1,721,041 research outputs found
Reversed bias Pt/nanostructured ZnO Schottky diode with enhanced electric field for hydrogen sensing
No full textIn this paper, the effect of electric field enhancement on Pt/nanostructured ZnO Schottky diode based hydrogen sensors under reverse bias condition has been investigated. Current–voltage characteristics of these diodes have been studied at temperatures from 25 to 620◦C and their free carrier density con- centration was estimated by exposing the sensors to hydrogen gas. The experimental results show a significantly lower breakdown voltage in reversed bias current–voltage characteristics than the conven- tional Schottky diodes and also greater lateral voltage shift in reverse bias operation than the forward bias. This can be ascribed to the increased localized electric fields emanating from the sharp edges and corners of the nanostructured morphologies. At 620◦C, voltage shifts of 114 and 325mV for 0.06% and 1% hydrogen have been recorded from dynamic response under the reverse bias condition
Pt/SnO2 nanowires/SiC based hydrogen gas sensors
No full textPt/SnO2 nanowires/SiC based metal-oxidesemiconductor\ud
(MOS) devices were fabricated and tested for their gas sensitivity towards hydrogen. Tin oxide (SnO2)\ud
nanowires were grown on SiC substrates by the vapour liquid\ud
solid growth process. The material properties of the SnO2\ud
nanowires such as its formation and dimensions were analyzed\ud
using scanning electron microscopy (SEM). The currentvoltage\ud
(I-V) characteristics at different hydrogen\ud
concentrations are presented. The effective change in the\ud
barrier height for 0.06 and 1% hydrogen were found to be\ud
20.78 and 131.59 meV, respectively. A voltage shift of 310 mV at 530°C for 1% hydrogen was measured
WO3-Au nanocomposite thin films as optical gas sensors
No full textWO3 thin films with peculiar morphology were synthesized coupling sputtering technique and acidic post treatment. Samples were subsequently impregnated with Au nanoparticles and optical gas sensing tests were performed. The films showed good sensitivity towards H2, CO and H2S
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Investigation on the cross sensitivity of NO2 sensors based on In2O3 thin films prepared by sol-gel and vacuum thermal evaporation
No full textIn2O3 thin films have been prepared from commercially available pure In2O3 powders by high vacuum thermal evaporation (HVTE) and from indium iso-propoxide solutions by sol-gel techniques (SG). The films have been deposited on sapphire substrates provided with platinum interdigital sputtered electrodes. The as-deposited HVTE and SG films have been annealed at 500 degrees C for 24 and I h, respectively. The film morphology, crystalline phase and chemical composition have been characterised by SEM, glancing angle XRD and XPS techniques. After annealing at 500 degrees C the films' microstructure turns from amorphous to crystalline with the development of highly crystalline cubic In2O3-x (JCPDS card 6-0416). XPS characterisation has revealed the formation of stoichiometric In2O3 (HVTE) and nearly stoichiometric In2O3-x (SG) after annealing. SEM characterisation has highlighted substantial morphological differences between the SG (highly porous microstructure) and HVTE (denser) films. All the films show the highest sensitivity to NO2 gas (0.7-7 ppm concentration range), at 250 degrees C working temperature. At this temperature and 0.7 ppm NO2 the calculated sensitivities (S = R-g/R-a) yield S = 10 and S = 7 for SG and HVTE, respectively. No cross sensitivity have been found by exposing the In2O3 films to CO and CH4. Negligible H2O cross has resulted in the 40-80% relative humidity range, as well as to I ppm Cl-2 and 10 ppm NO. Only 1000 ppm C2H5OH has resulted to have a significant cross to the NO2 response. (C) 1999 Published by Elsevier Science Ltd. All rights reserved
Polycrystalline and amorphous sol-gel derived WO3 thin films and their gas sensing properties
No full textLayered WO3/ZnO/36 degrees LiTaO(3)SAW gas sensor sensitive towards ethanol vapour and humidity
No full textEthanol sensing in dry and humid air by layered surface acoustic wave (SAW) devices is presented. The transducing platform is based on 36 degrees YX LiTaO3 layered SAW device, utilising a 1.2 mu m zinc oxide (ZnO) intermediate layer and 150 nm tungsten trioxide (WO3) sensing layer. Sheet conductivity calculations show that maximum sensitivity is achieved for ZnO layer thickness between I and 1.5 mu m. Sensor performance was analyzed in terms of response magnitude as a function of operational temperature and different relative humidity (RH). Frequency shifts of 119, 90 and 86 kHz towards 500 ppm of ethanol in synthetic air were observed for 0, 25 and 50% RH, respectively. All RH levels were measured at 20 degrees C. At an operating temperature of 300 degrees C, the largest response towards 500 ppm of ethanol was observed. Response magnitude was found to decrease with increasing RH and decreasing operating temperature. Furthermore, the effect of elevated temperatures on the sensors surface morphology is characterised by AYM and SEM techniques. It is suggested that the morphological modifications, due to elevated temperatures play an important role in the sensing behaviour of the WO3 films. (c) 2006 Elsevier B.V. All rights reserved
Titanium Dioxide-Based 64° YX LiNbO3 SurfaceAcoustic Wave Hydrogen Gas Sensors
Full text linkAmorphous titanium dioxide (TiO2) and gold (Au) doped TiO2-based surface acoustic wave (SAW) sensors have been investigated
as hydrogen gas detectors. The nanocrystal-doped TiO2 films were synthesized through a sol-gel route,mixing a Ti-butoxide-based
solution with diluted colloidal gold nanoparticles. The films were deposited via spin coating onto 64° YX LiNbO3 SAWtransducers
in a helium atmosphere. The SAW gas sensors were operated at various temperatures between 150 and 310 °C. It was found that
gold doping on TiO2 increased the device sensitivity and reduced the optimum operating temperature
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