Alberto Alvarez-Herrero, Rosario Pardo, Marcos Zayat, and David Levy, "Ellipsometric analysis of the spectral properties and dynamic transitions of photochromic thin films," J. Opt. Soc. Am. B 24, 2097-2107 (2007)
Solgel phenyl functionalized silica thin films were used as a host matrix to embed photochromic molecules (1,3,3,5,6-pentamethyl-spiro[indoline-2--[quinolino]oxazine], 3-(2,4-dimethoxyphenyl)-3-(4-methoxyphenyl)--naphtho[2,1-b]pyran and 3,3-diphenyl--naphtho[2,1-b]pyran). The coatings were doped with individual dyes and mixtures of them. The optical properties of the colored and colorless forms of these photochromic materials were studied using variable angle spectroscopic ellipsometry. Light polarization analyses allowed an exhaustive ellipsometric characterization of these materials. Important changes were obtained in the refractive indices of the colored and colorless samples, with differences of up to 0.012 and 0.018 in the real and imaginary components, respectively. Good correlation was observed on the optical parameters of samples doped with individual dyes and mixtures of them. Standard transmission measurements were used to study the dynamic photochromic transitions and obtain the kinetic constants. The high capabilities of ellipsometry for the high-accuracy characterization of dynamic photochromic transitions were demonstrated. This technique allowed measuring variations in the populations of colored and colorless molecules, resulting from variations of temperature lower than .
Stefano Cattaneo, Steve Lecomte, Christian Bosshard, Germano Montemezzani, Peter Günter, Robert C. Livingston, and François Diederich J. Opt. Soc. Am. B 19(9) 2032-2038 (2002)
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Thickness Values of the Photochromic Films Obtained by Ellipsometry and Kinetic Constants of the Thermal Bleaching of Photochromic Samples Calculated from Transmission Measurements
Samples
Dye
Thickness (nm)
Thickness Uniform. (%)
Kinetic Measurements
Measured at (nm)
B
Blue
8.04
0.50
617
R
Red
8.60
0.66
490
Y
Yellow
28.20
1.19
443
BY
Blue–Yellow
22.15
1.26
443
6.20
0.73
617
RY
Red–Yellow
14.45
0.60
443
14.64
0.77
490
Table 2
Regression Results of the Ellipsometric Data of Samples Without UV Irradiationa
Colorless
B
R
Y
Thickness (nm)
Thickness Uniformity (%)
A
B
C
α
—
—
—
β
—
—
—
γ
—
—
—
(eV)
4.105 (fixed)
4.11 (fixed)
4.4 (fixed)
(eV)
3.943 (fixed)
3.90 (fixed)
3.904 (fixed)
(eV)
3.471 (fixed)
3.554 (fixed)
3.55 (fixed)
(eV)
2.038 (fixed)
3.413 (fixed)
3.43 (fixed)
(eV)
0.22 (fixed)
0.23 (fixed)
0.5 (fixed)
(eV)
0.14 (fixed)
0.10 (fixed)
0.06 (fixed)
(eV)
0.51 (fixed)
0.23 (fixed)
0.12 (fixed)
(eV)
0.26 (fixed)
0.12 (fixed)
0.11 (fixed)
Mean square error (MSE)
8.233
4.308
5.88
The energy centers and the broadening of the Lorentz and Gaussian oscillators were fitted and fixed from the transmission data. The final regression was carried out over the ellipsometric and transmission measurements simultaneously.
Table 3
Regression Results of the Ellipsometric Data of Samples with UV Irradiationa
The energy centers and the broadening of the Lorentz and Gaussian oscillators were fitted and fixed from the transmission data. The final regression was carried out over the ellipsometric and transmission measurements simultaneously.
G indicates Gaussian peak, otherwise it is a Lorentz peak.
Table 4
Regression Results of the Ellipsometric Data of Samples without and with UV Irradiationa
The energy centers and the broadening of the Lorentz and Gaussian oscillators were fitted and fixed from the transmission data. The final regression was carried out over the ellipsometric and transmission measurements simultaneously.
G indicates Gaussian peak, otherwise it is a Lorentz peak.
Tables (4)
Table 1
Thickness Values of the Photochromic Films Obtained by Ellipsometry and Kinetic Constants of the Thermal Bleaching of Photochromic Samples Calculated from Transmission Measurements
Samples
Dye
Thickness (nm)
Thickness Uniform. (%)
Kinetic Measurements
Measured at (nm)
B
Blue
8.04
0.50
617
R
Red
8.60
0.66
490
Y
Yellow
28.20
1.19
443
BY
Blue–Yellow
22.15
1.26
443
6.20
0.73
617
RY
Red–Yellow
14.45
0.60
443
14.64
0.77
490
Table 2
Regression Results of the Ellipsometric Data of Samples Without UV Irradiationa
Colorless
B
R
Y
Thickness (nm)
Thickness Uniformity (%)
A
B
C
α
—
—
—
β
—
—
—
γ
—
—
—
(eV)
4.105 (fixed)
4.11 (fixed)
4.4 (fixed)
(eV)
3.943 (fixed)
3.90 (fixed)
3.904 (fixed)
(eV)
3.471 (fixed)
3.554 (fixed)
3.55 (fixed)
(eV)
2.038 (fixed)
3.413 (fixed)
3.43 (fixed)
(eV)
0.22 (fixed)
0.23 (fixed)
0.5 (fixed)
(eV)
0.14 (fixed)
0.10 (fixed)
0.06 (fixed)
(eV)
0.51 (fixed)
0.23 (fixed)
0.12 (fixed)
(eV)
0.26 (fixed)
0.12 (fixed)
0.11 (fixed)
Mean square error (MSE)
8.233
4.308
5.88
The energy centers and the broadening of the Lorentz and Gaussian oscillators were fitted and fixed from the transmission data. The final regression was carried out over the ellipsometric and transmission measurements simultaneously.
Table 3
Regression Results of the Ellipsometric Data of Samples with UV Irradiationa
The energy centers and the broadening of the Lorentz and Gaussian oscillators were fitted and fixed from the transmission data. The final regression was carried out over the ellipsometric and transmission measurements simultaneously.
G indicates Gaussian peak, otherwise it is a Lorentz peak.
Table 4
Regression Results of the Ellipsometric Data of Samples without and with UV Irradiationa
The energy centers and the broadening of the Lorentz and Gaussian oscillators were fitted and fixed from the transmission data. The final regression was carried out over the ellipsometric and transmission measurements simultaneously.
G indicates Gaussian peak, otherwise it is a Lorentz peak.