Operating temperature effect in WO&lt;inf&gt;3&lt;/inf&gt; films for gas sensing

Govender, Malcolm; Motaung, David E.; Mwakikunga, Bonex W.; Umapathy, Siva; Sil, Shreekantha; Prasad, Arun K.; Machatine, Augusto Gonçalo Jose; Kunert, H.W.

doi:10.1109/icsens.2013.6688192

Cited by 6 publications

(5 citation statements)

References 20 publications

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“…The quantity τ 1 and τ 2 are the time constants for response and recovery steps, these parameters were calculated by fitting the first order exponential function in equations ( 11) and (12). Figure 11(a) shows a response profile which was calculated from equation (11). The pattern shows better adsorption for all concentrations of the NH 3 gas at 25 °C compared to the one at 100 °C.…”

Section: Comparison Of In Situ Raman Spectroscopy-gas-sensor Tester A...mentioning

confidence: 99%

“…The pattern shows better adsorption for all concentrations of the NH 3 gas at 25 °C compared to the one at 100 °C. A respose time constant plot was extracted from the same equation (11) as shown in figure 11(b). The response time constant in this paper is defined as the time it takes the sensor to reach 63% i.e 1 -e −1 of its maximum after exposed to the gas [15,38,39].…”

Section: Comparison Of In Situ Raman Spectroscopy-gas-sensor Tester A...mentioning

confidence: 99%

“…This enhancement is observed to be absent when the material is exposed to air. The effect is reported to be reversible and the band is attributed to Cu 2 S vibration, thus showing reactivity of Cu doped SnO 2 with H 2 S. Nanocrystalline WO 3 powder has also been found to react with the reducing gases CH 4 and CO resulting in the growth of two broad band peaks at 1300 cm −1 and 1600 cm −1 which were observed to be absent in the Raman spectrum of pure WO 3 [10,11]. Whereas, these peaks disappeared in the presence of an oxidizing gas NO 2 and thereby are attributed to the graphitic carbon peak usually present in many carbon materials [7].…”

Section: Introductionmentioning

confidence: 99%

“…Raman spectroscopy is a reliable, sensitive and nondestructive method used in characterizing metal oxides and other nanomaterials [7,8]. The Raman technique has been applied to study adsorption of molecules on the surface of metal oxides and to monitor their selective ability toward certain species of gas [9][10][11]. Among these studies, A 1g mode of SnO 2 was observed to show a huge enhancement when H 2 S gas reacted with Cu doped SnO 2 nanomaterial [9].…”

Section: Introductionmentioning

confidence: 99%

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Blue- and red-shifts of V₂O₅phonons in NH₃environment byin situRaman spectroscopy

Akande

Machatine

Masina

et al. 2017

J. Phys. D: Appl. Phys.

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A layer of ~30 nm V2O5/100 nm-SiO2 on Si was employed in the in situ Raman spectroscopy in the presence of NH3 effluent from a thermal decomposition of ammonium acetate salt with the salt heated at 100 °C. When the layer is placed at 25 °C, we observe a reversible red-shift of 194 cm−1 V2O5 phonon by 2 cm−1 upon NH3 gas injection to saturation, as well as a reversible blue-shift of the 996 cm−1 by 4 cm−1 upon NH3 injection. However when the sensing layer is placed at 100 °C, the 194 cm−1 remains un-shifted while the 996 cm−1 phonon is red-shifted. There is a decrease/increase in intensity of the 145 cm−1 phonon at 25 °C/100 °C when NH3 interacts with V2O5 surface. Using the traditional and quantitative gas sensor tester system, we find that the V2O5 sensor at 25 °C responds faster than at 100 °C up to 20 ppm of NH3 beyond which it responds faster at 100 °C than at 25 °C. Overall rankings of the NH3 gas sensing features between the two techniques showed that the in situ Raman spectroscopy is faster in response compared with the traditional chemi-resistive tester. Hooke’s law, phonon confinement in ~51 nm globular particles with ~20 nm pore size and physisorption/chemisorption principles have been employed in the explanation of the data presented.

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Section: Comparison Of In Situ Raman Spectroscopy-gas-sensor Tester A...mentioning

confidence: 99%

Section: Comparison Of In Situ Raman Spectroscopy-gas-sensor Tester A...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Blue- and red-shifts of V₂O₅phonons in NH₃environment byin situRaman spectroscopy

Akande

Machatine

Masina

et al. 2017

J. Phys. D: Appl. Phys.

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“…It is well known that tungsten trioxide (WO 3 ), amongst other semiconducting metal oxides (SMOs), offers the best resistive-type sensing of highly toxic nitrogen dioxide (NO 2 ) gas [1,2]. However, WO 3 also shows good sensing towards reducing gases such as H 2 S, NH 3 , acetone and ethanol, which negatively impacts selectivity [3].…”

Section: Introductionmentioning

confidence: 99%

Selective room-temperature sensing of NO<inf>2</inf> by WO<inf>3</inf> film/graphene layers

Govender

Mwakikunga

Mathur

et al. 2014

IEEE SENSORS 2014 Proceedings

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This is one of the first attempts of making WO 3 thick film selective at low operating temperature by placing graphene sheets directly on the film surface. The WO 3 film was prepared by DC magnetron reactive sputtering of a pure tungsten target and annealing in air. The thickness of the film averaged 507 nm from FIB cross-sectioning and STEM measurement. The film was characterized with XRD, XPS and Raman spectroscopy. Graphene was synthesized on copper foil using plasma enhanced chemical vapor deposition of methane gas, which was found to produce three monolayers of graphene sheets according to Raman spectroscopic analysis. The graphene was transferred onto the WO 3 film and annealed. It was found that the pure WO 3 sensed low concentrations of nitrogen dioxide at 30 o C and 100 o C operating temperature. The selectivity towards nitrogen dioxide over ammonia and carbon monoxide was achieved with graphene on the tungsten trioxide film at the compromise of sensitivity at both operating temperatures. The analysis of the graphene/WO 3 composite orientation may lead to improved sensor capabilities as well as better understanding of the sensing mechanism.

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MEMS based tin oxide thin film gas sensor for diabetes mellitus applications

Sachdeva

Agarwal

2018

Microsyst Technol

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Operating temperature effect in WO<inf>3</inf> films for gas sensing

Cited by 6 publications

References 20 publications

Blue- and red-shifts of V₂O₅phonons in NH₃environment byin situRaman spectroscopy

Blue- and red-shifts of V₂O₅phonons in NH₃environment byin situRaman spectroscopy

Selective room-temperature sensing of NO<inf>2</inf> by WO<inf>3</inf> film/graphene layers

MEMS based tin oxide thin film gas sensor for diabetes mellitus applications

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Operating temperature effect in WO<inf>3</inf> films for gas sensing

Cited by 6 publications

References 20 publications

Blue- and red-shifts of V2O5phonons in NH3environment byin situRaman spectroscopy

Blue- and red-shifts of V2O5phonons in NH3environment byin situRaman spectroscopy

Selective room-temperature sensing of NO<inf>2</inf> by WO<inf>3</inf> film/graphene layers

MEMS based tin oxide thin film gas sensor for diabetes mellitus applications

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Product

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Blue- and red-shifts of V₂O₅phonons in NH₃environment byin situRaman spectroscopy

Blue- and red-shifts of V₂O₅phonons in NH₃environment byin situRaman spectroscopy