Investigation of the Young’s modulus and thermal expansion of amorphous titania-doped tantala films

Abernathy, M. R., Hough, J. , Martin, I. W. , Rowan, S. , Oyen, M., Linn, C. and Faller, J. E. (2014) Investigation of the Young’s modulus and thermal expansion of amorphous titania-doped tantala films. Applied Optics, 53(15), pp. 3196-3202. (doi: 10.1364/AO.53.003196) (PMID:24922204)

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The current generation of advanced gravitational wave detectors utilize titania-doped tantala/silica multilayer stacks for their mirror coatings. The properties of the low-refractive-index silica are well known; however, in the absence of detailed direct measurements, the material parameters of Young’s modulus and coefficient of thermal expansion (CTE) of the high refractive index material, titania-doped tantala, have been assumed to be equal to values measured for pure tantala coatings. In order to ascertain the true values necessary for thermal noise calculations, we have undertaken measurements of Young’s modulus and CTE through the use of nanoindentation and thermal-bending measurements. The measurements were designed to assess the effects of titania-doping concentration and post-deposition heat-treatment on the measured values in order to evaluate the possibility of optimizing material parameters to further improve thermal noise in the detector. Young’s modulus measurements on pure tantala and 25% and 55% titania-doped tantala show a wide range of values, from 132 to 177 GPa, which are dependent on both titania concentration and heat-treatment. Measurements of CTE give values of (3.9±0.1)×10<sup>−6</sup>  K<sup>−1</sup> and (4.9±0.3)×10<sup>−6</sup>  K<sup>−1</sup> for 25% and 55% titania-doped tantala, respectively, without dependence on post-deposition heat-treatment.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Rowan, Professor Sheila and Abernathy, Mr Matthew and Martin, Dr Iain and Hough, Professor James and Faller, Professor James
Authors: Abernathy, M. R., Hough, J., Martin, I. W., Rowan, S., Oyen, M., Linn, C., and Faller, J. E.
College/School:College of Science and Engineering > School of Physics and Astronomy
Research Centre:College of Science and Engineering > School of Physics and Astronomy > Institute for Gravitational Research
Journal Name:Applied Optics
Journal Abbr.:Appl. Opt.
Publisher:Optical Society of America
ISSN (Online):2155-3165
Copyright Holders:Copyright © 2014 Optical Society of America
First Published:First published in Applied Optics 53(15):3196-3202
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
459313Investigations in Gravitational Radiation.Sheila RowanScience & Technologies Facilities Council (STFC)ST/J000361/1P&A - PHYSICS & ASTRONOMY
624341Investigations in Gravitational RadiationSheila RowanScience & Technologies Facilities Council (STFC)ST/L000946/1S&E P&A - PHYSICS & ASTRONOMY