Stability of samples in coating research: From edge effect to ageing

Lumaca, D.; Amato, A.; Bischi, M.; Cagnoli, G.; Cesarini, E.; Fafone, V.; Guidi, G. M.; Lorenzini, M.; Martelli, F.; Mereni, L.; Minenkov, Y.; Montani, M.; Nardecchia, I.; Piergiovanni, F.; Placidi, E.; Rocchi, A.

doi:10.1016/j.jallcom.2022.167320

Cited by 2 publications

(2 citation statements)

References 17 publications

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“…Figures 4(b) and (c) show the relative coating loss angle variation as a function of the coating crystalline fraction, for the so-called butterfly and mixed vibrational modes of different shapes [27]. Indeed, as shown by figure 4(a), in all our (φ c ) i data series we observe a branching of butterfly and mixed modes, likely due to a systematic effect of the raw, coated edge of the sample [15,27,28]. However, as figures 4(b) and (c) show, such branching does not affect the observed general trend of the coating loss angle against annealing, which is the same for all modes, and can then be neglected.…”

Section: Loss Angle Measurementsmentioning

confidence: 61%

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Reduction of mechanical losses in ion-beam sputtered tantalum oxide thin films via partial crystallization

Favaro,

Milotti,

Alonso Diaz Riega

et al. 2024

Class. Quantum Grav.

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This study explores the impact of crystalline fraction on the mechanical losses of amorphous tantalum oxide (tantala, Ta2O5) thin films intended for gravitational wave detectors. We use ion beam sputtering (IBS) technique to prepare a series of samples, which are then subjected to controlled thermal annealing to achieve varying degrees of crystallized fraction. The microscopic structure of the annealed samples is characterized by combining different analytical techniques. Our investigation reveals that the amorphous films comprise randomly distributed crystalline grains, whose density and average size depends on the duration of thermal treatment. To assess mechanical losses of the coatings, a Gentle Nodal Suspension (GeNS) system is applied. Remarkably, a substantial reduction of approximately 20% in the coating’s mechanical loss angle with respect to annealed amorphous coatings is observed for samples exhibiting a crystalline fraction of around 5%. This improvement may lead to the definition of alternative thermal treatments to improve the mechanical performances of coatings for gravitational wave detectors or other highly sensitive optical experiments. However the reduction in mechanical losses comes at the expense of an increase in optical scattering. The possibility of reducing the optical losses to the level required by gravitational interferometers by modifying the grain size distribution via appropriate annealing treatments is discussed.

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Section: Loss Angle Measurementsmentioning

confidence: 61%

“…In this case a single sample was characterized for loss angle before and after each annealing step. We performed the sensitive mechanical loss measurements immediately after the thermal treatment, in order to avoid any spurious, uncontrolled ageing effect [15].…”

Section: Sample Stepmentioning

confidence: 99%