Structural and optical characterization of amorphous and crystalline evaporated WO3 layers

Antonaia, A.; Polichetti, T.; Addonizio, M.L.; Aprea, S.; Minarini, Carla; Rubino, Alfredo

doi:10.1016/s0040-6090(99)00567-2

Cited by 64 publications

(31 citation statements)

References 9 publications

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“…5,31,32,57 However, many authors indicated that a single Gaussian line shape cannot completely account for the optical properties of colored WO 3 . 33,55,58,59 Our analysis reveals that the polaron-induced DF changes in colored amorphous tungsten oxide films is excellently characterized for charge densities between x = 0 , . .…”

Section: B Polaron Propertiesmentioning

confidence: 78%

“…2,32,56,57 It has already been observed that a single Gaussian or Lorentzian line shape is not fully sufficient to describe the experimentally observed absorption behavior. 33,55,58,59 Here we obtain that polaron-induced DF changes in colored tungsten oxide film must be modeled by two separate oscillators with Lorentzian and Gaussian line shapes. We identify these oscillators with the transitions between W 4+ and W 5+ and between W 5+ and W 6+ states, respectively, as described below.…”

Section: Polaron Contributionmentioning

confidence: 83%

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Polaron and phonon properties in proton intercalated amorphous tungsten oxide thin films

et al. 2008

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We report on the evolution of the polaron and phonon mode properties in amorphous tungsten oxide thin films measured by spectroscopic ellipsometry in the infrared to ultraviolet spectral regions as a function of the intercalated proton density. A parametric physical model dielectric function is presented, which excellently describes the ellipsometry data over a large intercalated charge-density range. Upon increased amounts of intercalated charge we observe a strong increase in the polaron absorption in the visible spectral range, a decrease in the infrared W-O bond polarity, and an increase in the W = O bond polarity. Our findings support the oxygen-extraction model as the polaron formation mechanism in tungsten oxide in agreement with previous theoretical works based on first-principles pseudopotential calculations. We discuss and suggest polaron formation by oxygen-related defect generation as origin for the coloration mechanism in tungsten oxide. We further discuss possible evidence for very large effective mass of the polarons within the insulator-to-metal transition regime.

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Section: B Polaron Propertiesmentioning

confidence: 78%

Section: Polaron Contributionmentioning

confidence: 83%

Polaron and phonon properties in proton intercalated amorphous tungsten oxide thin films

et al. 2008

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“…Volatilization of WO 3 in vacuum (10 -5 mbar) is reported by Antonaia et al during their study on chemical vapor deposition of WO 3 on glass substrate [34]. From above discussion, it can be said that UWO 6 is not stable above 1173 K in Ar atmosphere as well as in vacuum and decomposes to U 2 WO 8 ?…”

Section: Thermal Expansionmentioning

confidence: 83%

Studies on thermophysical properties of ThW2O8 and UWO6

Keskar

Krishnan

Phatak

et al. 2016

J Therm Anal Calorim

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Thermal stability and expansion behavior of ThW 2 O 8 and UWO 6 were studied using thermogravimetry and high-temperature X-ray diffraction techniques. ThW 2-O 8 and UWO 6 showed positive thermal expansion in vacuum from ambient to 1273 and 1073 K, respectively. Heat capacity for ThW 2 O 8 (s) and UWO 6 (s) was measured in argon atmosphere using heat flux-type differential scanning calorimeter, and thermodynamic functions of these compounds have been computed from the measured heat capacity data. The structural study of UWO 6 was also carried out from powder X-ray diffraction data using Rietveld profile method.

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“…The rectification effect decreases, in good agreement with the protonic mobility decrease, after the 300°C annealing. It is well known that at about such temperature, the water molecules leave the amorphous structure of the metal oxide films, but the transition to a crystalline compacted phase occurs only for higher temperature treatments [14]; furthermore, the extending crystalline order after dehydration do not improve the protonic conductivity, while enhancing remarkably the electronic conductivity of such film, as demonstrated by coloring experiments after different annealing temperatures [15]. By Raman investigation, it was confirmed that the films annealed at 100°C and those annealed at 300°C are still amorphous, while the 600°C annealing induces the formation of anhydrous ordered phases, with a remarkable increase of the electrical conductivity, as indicated by the impedance measurements [9][10]12].…”

Section: Discussionmentioning

confidence: 99%

Electro-optical response due to mixed conduction electrodes, compared to ferroelectric ones, in asymmetric nematic liquid crystal cells

Castriota

Marino

Strangi

et al. 2008

Ionics

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The usual liquid crystal cells show an electrooptical response symmetric to the applied voltage. On the contrary, when mixed conduction films such as tungsten trioxide or vanadium pentoxide are inserted on one side of the cell, the electro-optical response is asymmetric with respect to the applied voltage. Depending on the structural phase of the inserted film the electro-optical response is in phase (transmission ON during the anodic polarization on metal oxide electrode, transmission OFF during the cathodic one) or in opposition of phase (reverse combination). The first case has been explained by the formation of a double charge layer at the interface metal oxide-liquid crystal, because of migration of protons contained in the oxide films. The other case has been found after hightemperature treatments of metal oxides deposited on glass-ITO substrates, and it appears quite similar to the response collected by using films of ferroelectric materials such as lead zirconium titanate (PZT). This fact suggests a possible interpretation in terms of dielectric response, when the mixed conduction films undergo high-temperature treatments. A comparative study of films of WO 3 , V 2 O 5 , and PZT is carried out in this work as a function of the annealing temperature.

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Structural and optical characterization of amorphous and crystalline evaporated WO3 layers

Cited by 64 publications

References 9 publications

Polaron and phonon properties in proton intercalated amorphous tungsten oxide thin films

Polaron and phonon properties in proton intercalated amorphous tungsten oxide thin films

Studies on thermophysical properties of ThW2O8 and UWO6

Electro-optical response due to mixed conduction electrodes, compared to ferroelectric ones, in asymmetric nematic liquid crystal cells

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