Characterization of evaporated amorphous WO3 films by Raman and FTIR spectroscopies

Shigesato, Yuzo; Murayama, Akihiro; Kamimori, Tadatoshi; Matsuhiro, Kenji

doi:10.1016/0169-4332(88)90384-4

Cited by 105 publications

(40 citation statements)

References 12 publications

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“…Two peaks present on the anodic-HT (Figure 3a). The broad peak at 770 cm −1 is ascribed to the stretching mode of W-O 27 and the distinct peak at 958 cm −1 is assigned to the stretching mode of W = O of the terminal oxygen. 28 The peaks belong to the amorphous hydrated WO 3 .…”

Section: Resultsmentioning

confidence: 99%

A WO₃Nanoporous-Nanorod Film Formed by Hydrothermal Growth of Nanorods on Anodized Nanoporous Substrate

Razak

Lockman

2015

J. Electrochem. Soc.

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A tungsten oxide (WO 3 ) nanoporous-nanorod film was produced for the first time by hydrothermally growing WO 3 nanorods on nanoporous WO 3 substrate. The nanoporous substrates were prepared using the anodization method; hydrothermal reaction was performed on as-anodized and annealed (200-500 • C) nanoporous substrates for nanorod growth. The as-anodized substrate and the substrates annealed at ≤300 • C dissolved after hydrothermal reaction because of the amorphous and low crystallinity behaviors of the WO 3 substrates. However, the substrates annealed at ≥400 • C did not dissolve during the hydrothermal reaction; instead, nanorods were grown on the substrates, forming a nanoporous-nanorod structure. The WO 3 nanoporous-nanorod film (nanorods grown on substrate annealed at 400 • C) showed good electrochromic properties with high current density (−13.22 and +7.30 mA cm −2 ), good cycling stability, and short coloring (∼6 s) and bleaching (∼3.4 s) times. These good properties are attributed to the combination of two nanostructures (nanoporous and nanorods) that contributed to a large WO 3 surface area. Tungsten oxide (WO 3 ) is a well-known electrochromic material that has the ability to reversibly change color between colorless and blue with the application of electric potential. One of the important criteria to obtain good electrochromic property is the large surface area of the electrochromic material. A large surface area increases the interaction between the electrochromic material and electrolyte (H + or Li + ), which results in faster ion and electron intercalation and de-intercalation processes. A nanostructured electrochromic material is advantageous because of its large surface area. In producing nanostructured WO 3 films, all reported research works have yielded single nanostructured WO 3 film; no combination of WO 3 nanostructures in a film has been reported. The combination of two WO 3 nanostructures is postulated to exhibit the unique properties of both nanostructures, thereby enhancing the electrochromic properties. A WO 3 film comprising two nanostructures is introduced in this work. WO 3 nanorods were grown on a nanoporous WO 3 substrate to form a WO 3 nanoporous-nanorod film. The combination of these structures is hypothesized to produce good electrochromic properties, as the resulting structure possesses a large total surface area of WO 3 (open nanoporous structure and one-dimensional nanorods), which allows more ion and electron intercalation to occur.Porous WO 3 can be synthesized by template-assisted 1 and anodization 2-4 methods. The template-assisted method could produce ordered porous WO 3 , but with large pore diameter size of ∼330 nm. This method also requires several steps to obtain the final porous WO 3 product. Synthesis is initiated by preparing polystyrene sphere monolayer colloidal crystal on a glass slide, followed by transfer of the colloidal crystal template from the glass slide onto a substrate. Tungstic acid solution is then dropped onto the template-substrate, and calcination...

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Section: Resultsmentioning

confidence: 99%

A WO₃Nanoporous-Nanorod Film Formed by Hydrothermal Growth of Nanorods on Anodized Nanoporous Substrate

Razak

Lockman

2015

J. Electrochem. Soc.

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“…The variations of content of WO 2 and W inside unavoidably change crystal symmetry of WO 3 . However, referring to the previous work [19], the stress due to mismatch and the different thermal expansion between the substrate and overlayer is qualitatively associated with increasing the shift and width of the band. The blue shifts of the samples are also due to the high stress of particles caused by the high temperature's deposition process.…”

Section: Grows and Characterizationsmentioning

confidence: 99%

Ambient Pressure Synthesis of Nanostructured Tungsten Oxide Crystalline Films

Zhang

Yang

Feng

2008

Journal of Nanomaterials

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We report the results of the ambient pressure synthesis of tungsten oxide nanowires and nanoparticles on AlN substrates using the hot filament CVD techniques. The morphologic surface, crystallographic structures, chemical compositions, and bond structures of the obtained samples have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and Raman scattering, respectively. Different morphologies were observed for different substrate temperatures, but otherwise identical growth conditions. The experimental measurements reveal the evolutions of the crystalline states and bond structures following the substrate temperatures. Besides, different substrate materials also affected the tungsten oxide nanostructures. Bundles of wire-type tungsten oxide nanowires with a length of up to 5 mm were obtained on Al 2 O 3 substrate. Furthermore, the sensitive properties of the super long nanowires to the gas and different temperature were investigated. The dependence of the sensitivity of tungsten oxide nanowires to the methane as a function of the time was obtained. The sensitive properties of the tungsten oxide nanowires have almost linear relationship with the temperature.

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“…The third component is associated with the stretching vibration of W ‫ס‬ O terminal bonds, reported to be present at the surface of atomic clusters. 18 The second band (Band II) is observed to contain two components at 1430 and 1630 cm −1 , and the third band (Band III) appears to contain four components at 2800, 3000, 3200, and 3400 cm −1 . These two bands are associated with the H-O-H deformation and H-O stretching vibration respectively, and are not observed in bulk WO 3 crystal.…”

Section: B Structurementioning

confidence: 99%

“…15,16 The second component is close to the two IR bands of crystalline WO 3 (at 800 or 807 cm −1 ). 17,18 The appearance of these two components indicates that the amorphous network in RTE1 has a short range order analogous to that in crystalline WO 3 . The third component is associated with the stretching vibration of W ‫ס‬ O terminal bonds, reported to be present at the surface of atomic clusters.…”

Section: B Structurementioning

confidence: 99%

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Relationship between the microstructure and nanoindentation hardness of thermally evaporated and magnetron-sputtered electrochromic tungsten oxide films

et al. 2001

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Tungsten oxide (WO x ) films were fabricated by (i) reactive thermal evaporation (RTE) at room temperature with oxygen ambient pressure P O 2 as a parameter, and (ii) reactive magnetron sputtering (RMS) with substrate temperature T s as a parameter. The film structure revealed by x-ray photoelectron spectroscopy, x-ray diffraction, density measurements, infrared absorption, and atomic force microscopy was correlated with the nanoindentation hardness H. The RTE WO x films deposited at high P O 2 were amorphous and porous, while H depended appreciably on normalized penetration depth h D (indentation depth/film thickness) due to the closing of the pores at the point of indentation. Decrease in P O 2 from 10 to 2 × 10 −3 mtorr led to smaller porosity, weaker h D dependence of H, and higher average H (measured at h D ≈ 0.2 to 0.3, for example). The RMS WO x film deposited at room temperature was amorphous and denser than all RTE films. The rise in substrate temperature T s first densified the film structure (up to 110°C) and then induced crystallization with larger grain size for T s ജ 300°C. Correspondingly, the h D dependence of H became weaker. In particular, H of the RMS sample deposited at 110°C showed a peak at h D slightly above 1 owing to pileup at the contact point of indentation. For higher T s , pileup occurred at shallower h D and the average H (measured at h D ≈ 0.2 to 0.3, for example) rose, accompanied by the increase of grain size.

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Characterization of evaporated amorphous WO3 films by Raman and FTIR spectroscopies

Cited by 105 publications

References 12 publications

A WO₃Nanoporous-Nanorod Film Formed by Hydrothermal Growth of Nanorods on Anodized Nanoporous Substrate

A WO₃Nanoporous-Nanorod Film Formed by Hydrothermal Growth of Nanorods on Anodized Nanoporous Substrate

Ambient Pressure Synthesis of Nanostructured Tungsten Oxide Crystalline Films

Relationship between the microstructure and nanoindentation hardness of thermally evaporated and magnetron-sputtered electrochromic tungsten oxide films

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Characterization of evaporated amorphous WO3 films by Raman and FTIR spectroscopies

Cited by 105 publications

References 12 publications

A WO3Nanoporous-Nanorod Film Formed by Hydrothermal Growth of Nanorods on Anodized Nanoporous Substrate

A WO3Nanoporous-Nanorod Film Formed by Hydrothermal Growth of Nanorods on Anodized Nanoporous Substrate

Ambient Pressure Synthesis of Nanostructured Tungsten Oxide Crystalline Films

Relationship between the microstructure and nanoindentation hardness of thermally evaporated and magnetron-sputtered electrochromic tungsten oxide films

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A WO₃Nanoporous-Nanorod Film Formed by Hydrothermal Growth of Nanorods on Anodized Nanoporous Substrate

A WO₃Nanoporous-Nanorod Film Formed by Hydrothermal Growth of Nanorods on Anodized Nanoporous Substrate