Adolf Canillas, Frank Güell, Oriol Arteaga, Paulina R. Martínez-Alanis, Michel Vergnat, Hervé Rinnert, and Blas Garrido, "Dielectric function of vanadium oxide thin films by thermal annealing," Appl. Opt. 60, 4477-4484 (2021)
The dielectric function of ${{\rm{VO}}_x}$ and ${{\rm{V}}_2}{{\rm{O}}_5}$ thin films is determined with the use of a spectroscopic Mueller matrix ellipsometer from 1.5 to 5.0 eV. The complex dielectric function of the films is calculated using the measured Mueller matrices filtered with the Cloude decomposition. ${{\rm{VO}}_x}$ shows high absorption in the UV region, a Tauc–Lorentz gap around 2.4 eV, and non-vanishing absorption in the visible. ${{\rm{V}}_2}{{\rm{O}}_5}$ shows a high absorption band centered at 2.87 eV, an indirect optical band gap at 1.95 eV, and a direct optical band gap at 2.33 eV. The ellipsometric characterization is supported by Raman, x-ray photoelectron, and photoluminescence spectroscopy.
Taixing Huang, Lin Yang, Jun Qin, Fei Huang, Xupeng Zhu, Peiheng Zhou, Bo Peng, Huigao Duan, Longjiang Deng, and Lei Bi Opt. Mater. Express 6(11) 3609-3621 (2016)
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
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Reduced and Best-Fit Parameters, with Their 95% Confidence Limit, Corresponding to an Isotropic Model with a Dielectric Function Given by a TL Oscillator and Two LOsa,b
Sample
A
B
C
0.96
1.6
7.2
(nm)
(nm)
(eV)
(eV)
C (eV)
(eV)
(eV)
(eV)
(eV)
A value of 50% for Samples A and B and 25% for Sample C has been taken as the void fraction of the surface roughness.
Thickness of the surface roughness (${d}_r$), thickness of the bulk layer (${d}_l$), high frequency dielectric constant (${\varepsilon _\infty}$), TL gap (${E}_G$), central TL energy (${{E}_0}$), strength (${{A}}_L$) and broadening (C) of the ${\varepsilon _2}$ TL peak, central energy (${E}_i$), damping factor ($\gamma_i$) and oscillator strength parameter (${{f}}_i$) of the LOs.
Table 4.
Optical Model Refinements for Sample C Assuming a TL Oscillator and Three LOs (TL + 3LO) or Two TL Oscillators and Two LOs (2TL + 2LO)a
Model
TL + 3LOs
2TL + 2LOs
4.4
1.3
(nm)
(nm)
(eV)
(eV)
(eV)
(eV)
–
–
(eV)
–
(eV)
(eV)
(eV)
(eV)
(eV)
–
(eV)
–
–
See Table 3, footnote b, for the description of the parameters.
Reduced and Best-Fit Parameters, with Their 95% Confidence Limit, Corresponding to an Isotropic Model with a Dielectric Function Given by a TL Oscillator and Two LOsa,b
Sample
A
B
C
0.96
1.6
7.2
(nm)
(nm)
(eV)
(eV)
C (eV)
(eV)
(eV)
(eV)
(eV)
A value of 50% for Samples A and B and 25% for Sample C has been taken as the void fraction of the surface roughness.
Thickness of the surface roughness (${d}_r$), thickness of the bulk layer (${d}_l$), high frequency dielectric constant (${\varepsilon _\infty}$), TL gap (${E}_G$), central TL energy (${{E}_0}$), strength (${{A}}_L$) and broadening (C) of the ${\varepsilon _2}$ TL peak, central energy (${E}_i$), damping factor ($\gamma_i$) and oscillator strength parameter (${{f}}_i$) of the LOs.
Table 4.
Optical Model Refinements for Sample C Assuming a TL Oscillator and Three LOs (TL + 3LO) or Two TL Oscillators and Two LOs (2TL + 2LO)a
Model
TL + 3LOs
2TL + 2LOs
4.4
1.3
(nm)
(nm)
(eV)
(eV)
(eV)
(eV)
–
–
(eV)
–
(eV)
(eV)
(eV)
(eV)
(eV)
–
(eV)
–
–
See Table 3, footnote b, for the description of the parameters.