Effects of the annealing of amorphous Ta2O5 coatings produced by ion beam sputtering concerning the effusion of argon and the chemical composition

Paolone, A.; Placidi, E.; Stellino, Elena; Betti, Maria Grazia; Majorana, E.; Mariani, Carlo; Nucara, A.; Palumbo, O.; Postorino, P.; Rago, Ilaria; Trequattrini, F.; Teillon, Julien; Hofman, D.; Michel, C.; Lemaı̂tre, Anaël; Shcheblanov, N. S.; Cagnoli, G.; Ricci, F.

doi:10.1016/j.jnoncrysol.2021.120651

Cited by 14 publications

(19 citation statements)

References 27 publications

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“…Changes of the intermediate range structure were also found in TiO 2 -Ta 2 O 5 amorphous coatings [23]. More recently, the presence of argon in Ta 2 O 5 due to the synthesis by IBS was reported [24]. Ar can be released by heating above 300 • C [24].…”

Section: Introductionmentioning

confidence: 85%

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Argon and Other Defects in Amorphous SiO2 Coatings for Gravitational-Wave Detectors

et al. 2022

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Amorphous SiO2 thin films are one of the two components of the highly reflective mirror coatings of gravitational-wave detectors. For this study, layers of amorphous SiO2 on crystalline Si substrates were produced by ion-beam sputtering (IBS), using accelerated neutralized argon ions as sputtering particles, as is the case for the actual mirror coatings of gravitational-wave detectors. The aim of this study is to investigate the possible presence of various defects in the materials in order to improve the coating quality. We provide evidence that, due to the synthesis method, about 0.2 wt.% of Ar is present in the coatings, and it can be released by means of thermal treatments, starting around 400 °C. The time and temperature to obtain the total release of Ar increases with the coating thickness; for a thickness of 100 nm, all argon is released below 600 °C, while an isotherm of one hour at 900 °C is necessary for a coating 5 μm thick. Besides the Ar atoms left from the synthesis, other defects, such as Si clusters and silicon dangling bonds, are present in the coatings. The concentration of both of them is strongly reduced by thermal treatments either in vacuum or in air. The overall thickness of the coating is slightly increased after thermal treatments, as witnessed by the change of the period of interference fringes.

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Section: Introductionmentioning

confidence: 85%

“…More recently, the presence of argon in Ta 2 O 5 due to the synthesis by IBS was reported [24]. Ar can be released by heating above 300 • C [24]. It was reported that the density of Ta 2 O 5 decreases as the annealing temperature increases [24].…”

Section: Introductionmentioning

confidence: 99%

Argon and Other Defects in Amorphous SiO2 Coatings for Gravitational-Wave Detectors

et al. 2022

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“…The same samples, however, featured an unusually high value of scattering, 45 ppm, compared to that of present detectors (5 ppm) [27,46]. Indeed, part of the observed excess scatter might be ascribed to the presence of Ar bubbles formed upon annealing [29,43,70].…”

Section: Discussionmentioning

confidence: 45%

Exploration of co-sputtered Ta₂O₅–ZrO₂ thin films for gravitational-wave detectors

Abernathy

Amato

Ananyeva

et al. 2021

Class. Quantum Grav.

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We report on the development and extensive characterization of co-sputtered tantala-zirconia (Ta 2 O 5 -ZrO 2 ) thin films, with the goal to decrease coating Brownian noise in present and future gravitational-wave detectors. We tested a variety of sputtering processes of different energies and deposition rates, and we considered the effect of different values of cation ratio η = Zr/(Zr + Ta) and of post-deposition heat treatment temperature T a on the optical and mechanical properties of the films. Co-sputtered zirconia proved to be an efficient way to frustrate crystallization in tantala thin films, allowing for a substantial increase of the maximum annealing temperature and hence for a decrease of coating mechanical loss ϕ c . The lowest average coating loss was observed for an ion-beam sputtered sample with η = 0.485 ± 0.004 annealed at 800 • C, yielding ϕ c = 1.8 × 10 −4 rad. All coating samples showed cracks after annealing. Although in principle our measurements are sensitive to such defects, we found no evidence that our results were affected. The issue could be solved, at least for ion-beam sputtered coatings, by decreasing heating and cooling rates down to 7 • C h −1 . While we observed as little optical absorption as in the coatings of current gravitational-wave interferometers (0.5 parts per million), further development will be needed to decrease light scattering and avoid the formation of defects upon annealing.

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“…At least for some IBS samples (LMA), we found that the formation of cracks could be avoided by decreasing the annealing heating and cooling rates down to 7 • C/h. Nevertheless, starting from T a = 500 • C, bubble-like defects of different number and size, detected with an optical microscope, appeared at variable depth in the IBS HR coating samples, likely due to the presence of incorporated argon within the layers [6,42,49]. We observed no trace of such defects in the annealed IBS single-layer annealed samples deposited under strictly identical conditions, indicating that this phenomenon only occurs when layers are stacked.…”

Section: Effects Of Annealingmentioning

confidence: 60%

Exploration of co-sputtered Ta$_2$O$_5$-ZrO$_2$ thin films for gravitational-wave detectors

Abernathy,

Amato,

Ananyeva

et al. 2021

Preprint

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We report on the development and extensive characterization of cosputtered tantala-zirconia thin films, with the goal to decrease coating Brownian noise in present and future gravitational-wave detectors. We tested a variety of sputtering processes of different energies and deposition rates, and we considered the effect of different values of cation ratio η = Zr/(Zr+Ta) and of post-deposition heat treatment temperature T a on the optical and mechanical properties of the films. Co-sputtered zirconia proved to be an efficient way to frustrate crystallization in tantala thin films, allowing for a substantial increase of the maximum annealing temperature and hence for a decrease of coating mechanical loss. The lowest average coating loss was observed for an ion-beam sputtered sample with η = 0.485 ± 0.004 annealed at 800 • C, yielding ϕ = 1.8 × 10 −4 . All coating samples showed cracks after annealing. Although in principle our measurements are sensitive to such defects, we found no evidence that our results were affected. The issue could be solved, at least for ion-beam sputtered coatings, by decreasing heating and cooling rates down to 7 • C/h. While we observed as little optical absorption as in the coatings of current gravitational-wave interferometers (0.5 parts per million), further development will be needed to decrease light scattering and avoid the formation of defects upon annealing.

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Effects of the annealing of amorphous Ta2O5 coatings produced by ion beam sputtering concerning the effusion of argon and the chemical composition

Cited by 14 publications

References 27 publications

Argon and Other Defects in Amorphous SiO2 Coatings for Gravitational-Wave Detectors

Argon and Other Defects in Amorphous SiO2 Coatings for Gravitational-Wave Detectors

Exploration of co-sputtered Ta₂O₅–ZrO₂ thin films for gravitational-wave detectors

Exploration of co-sputtered Ta$_2$O$_5$-ZrO$_2$ thin films for gravitational-wave detectors

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Effects of the annealing of amorphous Ta2O5 coatings produced by ion beam sputtering concerning the effusion of argon and the chemical composition

Cited by 14 publications

References 27 publications

Argon and Other Defects in Amorphous SiO2 Coatings for Gravitational-Wave Detectors

Argon and Other Defects in Amorphous SiO2 Coatings for Gravitational-Wave Detectors

Exploration of co-sputtered Ta2O5–ZrO2 thin films for gravitational-wave detectors

Exploration of co-sputtered Ta$_2$O$_5$-ZrO$_2$ thin films for gravitational-wave detectors

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Exploration of co-sputtered Ta₂O₅–ZrO₂ thin films for gravitational-wave detectors