Effect of Pt Nanoparticles on the Optical Gas Sensing Properties of WO3 Thin Films (original) (raw)
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WO 3 thin films for optical gas sensing
2011
Thin films of WO 3 were deposited on quartz substrates by the RF magnetron sputtering. Different annealing temperatures of 423, 473, 573 and 773 K were used for different films. The films were annealed under the ambient conditions. The influence of the annealing temperature on the structure and optical properties of the WO 3 was studied. The surface morphology of the thin films was investigated by atomic force microscopy, which showed that the annealing temperature increases the surface crystallinity. Spectrometric measurements of transmittance were carried out in the wavelength range 190-3300 nm and the energy gap, E g , has been evaluated.
Gas sensing properties of WO3 thin films deposited by rf sputtering
Sensors and Actuators B: Chemical, 2007
WO 3 thin films were deposited by reactive radio frequency (rf) sputtering from a pure tungsten target. The deposition process was conducted with three interruptions and the interruption time was 30, 90 and 300 s. On the basis of these films, sensing layers were prepared and their responses to NO 2 , ammonia and ethanol were investigated. It was found that the sensing layers prepared with an interruption time of more than 90 s showed the best sensing properties.
NO2 Sensing Properties of WO3 Thin Films Deposited by Rf-Magnetron Sputtering
Conference Papers in Science, 2014
Tungsten trioxide (WO3) thin films were deposited by Rf-magnetron sputtering onto Pt interdigital electrodes fabricated on corning glass substrates. NO2gas sensing properties of the prepared WO3thin films were investigated by incorporation of catalysts (Sn, Zn, and Pt) in the form of nanoclusters. The structural and optical properties of the deposited WO3thin films have been studied by X-ray diffraction (XRD) and UV-Visible spectroscopy, respectively. The gas sensing characteristics of all the prepared sensor structures were studied towards 5 ppm of NO2gas. The maximum sensing response of about 238 was observed for WO3film having Sn catalyst at a comparatively lower operating temperature of 200°C. The possible sensing mechanism has been highlighted to support the obtained results.
Structural and optical characterization of WO3 thin films for gas sensor applications
Journal of Applied Physics, 2005
The structural and optical properties of WO 3 nanorods prepared by oblique angle depositions were studied and compared with WO 3 thin films. The x-ray diffraction analysis revealed that both the thin films and nanorods annealed at temperatures of 400 and 500°C had an orthorhombic structure, while only the thin films showed a monoclinic phase when annealed at 300°C. The band gap energies of the thin films and nanorods all decreased with increasing annealing temperature. The polarized optical absorbance spectra of the as-deposited nanorod samples initially showed anisotropy, but after annealing at temperatures above 400°C, they became isotropic. This is believed to result from the changes in morphology, crystal structure, and orientation of the nanorod arrays after annealing.
Enhanced sensing properties of WO3 and its binary systems for thin films gas sensors
Journal of Physics: Conference Series
Thin films of pure WO3 and the binary systems of TiO2:WO3,MoO3:WO3,Cr2O3:WO3, and SnO2:WO3 were prepared by pulsed laser deposition method. The single and binary compounds were sintered at 1273K for five hours. The deposition were done under vacuum of 2x10-2 Torr at various substrates like glass and single crystal silicon wafer with negative conductance at ambient temperature thickness of ≍150 nm. The structures and morphology of pure WO3 and the binary systems TiO2:WO3,MoO3:WO3,Cr2O3:WO3, and SnO2:WO3 compounds and the deposited thin films were studied by X–ray diffraction and AFM atomic force microscope. The optical properties imply optical energy gap as well as optical constants for all the single and binary system were determined and discussed. The results of gas sensing measurements to NO2 gas showed that MoO3:WO3 sensors prepared on n- Si substrate showed maximum sensitivity (194.5%) at operating temperature 300K.
Japanese Journal of Applied Physics, 2006
Tungsten trioxide (WO 3) thin films gas sensors were prepared by the KrF excimer pulsed laser deposition (PLD) method. The films were prepared on the quartz glass, silicon and also on the Al 2 O 3 sensor substrates with platinum interdigitated electrodes. The effect of doping of the platinum (Pt), palladium (Pd) or gold (Au) on the WO 3 thin film was also investigated. These metals were doped to the WO 3 thin film by the DC sputtering process during the PLD. The substrate temperature and the oxygen pressure were 400 C and 100 mTorr, respectively, during the deposition. The films were characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). The sensitivity of the prepared sensors to 60 ppm NO gas was examined using the two terminal resistance method in a chamber at atmospheric pressure and operating temperatures of 25-350 C. The sensitivity of the WO 3 thin films doped with Pt, Pd, or Au was found to be higher than that of the undoped WO 3 thin film.
Structural, Optical and Gas Sensing Properties of Tungsten Trioxide Thin Films and Nanoparticles
Tungsten trioxide (WO 3) thin films were deposited on silica, silicon and alumina substrates and their crystal structure, surface morphology, optical and gas-sensing properties were compared with those of WO 3 nanoparticles. As deposited films were amorphous and crystallized into the mon-oclinic phase with heat treatment. Raman spectroscopy revealed that the short-range structure of amorphous, crystalline films and nanoparticles of WO 3 are similar, but the amorphous phase contain W 6+ = O terminal bonds that do not exist in bulk and nanocrystalline samples. Raman studies confirmed that amorphous samples contain higher concentration of hydrogen and hydroxyl ion impurities, which affect the optical bandgap. Thin films show a response of 3 for 150 ppm of H 2 S and 7 for 2000 ppm of C 2 H 5 OH. Platelet shaped nanoparticles exhibit higher response of 37 and fast response and recovery times of 1 to 2 min for 150 ppm of H 2 S.
Development of Nano- \hbox {WO}_{3}$$ WO 3 Doped with NiO for Wireless Gas Sensors
Arabian Journal for Science and Engineering, 2018
WO 3 doped with NiO nanopowders with different NiO concentrations were prepared by sol-gel technique. The fabrication of the thin films for gas sensors applications was utilized using thermal vacuum evaporation technique. The morphological structure, crystallinity and optical properties of WO 3 and NiO-doped WO 3 nanopowders were characterized using scanning electron microscopy, X-ray diffraction and UV-Vis spectrophotometer, respectively. The electrical behaviors of the sensors were determined and measured by the two platinum electrodes sensor's resistance with different gases at various temperatures. The results show that a great response to CO 2 gas was 164% at 5% doping ratio which is applicable for all environmental and industrial fields. GSM module by MAX circuit was applied on gas sensor devices to send a wireless message telling that there is a leakage in the area which the sensor installed. Keywords WO 3 • WO 3 −NiO • Thin films • Sputtering • CO 2 gas sensor • Wireless 1 Introduction Wireless gas sensor is an excellent technique to monitor and control the environment remotely that makes it easy to detect any emissions of different toxic gases such as CO 2 , O 2 , NO, CO, C 6 H 4 , NH 3 , CH 4 and LPG from different sources in industry which has been polluting our air without any intensive observation. Moreover it is used for the explosives detection, environmental monitoring, industrial process control and automotive applications. As a result, it is an urgent
Proceedings IMCS 2012
Tungsten trioxide films with nanocrystalline surface were manufactured by deposition of a three layer WO 3 /W/WO 3 structure by RF sputtering and successive annealing of the structure in appropriate temperature range. Surface morphology was controlled by the thickness of the metal layer and upper oxide layer. WO 3 sample after annealing was not homogeneous, revealing lower density in the region of upper layer. The obtained samples were sensitive to nitrogen dioxide, exhibiting better stability at lower working temperatures.
Characterization of PLD grown WO 3 thin films for gas sensing
Applied Surface Science, 2017
Tungsten trioxide (WO 3) thin films were grown by pulsed laser deposition (PLD) with the aim to be applied in gas sensors. The films were studied by atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and profilometry. To study the gas sensing behavior of these WO 3 films, they were deposited on quartz resonators and the quartz crystal microbalance (QCM) method was applied to analyze their gas sensitivity. Synthesis of tetragonal-WO 3 films starting from a target with predominantly monoclinic WO 3 phase was observed. The films deposited at 300 °C presented a surface topology favorable for the sorption properties, consisting of a film matrix with protruding craters/cavities. QCM prototype sensors with such films were tested for NO 2 sensing. The PLD grown WO 3 thin films show good sensitivity and fast reaction at-3/20-room temperature, even in as-deposited state. With the presented technology, the manufacturing of QCM gas sensors is simple, fast and cost-effective, and it is also suitable for energy-effective portable equipment for on-line monitoring of environmental changes.