Phase transformations in WO3 thin films during annealing

Mohammad, Ahmad Al; Gillet, M.

doi:10.1016/s0040-6090(02)00090-1

Cited by 121 publications

(78 citation statements)

References 28 publications

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“…The WO 3 phase had characteristic peaks attributable to monoclinic WO 3 . The observation is in accord with earlier reports [53,54]. The diffraction peaks in the WO 3 -modified PtRh/Vulcan nanoparticles (Fig.…”

Section: Resultssupporting

confidence: 93%

Enhancement of activity of PtRh nanoparticles towards oxidation of ethanol through modification with molybdenum oxide or tungsten oxide

Miecznikowski

2012

J Solid State Electrochem

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Electrocatalytic systems utilizing carbon (Vulcan)-supported PtRh nanoparticles (PtRh/Vulcan) admixed with either molybdenum oxide or tungsten oxide were tested and compared during electrooxidation of ethanol. The systems' performance was diagnosed using electrochemical techniques such as voltammetry and chronoamperometry. The proposed electrocatalytic materials were also characterized with X-ray diffraction (XRD), transmission and scanning electron microscopies (TEM and SEM), as well as SEM-coupled energy dispersive X-ray spectroscopy (SEM-EDX). For both systems containing molybdenum and tungsten oxides, enhancements in catalytic activities (relative to the behavior observed at bare PtRh/Vulcan nanoparticles) were found during ethanol electrooxidation at room temperature (22°C). Further, it was from chronoamperometric current (density)-time responses that anodic electrocatalytic currents measured at 0.3 V (vs. RHE) were more than 20% higher in the case of the MoO 3 -containing PtRh/Vulcan system relative to that utilizing WO 3 . The diagnostic "CO-stripping" experiments were consistent with the view that addition of molybdenum oxide or tungsten oxide to PtRh/Vulcan tended to shift potential for the oxidation of inhibiting CO-adsorbate ca. 80 or 40 mV towards less negative values in comparison to the analogous but oxide-free system. The fact that carbon (Vulcan)-supported PtRu nanoparticles exhibited higher electrocatalytic reactivity observed phenomena may be attributed to specific interactions between noble metal centers and the oxides in addition to chemical reactivity of metal oxo groups in the vicinity of PtRh/ Vulcan at the electrocatalytic interface.

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Section: Resultssupporting

confidence: 93%

Enhancement of activity of PtRh nanoparticles towards oxidation of ethanol through modification with molybdenum oxide or tungsten oxide

Miecznikowski

2012

J Solid State Electrochem

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“…The WO 3-x structures in this study are crystalline after deposition, since the temperature of the substrate during deposition exceeds the crystallization temperature of WO 3-x of 350-390 8C. [21,25,26] As their EDS signals indicate, both the closed crystallite and nanogranular thin films are not fully reduced after 30 min of reduction. It was observed, however, that a reduction treatment of 60 min is sufficient for complete reduction of these relatively thick films.…”

Section: Effects Of the Reduction Process On The Composition And Crysmentioning

confidence: 76%

Metallic Tungsten Nanostructures and Highly Nanostructured Thin Films by Deposition of Tungsten Oxide and Subsequent Reduction in a Single Hot‐Wire CVD Process

Harks

Houweling

Jong

et al. 2012

Chemical Vapor Deposition

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The synthesis of metallic tungsten nanostructures and highly nanostructured thin films is presented. Crystalline tungsten oxide nanostructures are deposited on glassy carbon substrates kept at 700 AE 100 8C by oxidizing resistively heated tungsten filaments in an air flow under subatmospheric pressures. The internal morphology of the deposited tungsten oxide can be reproducibly controlled by the air pressure. After deposition, the tungsten oxides have been fully reduced to metallic tungsten by atomic hydrogen at a temperature of about 730 8C. Polycrystalline metallic tungsten nanofibers, nanocrystallites, closed crystallite films, and nanogranular films are thus obtained in a single procedure involving deposition and subsequent reduction, at relatively low temperatures.

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“…Thin films consisting of WO 3 are amorphous when deposited at a temperature below 350 8C with radio frequency (RF) magnetron sputtering, [8,15] RF reactive sputtering, [14] and thermal evaporation, [22] while annealing above 350-390 8C induces crystallization into a monoclinic phase. [8,14,15,22,48] Ozkan et al studied the crystallization of evaporated amorphous WO 3 films and found that annealing at temperatures above 390 8C for 1 h in air yields completely crystalline films.…”

Section: Raman Spectroscopymentioning

confidence: 99%

“…[8,14,15,22,48] Ozkan et al studied the crystallization of evaporated amorphous WO 3 films and found that annealing at temperatures above 390 8C for 1 h in air yields completely crystalline films. [48] In order to determine the crystal phase(s) of the films we investigated, XRD and Raman measurements were performed.…”

Section: Raman Spectroscopymentioning

confidence: 99%

“…It is used in, e.g., optical displays, [3] smart windows, [1,2,5] gas/chemical sensors, [8][9][10][14][15][16] and solar cells. [6] There is a wide spectrum of deposition techniques that are used to produce WO 3 thin films, such as spray-pyrolysis deposition, [17][18][19] spin-coating [16,20] or dropcasting of solutions, [21] magnetron sputtering, [8,15] reactive sputtering, [14] thermal evaporation, [22] and the oxidation of W films. [20,[23][24][25] Aerosol assisted (AA) CVD, [26,27] atmospheric pressure (AP) CVD, [26,[28][29][30][31][32] low pressure (LP) CVD [33,34] , metal-organic (MO) CVD, [35,36] and hotwire (HW) CVD [37][38][39][40][41][42][43] techniques have recently also been proven to be versatile methods to produce various metal oxide nanostructures.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of WO₃ Nanogranular Thin Films by Hot‐Wire CVD

Houweling

Geus

Schropp

2010

Chemical Vapor Deposition

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By resistively heating tungsten filaments in a constant air flow under a reduced pressure, nanogranular amorphous WO 3 thin films are deposited on glassy carbon substrates. The substrate surface temperature is monitored by a thermocouple. For deposition times of 15 min and longer, the films show crystallization into a monoclinic nanocrystalline WO 3 phase due to thermal radiation from the filaments. The thin films thus deposited consist of very small grains with sizes of 8-16 nm for a film deposited in 5 min, and to sizes of 20-42 nm for a film deposited in 60 min. By heating the bottom of the substrate to 950 8C, the grains sinter to nanorods with diameters of 146 AE 26 nm with lengths of up to 750 nm. The morphology, the film thickness, the grain and the nanorod sizes of the depositions are characterized by high-resolution scanning electron microscopy (HRSEM), and the atomic species present in the films by energy-dispersive X-ray spectroscopy (EDS). The number of atoms in the films is determined by Rutherford backscattering spectrometry (RBS). The results are combined with measurements of the physical thicknesses, and thus the mass densities of the deposited films are obtained. X-ray diffraction (XRD) and Raman spectroscopy are used to characterize the deposited films crystallographically and chemically, respectively.

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Phase transformations in WO3 thin films during annealing

Cited by 121 publications

References 28 publications

Enhancement of activity of PtRh nanoparticles towards oxidation of ethanol through modification with molybdenum oxide or tungsten oxide

Enhancement of activity of PtRh nanoparticles towards oxidation of ethanol through modification with molybdenum oxide or tungsten oxide

Metallic Tungsten Nanostructures and Highly Nanostructured Thin Films by Deposition of Tungsten Oxide and Subsequent Reduction in a Single Hot‐Wire CVD Process

Synthesis of WO₃ Nanogranular Thin Films by Hot‐Wire CVD

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Phase transformations in WO3 thin films during annealing

Cited by 121 publications

References 28 publications

Enhancement of activity of PtRh nanoparticles towards oxidation of ethanol through modification with molybdenum oxide or tungsten oxide

Enhancement of activity of PtRh nanoparticles towards oxidation of ethanol through modification with molybdenum oxide or tungsten oxide

Metallic Tungsten Nanostructures and Highly Nanostructured Thin Films by Deposition of Tungsten Oxide and Subsequent Reduction in a Single Hot‐Wire CVD Process

Synthesis of WO3 Nanogranular Thin Films by Hot‐Wire CVD

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Synthesis of WO₃ Nanogranular Thin Films by Hot‐Wire CVD