Porosity and composition effects in sol-gel derived interference filters

B. D. Fabes; D. P. Birnie; B. J.J. Zelinski

doi:10.1016/0040-6090(94)06244-F

Porosity and composition effects in sol-gel derived interference filters

B. D. Fabes, D. P. Birnie, B. J.J. Zelinski

School of Engineering, Materials Science & Engineering

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

28 Scopus citations

Abstract

The effects of porosity and composition on the optical thickness of sol-gel films is analyzed using the Clausius-Mossotti relationship. The optical thickness is predicted to decrease with shrinkage approximately linearly. For high density films the predictions agree with experimental data from SiO₂ and SiO₂-TiO₂-Al₂O₃ coatings. At low densities, however, the optical thicknesses are much higher than predicted by the Clausius-Mossotti analysis. This difference is attributed to residual species in the unfired films. Using an empirical value for the ratio of the electronic polarizability α_r to the molecular weight W_r of the residual species ( α_r W_r = 1.65 × 10^-25cm³ mol g^-1) the difference between experiment and theory is accounted for quantitatively for both the single-component (SiO₂) and multicomponent (SiO₂-TiO₂-Al₂O₃) coatings. Approaches to fabricating multicolor dichroic filters, which require large changes in optical thickness on heating, are presented.

Original language	English (US)
Pages (from-to)	175-180
Number of pages	6
Journal	Thin Solid Films
Volume	254
Issue number	1-2
DOIs	https://doi.org/10.1016/0040-6090(94)06244-F
State	Published - Jan 1 1995

All Science Journal Classification (ASJC) codes

Electronic, Optical and Magnetic Materials
Surfaces and Interfaces
Surfaces, Coatings and Films
Metals and Alloys
Materials Chemistry

Keywords

Ceramics
Coatings
Ellipsometry
Optical coatings

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10.1016/0040-6090(94)06244-F

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title = "Porosity and composition effects in sol-gel derived interference filters",

abstract = "The effects of porosity and composition on the optical thickness of sol-gel films is analyzed using the Clausius-Mossotti relationship. The optical thickness is predicted to decrease with shrinkage approximately linearly. For high density films the predictions agree with experimental data from SiO2 and SiO2-TiO2-Al2O3 coatings. At low densities, however, the optical thicknesses are much higher than predicted by the Clausius-Mossotti analysis. This difference is attributed to residual species in the unfired films. Using an empirical value for the ratio of the electronic polarizability αr to the molecular weight Wr of the residual species ( αr Wr = 1.65 × 10-25cm3 mol g-1) the difference between experiment and theory is accounted for quantitatively for both the single-component (SiO2) and multicomponent (SiO2-TiO2-Al2O3) coatings. Approaches to fabricating multicolor dichroic filters, which require large changes in optical thickness on heating, are presented.",

keywords = "Ceramics, Coatings, Ellipsometry, Optical coatings",

author = "Fabes, {B. D.} and Birnie, {D. P.} and Zelinski, {B. J.J.}",

note = "Funding Information: The experimental data analyzed in this study were provided by Greg Lostracco and Doug Taylor. Their input, and the guiding suggestions of Sharon Melpolder, are gratefully acknowledged. Financial support has been provided generously by the Donnelly Corporation.",

year = "1995",

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day = "1",

doi = "10.1016/0040-6090(94)06244-F",

language = "English (US)",

volume = "254",

pages = "175--180",

journal = "Thin Solid Films",

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T1 - Porosity and composition effects in sol-gel derived interference filters

AU - Fabes, B. D.

AU - Birnie, D. P.

AU - Zelinski, B. J.J.

N1 - Funding Information: The experimental data analyzed in this study were provided by Greg Lostracco and Doug Taylor. Their input, and the guiding suggestions of Sharon Melpolder, are gratefully acknowledged. Financial support has been provided generously by the Donnelly Corporation.

PY - 1995/1/1

Y1 - 1995/1/1

N2 - The effects of porosity and composition on the optical thickness of sol-gel films is analyzed using the Clausius-Mossotti relationship. The optical thickness is predicted to decrease with shrinkage approximately linearly. For high density films the predictions agree with experimental data from SiO2 and SiO2-TiO2-Al2O3 coatings. At low densities, however, the optical thicknesses are much higher than predicted by the Clausius-Mossotti analysis. This difference is attributed to residual species in the unfired films. Using an empirical value for the ratio of the electronic polarizability αr to the molecular weight Wr of the residual species ( αr Wr = 1.65 × 10-25cm3 mol g-1) the difference between experiment and theory is accounted for quantitatively for both the single-component (SiO2) and multicomponent (SiO2-TiO2-Al2O3) coatings. Approaches to fabricating multicolor dichroic filters, which require large changes in optical thickness on heating, are presented.

AB - The effects of porosity and composition on the optical thickness of sol-gel films is analyzed using the Clausius-Mossotti relationship. The optical thickness is predicted to decrease with shrinkage approximately linearly. For high density films the predictions agree with experimental data from SiO2 and SiO2-TiO2-Al2O3 coatings. At low densities, however, the optical thicknesses are much higher than predicted by the Clausius-Mossotti analysis. This difference is attributed to residual species in the unfired films. Using an empirical value for the ratio of the electronic polarizability αr to the molecular weight Wr of the residual species ( αr Wr = 1.65 × 10-25cm3 mol g-1) the difference between experiment and theory is accounted for quantitatively for both the single-component (SiO2) and multicomponent (SiO2-TiO2-Al2O3) coatings. Approaches to fabricating multicolor dichroic filters, which require large changes in optical thickness on heating, are presented.

KW - Ceramics

KW - Coatings

KW - Ellipsometry

KW - Optical coatings

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JO - Thin Solid Films

JF - Thin Solid Films

IS - 1-2

ER -

Porosity and composition effects in sol-gel derived interference filters

Abstract

All Science Journal Classification (ASJC) codes

Keywords

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