Stoichiometry and microstructure effects on tungsten oxide chemiresistive films

Moulzolf, Scott C.; Ding, Sunan; Lad, Robert J.

doi:10.1016/s0925-4005(01)00757-2

Cited by 147 publications

(91 citation statements)

References 31 publications

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“…than the reported values (10 3 -10 7 Ωcm) for r. f. sputtered WO 3 films [34] It is known that the conductivity of WO 3 films depends on the O 2 /Ar ratio during the sputtering process [34].…”

Section: Electrical Propertiesmentioning

confidence: 65%

Structural, optical, and electrical properties of WOx(Ny) films deposited by reactive dual magnetron sputtering

Mohamed

Anders

2006

Surface and Coatings Technology

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Thin films of tungsten oxynitrides were prepared by dual magnetron sputtering of tungsten using argon/oxygen/nitrogen gas mixtures with various nitrogen/oxygen ratios.The presence of even relatively small amounts of oxygen led to close-to-stoichiometric WO 3 , with little incorporation of nitrogen, therefore the films were labeled as WO x (N y ). Oxygen had a great effect not only on the composition but on the structure of WO x (N y ) films, as shown by Rutherford backscattering and x-ray diffraction, respectively. Significant incorporation of nitrogen occurred only when the nitrogen partial pressure exceeded 89% of the total reactive gas pressure. Sharp changes in the stoichiometry, deposition rate, room temperature resistivity, electrical activation energy and optical band gap were observed when the nitrogen/oxygen ratio was high. The deposition rate increased from 0.31 to 0.89 nm/s, LBNL-59900 1 the room temperature resistivity decreased from 1.65 × 10 8 to 1.82 × 10 -2 Ωcm, the electrical activation energy decreased from 0.97 to 0.067 eV, and the optical band gap decreased from 3.19 to 2.94 eV upon nitrogen incorporation into the films. WO x (N y ) films were highly transparent as long as the nitrogen incorporation was low, and were brownish (absorbing) and partially reflecting as nitrogen incorporation became significant.

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Section: Electrical Propertiesmentioning

confidence: 65%

Structural, optical, and electrical properties of WOx(Ny) films deposited by reactive dual magnetron sputtering

Mohamed

Anders

2006

Surface and Coatings Technology

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“…This is probably due to the presence of WO 2 , the 4f 7/2 peak of which will largely overlap the metal 4f 5/2 peak. There also appears to be some remaining WO 3 . Again, the presence of these reduced forms is likely to be due to reduction by the ion etching beam.…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3] Coatings have been produced by a wide variety of techniques including solgel, [4][5][6] spin-coating, [7] electrochemical deposition, [8] vacuum physical vapour deposition (PVD), [9][10][11][12][13] thermal chemical vapour deposition (CVD) [14,15] and spray pyrolysis. [16][17][18] Solution methods are widely used but can result in film structural and durability constraints.…”

Section: Introductionmentioning

confidence: 99%

Growth of Thin Films of Molybdenum and Tungsten Oxides by Combustion CVD Using Aqueous Precursor Solutions

Davis

Benito

Sheel

et al. 2004

Chemical Vapor Deposition

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Using combustion chemical vapour deposition, layers of molybdenum and tungsten oxides have been deposited on glass and silicon at low temperatures. Inexpensive ammonium salts of molybdate and metatungstate ions were used as precursors and were delivered to the coating flame as an aqueous solution using a nebuliser. The resulting films were analysed by scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), Rutherford backscattering (RBS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).These indicate that the films are continuous, moderately smooth and consist of amorphous, disordered molybdenum and tungsten trioxides.

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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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Stoichiometry and microstructure effects on tungsten oxide chemiresistive films

Cited by 147 publications

References 31 publications

Structural, optical, and electrical properties of WOx(Ny) films deposited by reactive dual magnetron sputtering

Structural, optical, and electrical properties of WOx(Ny) films deposited by reactive dual magnetron sputtering

Growth of Thin Films of Molybdenum and Tungsten Oxides by Combustion CVD Using Aqueous Precursor Solutions

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

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