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Ar transport and blister growth kinetics in titania-doped germania-based optical coatings

Émile Lalande, Aaron Davenport, Lory Marchand, Ashot Markosyan, Daniel Martı́nez, Annalisa Paolone, Michael Rezac, Marco Bazzan, Martin Chicoine, Julien L. Colaux, Matthieu Coulon, Martin M. Fejer, Alexandre W. Lussier, Ettore Majorana, Ludvik Martinu, Carmen Menoni, Christophe Michel, Fulvio Ricci, François Schiettekatte, Nikita S. Shcheblanov, Joshua R. Smith, Julien Teillon, Guy Terwagne and Gabriele Vajente

Article (2024)

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Abstract

Blistering is a phenomenon sometimes observed in sputtered-deposited thin films but seldom investigated in detail. Here, we consider the case of titania-doped germania (TGO)/silica multilayers deposited by ion beam sputtering. TGO is a candidate as high refractive index material in the Bragg mirrors for the next iteration of gravitational waves detectors. It needs to be annealed at 600 °C for 100 h in order to reach the desired relaxation state. However under some growth conditions, in 52-layer TGO/silica stacks, blistering occurs upon annealing at a temperature near 500 °C, which corresponds to the temperature where Ar desorbs from TGO. In order to better understand the blistering phenomenon, we measure the Ar transport in single layers of TGO and silica. In the case of 1 µm-thick TGO layers, the Ar desorption is mainly limited by detrapping. The transport model also correctly predicts the evolution of the total amount of Ar in a 8.5 µm stack of TGO and silica layers annealed at 450 °C, but in that case, the process is mainly limited by diffusion. Since Ar diffusion is an order of magnitude slower in TGO compared to silica, we observe a correspondingly strong accumulation of Ar in TGO. The Ar transport model is used to explain some regimes of the blisters growth, and we find indications that Ar accumulation is a driver for their growth in general, but the blisters nucleation remains a complex phenomenon influenced by several other factors including stress, substrate roughness, and impurities.

Uncontrolled Keywords

blistering; argon; annealing; thermal desorption; ion beam analysis; scatterometer; bragg reflector

Subjects: 3100 Physics > 3100 Physics
Department: Department of Engineering Physics
Funders: NSERC / CRSNG, Canada Foundation for Innovation (CFI), Fonds de recherche Québec - Nature et technologies (FQRNT), Projet de coopération Québec-Wallonie-Bruxelles, National Science Foundation (NSF) - Award, Dan Black Family Trust, Nancy and Lee Begovich
Grant number: PHY-2207998, PHY-1807069, PHY-0757058, PHY-0823459, Wallonie: #RECH-INNO-02, Québec: #11.802
PolyPublie URL: https://publications.polymtl.ca/58185/
Journal Title: Classical and Quantum Gravity (vol. 41, no. 11)
Publisher: IOP Publishing
DOI: 10.1088/1361-6382/ad3ffb
Official URL: https://doi.org/10.1088/1361-6382/ad3ffb
Date Deposited: 24 May 2024 08:34
Last Modified: 27 Jun 2024 01:50
Cite in APA 7: Lalande, É., Davenport, A., Marchand, L., Markosyan, A., Martı́nez, D., Paolone, A., Rezac, M., Bazzan, M., Chicoine, M., Colaux, J. L., Coulon, M., Fejer, M. M., Lussier, A. W., Majorana, E., Martinu, L., Menoni, C., Michel, C., Ricci, F., Schiettekatte, F., ... Vajente, G. (2024). Ar transport and blister growth kinetics in titania-doped germania-based optical coatings. Classical and Quantum Gravity, 41(11), 115013 (31 pages). https://doi.org/10.1088/1361-6382/ad3ffb

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