Evaluation of hydrogen and ammonia gas mixtures with the suspended- gate field-effect transistor sensor array

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Generation of hydrogen represents a severe industrial hazard primarily because the mixture of hydrogen with air in the ratio 4.0--74.2 vol % is explosive. In some industrial applications, such as waste remediation, hydrogen, as a product of radiolysis and corrosion, occurs in the presence of ammonia, nitrous oxide, water vapor and other molecules. A low cost, reliable method for monitoring these gaseous mixtures is essential. Palladium-based layers have been used successfully as hydrogen sensitive layers in several potentiometric sensors for many years. Since the sensing mechanism is based on the catalytic decomposition of hydrogen molecules, other hydrogen-bearing gases can also ... continued below

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11 p.

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Domansky, K.; Li, H.S.; Josowicz, M. & Janata, J. December 1, 1995.

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  • Pacific Northwest Laboratory
    Publisher Info: Pacific Northwest Lab., Richland, WA (United States)
    Place of Publication: Richland, Washington

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Generation of hydrogen represents a severe industrial hazard primarily because the mixture of hydrogen with air in the ratio 4.0--74.2 vol % is explosive. In some industrial applications, such as waste remediation, hydrogen, as a product of radiolysis and corrosion, occurs in the presence of ammonia, nitrous oxide, water vapor and other molecules. A low cost, reliable method for monitoring these gaseous mixtures is essential. Palladium-based layers have been used successfully as hydrogen sensitive layers in several potentiometric sensors for many years. Since the sensing mechanism is based on the catalytic decomposition of hydrogen molecules, other hydrogen-bearing gases can also produce a response. From this viewpoint, using an array of sensing elements with catalytic and noncatalytic chemically selective layers in these applications can be highly effective. Moreover, integration of this array on a single chip can be routinely achieved. The Suspended Gate Field-Effect Transistor (SGFET) is microfabricated in silicon. The metal gate of the transistor is separated from the substrate by an air gap. The chemically sensitive layer is electrodeposited on the bottom of the suspended gate. Chemical species can penetrate into the gate area and interact with the sensing layer. This interaction modulates the work function of the layer. The change in the work function results in the shift of the transistor threshold voltage. The measured threshold voltage shift is a function of the gas concentration in the sensor vicinity. By passing a small current through the suspended gate, it is possible to control the operating temperature of the sensing layer (up to 200{degrees}C) and, therefore, to modulate the sensor sensitivity, selectivity, response and recovery times. Due to the very low thermal mass, the heat is localized on the gate so that many devices can be operated on a single chip, each with the gate at different temperature.

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11 p.

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OSTI as DE96004381

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  • International chemical congress of Pacific Basin Societies, Honolulu, HI (United States), 17-22 Dec 1995

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  • Other: DE96004381
  • Report No.: PNL-SA--26095
  • Report No.: CONF-951205--2
  • Grant Number: AC06-76RL01830
  • Office of Scientific & Technical Information Report Number: 192555
  • Archival Resource Key: ark:/67531/metadc668812

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  • December 1, 1995

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  • June 29, 2015, 9:42 p.m.

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  • April 7, 2016, 2:39 p.m.

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Domansky, K.; Li, H.S.; Josowicz, M. & Janata, J. Evaluation of hydrogen and ammonia gas mixtures with the suspended- gate field-effect transistor sensor array, article, December 1, 1995; Richland, Washington. (digital.library.unt.edu/ark:/67531/metadc668812/: accessed October 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.