The role of microstructure on the optical performance of neutron irradiated dielectric mirrors

Keith J. Leonard; Gerald E. Jellison; N. A.P.Kiran Kumar; Lance L. Snead

doi:10.1016/j.jnucmat.2013.11.022

The role of microstructure on the optical performance of neutron irradiated dielectric mirrors

Keith J. Leonard
, Gerald E. Jellison
, N. A.P.Kiran Kumar
, Lance L. Snead

Materials Science and Engineering

Oak Ridge National Laboratory

Research output: Contribution to journal › Article › peer-review

12 Scopus citations

Abstract

Dielectric mirrors of HfO₂/SiO₂ and Al ₂O₃/SiO₂ designed for optimum reflectivity at 248 nm with 11 and 30 bi-layer coatings, respectively, survived irradiation to 0.1 dpa at 448 K without film cracking or delamination from their sapphire substrates. Subsequent annealing of the irradiated samples resulted in a loss of reflectivity in the HfO₂/SiO₂ mirror, while the Al ₂O₃/SiO₂ type remained unaffected. Microstructural changes that correlate to optical property changes of the mirror are investigated. The amorphous layers of the Al₂O ₃/SiO₂ mirror provide greater stability despite increased Al and Si interdiffusion across the film interfaces with increasing dose and post-irradiation annealing temperature. This interdiffusion may have limited the densification of SiO₂ in the Al₂O₃/SiO ₂ mirror, but no interdiffusion was observed for the HfO ₂/SiO₂ mirror. The thickness changes in the SiO ₂ layers of the HfO₂/SiO₂ mirror resulted in a shifting of the peak reflectivity to lower wavelengths. The formation of an amorphous Al-O layer within the substrate is observed in the 0.1 dpa irradiated HfO₂/SiO₂ mirror, which on further annealing at 573 and 673 K resulted in a buckling-type delamination failures in the mirrors producing a loss in reflectivity.

Original language	English
Pages (from-to)	281-290
Number of pages	10
Journal	Journal of Nuclear Materials
Volume	445
Issue number	1-3
DOIs	https://doi.org/10.1016/j.jnucmat.2013.11.022
State	Published - Feb 2014

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title = "The role of microstructure on the optical performance of neutron irradiated dielectric mirrors",

abstract = "Dielectric mirrors of HfO2/SiO2 and Al 2O3/SiO2 designed for optimum reflectivity at 248 nm with 11 and 30 bi-layer coatings, respectively, survived irradiation to 0.1 dpa at 448 K without film cracking or delamination from their sapphire substrates. Subsequent annealing of the irradiated samples resulted in a loss of reflectivity in the HfO2/SiO2 mirror, while the Al 2O3/SiO2 type remained unaffected. Microstructural changes that correlate to optical property changes of the mirror are investigated. The amorphous layers of the Al2O 3/SiO2 mirror provide greater stability despite increased Al and Si interdiffusion across the film interfaces with increasing dose and post-irradiation annealing temperature. This interdiffusion may have limited the densification of SiO2 in the Al2O3/SiO 2 mirror, but no interdiffusion was observed for the HfO 2/SiO2 mirror. The thickness changes in the SiO 2 layers of the HfO2/SiO2 mirror resulted in a shifting of the peak reflectivity to lower wavelengths. The formation of an amorphous Al-O layer within the substrate is observed in the 0.1 dpa irradiated HfO2/SiO2 mirror, which on further annealing at 573 and 673 K resulted in a buckling-type delamination failures in the mirrors producing a loss in reflectivity.",

author = "Leonard, \{Keith J.\} and Jellison, \{Gerald E.\} and Kumar, \{N. A.P.Kiran\} and Snead, \{Lance L.\}",

year = "2014",

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doi = "10.1016/j.jnucmat.2013.11.022",

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T1 - The role of microstructure on the optical performance of neutron irradiated dielectric mirrors

AU - Leonard, Keith J.

AU - Jellison, Gerald E.

AU - Kumar, N. A.P.Kiran

AU - Snead, Lance L.

PY - 2014/2

Y1 - 2014/2

N2 - Dielectric mirrors of HfO2/SiO2 and Al 2O3/SiO2 designed for optimum reflectivity at 248 nm with 11 and 30 bi-layer coatings, respectively, survived irradiation to 0.1 dpa at 448 K without film cracking or delamination from their sapphire substrates. Subsequent annealing of the irradiated samples resulted in a loss of reflectivity in the HfO2/SiO2 mirror, while the Al 2O3/SiO2 type remained unaffected. Microstructural changes that correlate to optical property changes of the mirror are investigated. The amorphous layers of the Al2O 3/SiO2 mirror provide greater stability despite increased Al and Si interdiffusion across the film interfaces with increasing dose and post-irradiation annealing temperature. This interdiffusion may have limited the densification of SiO2 in the Al2O3/SiO 2 mirror, but no interdiffusion was observed for the HfO 2/SiO2 mirror. The thickness changes in the SiO 2 layers of the HfO2/SiO2 mirror resulted in a shifting of the peak reflectivity to lower wavelengths. The formation of an amorphous Al-O layer within the substrate is observed in the 0.1 dpa irradiated HfO2/SiO2 mirror, which on further annealing at 573 and 673 K resulted in a buckling-type delamination failures in the mirrors producing a loss in reflectivity.

AB - Dielectric mirrors of HfO2/SiO2 and Al 2O3/SiO2 designed for optimum reflectivity at 248 nm with 11 and 30 bi-layer coatings, respectively, survived irradiation to 0.1 dpa at 448 K without film cracking or delamination from their sapphire substrates. Subsequent annealing of the irradiated samples resulted in a loss of reflectivity in the HfO2/SiO2 mirror, while the Al 2O3/SiO2 type remained unaffected. Microstructural changes that correlate to optical property changes of the mirror are investigated. The amorphous layers of the Al2O 3/SiO2 mirror provide greater stability despite increased Al and Si interdiffusion across the film interfaces with increasing dose and post-irradiation annealing temperature. This interdiffusion may have limited the densification of SiO2 in the Al2O3/SiO 2 mirror, but no interdiffusion was observed for the HfO 2/SiO2 mirror. The thickness changes in the SiO 2 layers of the HfO2/SiO2 mirror resulted in a shifting of the peak reflectivity to lower wavelengths. The formation of an amorphous Al-O layer within the substrate is observed in the 0.1 dpa irradiated HfO2/SiO2 mirror, which on further annealing at 573 and 673 K resulted in a buckling-type delamination failures in the mirrors producing a loss in reflectivity.

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SN - 0022-3115

VL - 445

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JO - Journal of Nuclear Materials

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ER -

The role of microstructure on the optical performance of neutron irradiated dielectric mirrors

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