with samples with no intermediate layer. In addition, results show that the performance of the ALD-AlO_x barrier overlayer depends significantly on the ALD-growth process temperature. Because higher durability is observed in samples with less transparent TiN and NiO layers, we propose a figure of merit based on post-HTHH testing reflectivity change and specular reflective mirror surface area remaining after HTHH testing to judge overall barrier performance.

Citation Download Citation

David M. Fryauf, Juan J. Diaz Leon, Andrew C. Phillips, and Nobuhiko P. Kobayashi "Effect of intermediate layers on atomic layer deposition-aluminum oxide protected silver mirrors," Journal of Astronomical Telescopes, Instruments, and Systems 3(3), 034001 (9 September 2017). https://doi.org/10.1117/1.JATIS.3.3.034001

Received: 1 February 2017; Accepted: 24 May 2017; Published: 9 September 2017

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