Thermal hysteresis measurement of the VO 2 dielectric function for its metal-insulator transition by visible-IR ellipsometry

J. Ramirez-Rincon 1, 2 C. Gomez-Heredia 1, 2 A. Corvisier 1 J. Ordonez-Miranda 1 T. Girardeau 1, 3 F. Paumier 1, 3 C. Champeaux 4 F. Dumas-Bouchiat 4 Y. Ezzahri 1, 5 K. Joulain 1, 5 O. Ares 2 J. Alvarado-Gil 2, 1
3 PPNa - Physique et Propriétés des Nanostructures PPNa
Département Physique et Mécanique des Matériaux - Département Physique et Mécanique des Matériaux
4 IRCER-AXE2 - IRCER - Axe 2 : procédés plasmas et lasers
IRCER - Institut de Recherche sur les CERamiques : AXE2
5 TNR - Thermique aux Nano échelles et Rayonnement
FTC - Département Fluides, Thermique et Combustion
Abstract : The real and imaginary parts of the dielectric function of VO2 thin films, deposited on r-plane sapphire via pulsed laser deposition, are measured by means of visible-infrared ellipsometry for wavelengths ranging from 0.4 to 15 μm and temperatures within its phase transition. For both the insulator-to-metal (heating) and metal-to-insulator (cooling) transitions, it is shown that the two ellipsometric signals exhibit three temperature-driven behaviors, which are well described by appropriate combinations of the Tauc-Lorentz, Gaussian, and Drude oscillator models. By fitting Bruggeman's effective medium model for the dielectric function to the corresponding measured experimental values, using the volumetric fraction of the VO2 metallic domains as a fitting parameter for different temperatures within the VO2 phase transition, we have found that this model is suitable for describing the dielectric function in visible and near-infrared wavelengths (∼0.4 to ∼3.0 μm), but it generally fails for longer infrared ones. Furthermore, the hysteresis loop of the VO2 emissivity averaged over a relevant interval of wavelengths is determined and shown to vary from ∼0.49, in the insulator phase, to ∼0.16, in the metallic one. These values, based on the VO2 dielectric function, are consistent with previous measurements reported in the literature, and therefore, our measured data are expected to be useful for describing the behavior of VO2 films involved in optical and radiative applications.
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Contributeur : Beatrice Derory <>
Soumis le : lundi 13 mai 2019 - 15:59:22
Dernière modification le : lundi 16 septembre 2019 - 15:19:08

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J. Ramirez-Rincon, C. Gomez-Heredia, A. Corvisier, J. Ordonez-Miranda, T. Girardeau, et al.. Thermal hysteresis measurement of the VO 2 dielectric function for its metal-insulator transition by visible-IR ellipsometry. Journal of Applied Physics, American Institute of Physics, 2018, 124 (19), pp.195102. ⟨10.1063/1.5049747⟩. ⟨hal-02127642⟩

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