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Investigation of effects of assisted ion bombardment on mechanical loss of sputtered tantala thin films for gravitational wave interferometers

Yang, Le and Randel, Emmett and Vajente, Gabriele and Ananyeva, Alena and Gustafson, Eric and Markosyan, Ashot and Bassiri, Riccardo and Fejer, Martin M. and Menoni, Carmen S. (2019) Investigation of effects of assisted ion bombardment on mechanical loss of sputtered tantala thin films for gravitational wave interferometers. Physical Review D, 100 (12). Art. No. 122004. ISSN 2470-0010. doi:10.1103/physrevd.100.122004.

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Reduction of Brownian thermal noise due to mechanical loss in high-reflectivity mirror coatings is critical for improving the sensitivity of future gravitational wave detectors. In these mirrors, the mechanical loss at room temperature is dominated by the high refractive index component, amorphous tantala (Ta₂O₅) or tantala doped with titania (Ti∶Ta₂O₅). Toward the goal of identifying mechanisms that could alter mechanical loss, this work investigates the use of assist ion bombardment in the reactive ion beam sputtering deposition of tantala single layers. Low-energy assist ion bombardment can enhance adatom diffusion. Low-energy assist Ar⁺ and Xe⁺ ion bombardment at different conditions was implemented during deposition to identify trends in the mechanical loss with ion mass, ion energy, and ion dose. It is shown that the atomic structure and bonding states of the tantala thin films are not significantly modified by low-energy assist ion bombardment. The coatings mechanical loss remains unaltered by ion bombardment within errors. Based on an analysis of surface diffusivity, it is shown that the dominant deposition of tantala clusters and limited surface diffusion length of oxygen atoms constrain structural changes in the tantala films. A slower deposition rate coupled with a significant increase in the dose of the low-energy assist ions may provide more favorable conditions to improve adatom diffusivity.

Item Type:Article
Related URLs:
URLURL TypeDescription
Yang, Le0000-0002-8868-5977
Vajente, Gabriele0000-0002-7656-6882
Fejer, Martin M.0000-0002-5512-1905
Menoni, Carmen S.0000-0001-9185-2572
Additional Information:© 2019 American Physical Society. (Received 11 June 2019; published 11 December 2019) This work is supported by the National Science Foundation LIGO program through Grant No. 1710957. We also acknowledge the support of the LIGO Scientific Collaboration (LSC) Center for Coatings Research, jointly funded by the National Science Foundation (NSF) and the Gordon and Betty Moore Foundation.
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
LIGO Scientific Collaboration CenterUNSPECIFIED
Issue or Number:12
Record Number:CaltechAUTHORS:20191212-105210743
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100274
Deposited By: George Porter
Deposited On:12 Dec 2019 22:33
Last Modified:16 Nov 2021 17:52

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