Influence of effective surface area on gas sensing properties of WO3 sputtered thin films

Shen, Yanbai; Yamazaki, Toshinari; Liu, Zhifu; Meng, Dan; Kikuta, Toshio; Nakatani, N.

doi:10.1016/j.tsf.2008.10.021

Cited by 151 publications

(54 citation statements)

References 25 publications

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“…Although pure WO 3 is a recognized candidate for gasochromic, electrochromic, and photochromic devices, its morphological characteristics are strongly dependent on the conditions and methods used in its fabrication, as revealed in the literature [1][2][3][4][5][6][7][8][9][10]. An improvement in its gasochromic detection sensitivity and in its increased temperature range of operation as a sensor, which for undoped thin films of WO 3 grown by radio-frequency (RF) magnetron sputtering are achieved at a deposition temperature of *200°C [9,10], as well as in its electrochromic and photocatalytic properties, has been achieved by doping with appropriate metals or by addition of metal/metal oxide additives [7][8][9][10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

“…An improvement in its gasochromic detection sensitivity and in its increased temperature range of operation as a sensor, which for undoped thin films of WO 3 grown by radio-frequency (RF) magnetron sputtering are achieved at a deposition temperature of *200°C [9,10], as well as in its electrochromic and photocatalytic properties, has been achieved by doping with appropriate metals or by addition of metal/metal oxide additives [7][8][9][10][11][12][13][14][15][16][17][18]. Due to electron transfer from the metal oxide to the added metal on its surface, a decrease in the electron concentration in the metal oxide surface layer occurs.…”

Section: Introductionmentioning

confidence: 99%

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Comparative microscopic and spectroscopic analysis of temperature-dependent growth of WO3 and W0.95Ti0.05O3 thin films

et al. 2012

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We present a comparative microscopic and spectroscopic study of the morphology and composition of WO 3 and W 0.95 Ti 0.05 O 3 thin films, grown by radio-frequency magnetron reactive sputtering at substrate temperatures varied from room temperature to 500°C, using atomic force microscopy (AFM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). With increasing growth temperature, the AFM results show increase in the average crystallite size and in the surface roughness for both undoped and doped samples. The AFM data, along with the Raman results, clearly indicate that for the given set of experimental conditions, higher growth temperatures are required to obtain crystalline Ti-doped WO 3 films than for WO 3 films. Also, the Raman results suggest a potential phase transformation from a monoclinic WO 3 structure to an orthorhombic, but more probably a tetragonal, configuration in the W 0.95 Ti 0.05 O 3 thin films. This remark is based on the observed shifting, with Ti doping, to lower frequencies of the Raman peaks corresponding to W-O-W stretching modes of WO 3 at 806 and 711 cm -1 to 793 and 690 cm -1 , respectively. XPS data indicate that the doped material has a reduced WO 3-x stoichiometry at the surface, with the presence of W 6? and W 5? oxidation states; this observation could also be related to the existence of a different structural phase of this material, corroborating with the Raman measurements.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparative microscopic and spectroscopic analysis of temperature-dependent growth of WO3 and W0.95Ti0.05O3 thin films

et al. 2012

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“…We studied gas sensors made of sputteredˆlms of various oxide semiconductors, such as SnO 2 , 4-7) WO 3 , [8][9][10] and MoO 3 . 11) Bearing the Thornton diagram in mind, we depositedˆlms under various discharge gas pressures and substrate temperatures and attempted to qualitatively evaluate theˆlm porosity by measuring thê lm density.…”

Section: Introductionmentioning

confidence: 99%

“…This method was applied to WO 3 sputteredˆlms in our previous study, 9,10) in which, however, the measurement of surface area was performed mostly for annealedˆlms. The measurement was performed forˆlms deposited at a high pressure of 20 Pa and annealed at diŠerent temperatures 9) and forˆlms deposited at diŠerent pressures and annealed at 600°C.…”

Section: Introductionmentioning

confidence: 99%

“…The measurement was performed forˆlms deposited at a high pressure of 20 Pa and annealed at diŠerent temperatures 9) and forˆlms deposited at diŠerent pressures and annealed at 600°C. 10) Thus, for further understanding of the microstructure of sputtered WO 3ˆl ms, we measured the surface area together with the density more systematically with both the discharge gas pressure and annealing temperature adopted as parameters.…”

Section: Introductionmentioning

confidence: 99%

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Nanostructure of WO3 Sputtered Films Deposited at Various Gas Pressures

et al. 2010

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Deep investigations were performed for further understanding of the nanostructure of sputtered WO 3ˆl ms. The as-depositedˆlms consisted ofˆne crystallites of several nm. As the pressure increased, theˆlm density decreased and the surface area increased owing to open pores between grains. Whenˆlms were annealed at 400°C or above, they were well crystallized to form monoclinic and randomly-shaped grains. Upon this crystallization, theˆlm shrank and its density increased slightly, while the relative surface area substantially decreased.

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Methane Detection with a Tungsten‐Calix[4]arene‐Based Conducting Polymer Embedded Sensor Array

Luo

et al. 2020

Adv Funct Materials

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The detection of methane is important for industry, environment, and our daily life, but is made challenging by its small size, high volatility, and nonpolar nature. Herein, a tungsten‐capped calix[4]arene‐based p‐doped conducting polymer with hexafluorophosphate or perchlorate counter‐anions as a transducer is used to detect methane in dry air. The host–guest interaction between calixarene moieties within the polymer chain and methane molecules leads to the resistance variation of the polymer. The experimental limit of detection (LoD) of methane for the polymer‐based sensor is demonstrated to be less than 50 ppm at room temperature, and the extrapolated theoretical LoD of 2 ppm represents exceptional sensitivity to methane. Furthermore, the discrimination of methane from interfering volatile organic compounds is achieved by exploiting a sensor array using complementary chemiresistors and principal component analysis.

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Influence of effective surface area on gas sensing properties of WO3 sputtered thin films

Cited by 151 publications

References 25 publications

Comparative microscopic and spectroscopic analysis of temperature-dependent growth of WO3 and W0.95Ti0.05O3 thin films

Comparative microscopic and spectroscopic analysis of temperature-dependent growth of WO3 and W0.95Ti0.05O3 thin films

Nanostructure of WO3 Sputtered Films Deposited at Various Gas Pressures

Methane Detection with a Tungsten‐Calix[4]arene‐Based Conducting Polymer Embedded Sensor Array

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