Sensitivity properties of a novel NO2 gas sensor based on mesoporous WO3 thin film

Teoh, Lay Gaik; Hon, Yi-Ming; Shieh, Jiann; Wei, Lai; Hon, Min–Hsiung

doi:10.1016/s0925-4005(03)00528-8

Cited by 157 publications

(57 citation statements)

References 21 publications

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“…) is an n-type semiconducting metal oxide with a wide band gap that exhibit superior electronic and optical properties [1][2][3][4][5][6][7]. At room temperature, WO 3 usually exists as a mixture of monoclinic () and triclinic () crystal phase structure, and undergoes phase changes to higher symmetries upon heating [8][9][10][11][12].…”

Section: Introduction Tungsten Trioxide (Womentioning

confidence: 99%

Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

Govender

Mwakikunga

Machatine

et al. 2014

Phys. Status Solidi C

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Laser pyrolysis is a synthesis method used to produce thin films and nanomaterials of high quality and purity, by intersecting a laser beam with a chemical precursor. We have chosen laser pyrolysis to synthesize tungsten trioxide starting with tungsten ethoxide precursor. The film had a thickness that varied from 205 nm to 1 µm. Xray diffraction and Raman spectroscopy confirmed the presence of a mixture of hexagonal and tetragonal phase WO 3 in the synthesized film, and it was clear that annealing greatly influenced the phases and types of structures formed. I-V curves of the films showed n-type semiconducting behaviour, but the mixed phase appeared to cause a similar behaviour of dopants in a semiconductor. The refractive index decreased with increasing wavelength and gave values of up to 21 at low wavelengths. The average optical band gap was found to 3.6 eV from UV/Vis spectroscopy. Scanning Electron Microscopy (SEM) showed a mixture of nano-and microstructures and shapes formed after annealing. One of the grown nanostructures was nanorods, this isolated using FIB for possible applications such as an active sensing medium in gas sensors.

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Section: Introduction Tungsten Trioxide (Womentioning

confidence: 99%

Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

Govender

Mwakikunga

Machatine

et al. 2014

Phys. Status Solidi C

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“…Numerous attempts have been made to use various metal-oxide semiconductors as gas sensors [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Among these semiconductors, tungsten trioxide (WO 3 ), an n-type semiconductor, is known as a promising material for sensing NO 2 [1,[5][6][7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Preparation of WO3 nanoparticles and application to NO2 sensor

Meng

Yamazaki

Shen

et al. 2009

Applied Surface Science

108

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“…It may be postulated that Ni-WO 3 can have better response than pure WO 3 due to the extra conduction band electrons of metallic nickel. Hence, the presence of Ni in WO 3 is good for better response in gas-sensing applications (Zhao et al 2000;Teoh et al 2003;Zeng et al 2012). …”

Section: Resultsmentioning

confidence: 99%

“…In the past decade, tungsten-oxide nanostructures (NSs) have been considered as a promising functional material for catalysis and gas-sensing application, because of its photocatalytic, electrochromic, gasochromic and field emission properties (Sawicka et al 2005;Meng et al 2012;Choi and Kim 2009;Serrano et al 2011;Li et al 2001;Liao et al 2006;Luo et al 2009). In WO 3 -based NO 2 gas sensors, the adsorption of NO 2 (oxidizing gases) on the n-type WO 3 modifies the potential barrier between the grain boundaries of WO 3 due to the depletion of charge carriers, leading to a change in electrical conductance (Zhao et al 2000;Teoh et al 2003;Zeng et al 2012). WO 3 nanowires (NWs), nanomesh and nanosheet (NSh) of large surface-tovolume ratio have been studied extensively (Su et al 2011;Zhou et al 2005;Ponzoni et al 2011;Chou et al 2006;Hong et al 2006;Dai et al 2007;Yoo et al 2007;Klinke et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Ni-catalysed WO3 nanostructures grown by electron beam rapid thermal annealing for NO2 gas sensing

et al. 2015

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Ni-catalysed WO 3 (Ni-WO 3 ) nanowires and nanosheets were grown on Si (100) substrates using electron beam evaporation followed by electron beam-assisted rapid thermal annealing process. Gassensing measurements were performed for various concentrations of NO 2 in dry air at a temperature range of 50-400°C. Nanowires and nanosheets show optimum sensor response of 229 and 197 at operating temperatures of 200 and 250°C, respectively, for 100 ppm of NO 2 exposure. Nanowires demonstrated a rapid response time of 66 s, but a slow recovery time of 204 s owing to poor rate of desorption of the adsorbed NO 2 gas molecules from the internal porous structure of nanowires. In contrast, the recovery time for nanosheet was 126 s due to higher desorption rate of the adhered NO 2 molecules associated with low surface area and less porous structure of nanosheet. The gas-sensing mechanism of WO 3 nanostructure is discussed briefly.

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Sensitivity properties of a novel NO2 gas sensor based on mesoporous WO3 thin film

Cited by 157 publications

References 21 publications

Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

Preparation of WO3 nanoparticles and application to NO2 sensor

Ni-catalysed WO3 nanostructures grown by electron beam rapid thermal annealing for NO2 gas sensing

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