Detection and characterization of CO gas using LTCC micro-hotplates (original) (raw)
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Fabrication of CO Gas Sensor Device Based Indium Tin Oxide ( ITO ) By Thin Film Technology
2015
In this paper it will be described the design and fabrication of microdevice to be used as platform for CO (Carbon monoxide) gas sensor based on indium tin oxide (ITO). The device has been designed on silicon substrate with an active area of 3x3 mm 2 , and consisted of bonding pad, heater, electrode, and temperature sensor components. The minimum feature size used is 50 microns, as allowed by the capability of photolithographic process. The formation of microdevice structure has been done mainly using lift-off technique on platinum (Pt) layer, which was deposited by DC sputtering with aluminium (Al) as sacrificial layer. The overall chip dimension is not more than 5x5 mm 2 .The measurement conducted to study the resistance versus temperature characteristics has shown that the heater and temperature sensor elements have functioned as expected, in which their resistances change linearly with an increase in substrate temperature between 20-200 0 C. The range of increase in resistance values for the heater is 500-1000 ohm, whereas for the temperature sensor is 100-300 ohm.
Microsensor based on low temperature cofired ceramics and gas-sensitive thin film
Thin Solid Films, 2003
A novel design of gas sensor using low temperature cofired ceramics (LTCC) and thin film technologies is presented. The LTCC structure is composed essentially of two ceramic layers with interlayer thick film Pt heater, interdigitated electrodes on top, contact pads and metallic connections realised by vias. The thin films of both SnO2 and In2O3, intentionally doped and activated, were deposited
Sensors and Actuators B: Chemical, 2001
We report on the design, implementation and characterisation of a thick-®lm gas sensor deposited for the ®rst time by screen-printing technique onto a micromachined hotplate, the microheater maintains a ®lm temperature as high as 4008C with <30 mW of input power. The microheater consists of a dielectric stacked membrane equipped with embedded polysilicon resistors acting as heating element as well as temperature sensing elements. Extensive ®nite-element computer simulations were carried out during the design step to optimise the radial temperature gradient up to 12008C/mm. A newly developed scheme for temperature measurement was adopted for on-line adjustment of the ®lm temperature through a conventional low-power proportional integral (PI) regulator. Deposition of sensing layers based on semiconductor oxides, such as SnO 2 was achieved by computer-aided screen-printing. The ®lms were then ®red through the microheater itself to guarantee thermodynamic stability for long time exploitation. The response of the device to CO, CH 4 and NO 2 at concentrations typical for indoor and outdoor applications was recorded by measuring the ®lm resistance through ultra high impedance CMOS circuit.
Sensors and Actuators B: Chemical, 2008
Ultrathin tin oxide films were deposited on flat hotplate templates using atomic layer deposition (ALD) techniques with SnCl 4 and H 2 O 2 as the reactants. The resistance of the SnO x ALD films across an electrode gap on the hotplate template was observed to oscillate and decrease versus the number of sequential SnCl 4 and H 2 O 2 reactions at 250 • C. The resistance also varied with exposure to O 2 and CO pressure at 300 • C and 325 • C. A wide range of SnO x ALD film thicknesses between 15.9 Å and 58.7 Å was prepared by varying the number of sequential, self-limiting SnCl 4 and H 2 O 2 reactions. The CO gas sensor response was then measured for these SnO x ALD film thicknesses at 300 • C. The CO gas sensor response increased for increasing thicknesses between 15.9 Å and 26.2 Å and decreased for increasing thicknesses between 26.2 Å and 58.7 Å. The results were interpreted in terms of the Debye length and resistance for the SnO x ALD films. The Debye length is comparable with the SnO x ALD film thickness of 26.2 Å corresponding to the maximum responsivity for CO gas sensing. For film thicknesses >26.2 Å, the responsivity decrease was explained by a larger fraction of the film with thickness greater than the Debye length that is not affected by the O 2 and CO chemisorption. For film thicknesses <26.2 Å, the responsivity decrease was attributed to the increasing resistance of the SnO x ALD film. The gas sensor response was temperature dependent and displayed its highest responsivity at temperatures between 250 • C and 325 • C. The response times of the SnO x ALD gas sensors were also faster at the higher temperatures >260 • C.
Tin Dioxide -CNT Based Gas Sensor Design
International Journal of Emerging Technology and Advanced Engineering, 2020
The SnO 2-CNT based gas sensors can detect harmful gases and also measure their toxic effects on environment as well as living creatures. Monitoring of the sensitivity of the hazardous gases (CO) and volatile organic compound (Acetone) by our SnO 2-CNT based gas sensor are the main goal here. Cross sensitivity of SnO 2-CNT based gas sensor over volatile organic compound (ethyl alcohol) and combustible gases (methane) are also observed here. Keywords-SnO 2-CNT gas sensors, sensitivity of gas sensors, capacitive effect, Scanning Electron Microscopy (SEM), High energy Sonicator, substrate coating and X-ray diffraction (XRD).
CO and CO2 thin-film SnO2 gas sensors on Si substrates
Sensors and Actuators B-chemical, 1994
Thm-fun SnOz gas sensors have been structured on B substrates The sensors are temperature stable at 900 "C m synthetic air for 48 h No s@kant outdnTwon of the sensor layers can be observed after anneahng Pt catalysts lead to CO sensors wthout cross sensltnnty to CO, Pt/Ca catalyst combinations also lead to CO? gas response CO, sensltwlty between loo0 and 10000 ppm has been demonstrated at 270 "C CO2 rnqht be mchrectly detected wa hunwhty exchange between CO, and the heated Ca-catalysed SnO, surface &word Carbon dmxlde, Carbon monoxide, Gas sensors, Sd~con, Tm oxide
Nanostructured SnO2–ZnO composite gas sensors for selective detection of carbon monoxide
Beilstein Journal of Nanotechnology, 2016
A series of SnO2–ZnO composite nanostructured (thin) films with different amounts of SnO2 (from 0 to 50 wt %) was prepared and deposited on a miniaturized porous alumina transducer using the sol–gel and dip coating method. The transducer, developed by our research group, contains Au interdigital electrodes on one side and a Pt heater on the other side. The sensing films were characterized using SEM and AFM techniques. Highly toxic and flammable gases (CO, CO2, CH4, and C3H8) were tested under lab conditions (carrier gas was dry air) using a special gas sensing cell developed by our research group. The gas concentrations varied between 5 and 2000 ppm and the optimum working temperatures were in the range of 210–300 °C. It was found that the sensing performance was influenced by the amount of oxide components present in the composite material. Improved sensing performance was achieved for the ZnO (98 wt %)–SnO2 (2 wt %) composite as compared to the sensors containing only the pristine...
Sensors and Actuators B: Chemical, 1994
Indmm bn oxtde (ITO) polycrystalhoe thm films grown on alumma substrates by thermal evaporation, followed by annealing m a humld envnonment, are used for fabncatmg a gas sensor to detect carbon duxude (CO,) gas produced by incomplete burning m domestlc combustion equipment and combustion processes IT0 thm-6lm gas sensors with a thrckness of about 150 nm show a maxunum senatlvlty when operated at a temperature of 573 K for vanous concentrations of CO2 gas A tentatlve mechamsm based on molecular orbIta (MO) theory IS proposed for the role of CO2 gas m mcreasmg the conductance of IT0 thm-film gas sensors This increase m conductance IS utdlzed to mltlate the tnggenng of an electromc alarm system ~&WV& IT0 thm films, Carbon dmxlde gas sensor
Sensors, 2012
Thin films of tin oxide mixed cerium oxide were grown on unheated substrates by physical vapor deposition. The films were annealed in air at 500 °C for two hours, and were characterized using X-ray photoelectron spectroscopy, atomic force microscopy and optical spectrophotometry. X-ray photoelectron spectroscopy and atomic force microscopy results reveal that the films were highly porous and porosity of our films was found to be in the range of 11.6-21.7%. The films were investigated for the detection of carbon monoxide, and were found to be highly sensitive. We found that 430 °C was the optimum operating temperature for sensing CO gas at concentrations as low as 5 ppm. Our sensors exhibited fast response and recovery times of 26 s and 30 s, respectively.
Properties of reactively sputtered tin oxide films as CO gas sensors
Sensors and Actuators B: Chemical, 1995
SnO2 thin films for CO sensor applications have been obtained by r.L reactive sputtering from a target of the same compound in an Ar--O2 atmosphere. The films are polycrystalline with mean grain sizes in the range 6(I-100 nm. An energy gap of about 4.14 eV is determined from the analysis of the spectral dependence of the absorption coefficient. The electrical measurements are carried out in a flowing gas system where dry air at ambient pressure is used as the carrier and reference gas. The CO sensitivity is found to be dependent on the sputtering conditions. The samples with relatively high initial resistance (> 2 klI) are sensitive to CO injection. The film sensitivity is found to reach the highest values in the temperature range 500-600 K. Keywords: Carbon monoxide sensor; Tin oxide 0925-4005/95/$09.50 © 1995 Elsevier Science S.A. All rights reserved SSDI 0925-4005 (94)01275-M