• Journal of Sensor Science and Technology
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• v.15 no.1
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• pp.13-19
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• 2006

The micro-gas sensor based on carbon nanotubes (CNTs) was fabricated and its gas sensing characteristics on nitrogen dioxide ($NO_{2}$) have been investigated. The sensor consists of a heater, an insulating layer, a pair of contact electrodes, and CNT-sensing film on a micromachined diaphragm. The heater plays a role in the temperature change to modify sensor operation. Gas sensor responses of CNT-film to $NO_{2}$ at room temperature are reported. The sensor exhibits a reversible response with a time constant of a few minutes at thermal treatment temperature of $130^{\circ}C$.

• Korean Journal of Materials Research
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• v.25 no.7
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• pp.358-363
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• 2015

We present an excellent detection for nitrogen monoxide (NO) gas using polycrystalline ZnO wire-like films synthesized via a simple method combined with sputtering of Zn metallic films and subsequent thermal oxidation of the sputtered Zn nanowire films in dry air. Structural and morphological characterization revealed that it would be possible to synthesize polycrystalline hexagonal wurtzite ZnO films of a wire-like nanostructure with widths of 100-150 nm and lengths of several microns by controlling the sputtering conditions. It was found from the gas sensing measurements that the ZnO wire-like thin film gas sensor showed a significantly high response, with a maximum value of 29.2 for 2 ppm NO at $200^{\circ}C$, as well as a reversible fast response to NO with a very low detection limit of 50 ppb. In addition, the ZnO wire-like thin film gas sensor also displayed an NO-selective sensing response for NO, $O_2$, $H_2$, $NH_3$, and CO gases. Our results illustrate that polycrystalline ZnO wire-like thin films are potential sensing materials for the fabrication of NO-sensitive high-performance gas sensors.

• Journal of Sensor Science and Technology
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• v.29 no.1
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• pp.14-18
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• 2020

This study investigates the nitrogen dioxide (NO₂) sensing characteristics of an Si MOSFET gas sensor with a tungsten trioxide (WO₃) sensing layer deposited using the sputtering method. The Si MOSFET gas sensor consists of a horizontal floating gate (FG) interdigitated with a control gate (CG). The WO₃ sensing layer is deposited on the interdigitated CG-FG of a field effect transistor(FET)-type gas sensor platform. The sensing layer is deposited with different thicknesses of the film ranging from 100 nm to 1 ㎛ by changing the deposition times during the sputtering process. The sensing characteristics of the fabricated gas sensor are measured at different NO₂ concentrations and operating temperatures. The response of the gas sensor increases as the NO₂ concentration and operating temperature increase. However, the gas sensor has an optimal performance at 180℃ considering both response and recovery speed. The response of the gas sensor increases significantly from 24% to 138% as the thickness of the sensing layer increases from 100 nm to 1 ㎛. The sputtered WO₃ film consists of a dense part and a porous part. As reported in previous work, the area of the porous part of the film increases as the thickness of the film increases. This increased porous part promotes the reaction of the sensing layer with the NO₂ gas. Consequently, the response of the gas sensor increases as the thickness of the sputtered WO₃ film increases.

• Carbon letters
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• v.12 no.1
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• pp.21-25
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• 2011

A novel electrode for an NO gas sensor was fabricated from electrospun polyacrylonitrile fibers by thermal treatment to obtain carbon fibers followed by chemical activation to enhance the activity of gas adsorption sites. The activation process improved the porous structure, increasing the specific surface area and allowing for efficient gas adsorption. The gas sensing ability and response time were improved by the increased surface area and micropore fraction. High performance gas sensing was then demonstrated by following a proposed mechanism based on the activation effects. Initially, the pore structure developed by activation significantly increased the amount of adsorbed gas, as shown by the high sensitivity of the gas sensor. Additionally, the increased micropore fraction enabled a rapid sensor response time due to improve the adsorption speed. Overall, the sensitivity for NO gas was improved approximately six-fold, and the response time was reduced by approximately 83% due to the effects of chemical activation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.294-298
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• 2004

Carbon nanotubes(CNTs) were synthesized by thermal chemical vapor deposition(CVD) method. To fabricate CNT gas sensor, catalyst metal layer was deposited on microstructure. The CNT gas detecting layer was grown by thermal CVD method on the catalyst metal layer. In order to investigate the gas sensing characteristics of the fabricated CNT gas sensor, it was exposed in NO$_2$ gas and sensitivity, response, and recovery time were measured. As the result, this sensor has better reproductibility and faster recovery time than another CNT gas sensors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.222-225
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• 2002

The nitrogen oxides, NO and NO2, abbreviated usually as NOx, emitted from combustion facilities such as power plants and automobiles are the typical air-pollutants causing acid rain and photochemical smog. In order to solve the NOx-related pollution problems effectively, we need efficient techniques to monitor NOx in the combustion exhausts and in environments. Development of solid-state electrochemical devices for detecting NOx is demonstrated based on various combination of solid electrolytes and auxiliary sensing materials. The object of this research is to develop various sensor performance for solid state amperometric sensor, and to test gas sensor performance manufactured. So we try to present a guidance for developing amperometric gas sensor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.924-926
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• 2000

The nitrogen oxides, NO and NO2, abbreviated usually as NOx, emitted from combustion facilities such as power plants and automobiles are the topical air-pollutants causing acid rain and photochemical smog. In order to solve the NOx-related pollution problems effectively, we need efficient techniques to monitor NOx in the combustion exhausts and in environments. Development of solid-state electrochemical devices for detecting NOx is demonstrated based on various combination of solid electrolytes and auxiliary sensing materials. The object of this research is to develop various sensor performance for solid state amperometric sensor, and to test gas sensor performance manufactured. So we try to present a guidance for developing amperometric gas sensor. We concentrated on development of manufacturing process and performance test.

• Journal of the Korean Ceramic Society
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• v.32 no.12
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• pp.1369-1376
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• 1995

The WO3 thin-film NOx sensor which is of practical use and includes the heater and the temperature sensor was fabricated. The WO3 thin films as a gas-sensing layer was deposited at ambient temperature in a high-vacuum resistance heated evaporator. The highest sensitivity of the WO3 thin-film sensor to NOx was obtained under the condition of the annealing temperature of 50$0^{\circ}C$ and the operating temperature of 30$0^{\circ}C$. The gas sensing characteristics of this sensor was excellent, i.e. high sensitivity (Rgas/Rair in 3 ppm NO2=53) and fast response time (4 seconds).

• Proceedings of the KAIS Fall Conference
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• 2006.05a
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• pp.223-226
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• 2006

The micro-gas sensor based on carbon nanotubes (CNTs) was fabricated and its gas sensing characteristics on nitrogen dioxide ($NO_2$) have been investigated. The sensor consists of a heater, an insulating layer, a pair of contact electrodes, and CNT-sensing film on a micromachined diaphragm. The heater plays a role in the temperature change to modify sensor operation. Gas sensor responses of CNT-film to $NO_2$ at room temperature are reported. The sensor exhibits a reversible response with a time constant of a few minutes at thermal treatment temperature of $130^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.17 no.2
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• pp.147-150
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• 2008

Multiple ZnO nanorod device detecting $NO_2$ gas was fabricated by sol-gel growth method and gas response characteristics were measured as a chemical gas sensor. The device is mainly composed of sensing electrode and sensing nano material. To acquire high sensitivity of the device for $NO_2$ gas it was heated by a heat chuck up to $400^{\circ}C$ The sensing part was easily made using the CMOS compatible process, for example, the large area and low temperature nano material growth process, etc. The sensors were successfully demonstrated and showed high sensitive response for $NO_2$ gas sensing.