Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions

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A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device, Pt/SiO{sub 2}/SiC that can detect hydrogen-containing species in chemically reactive, high temperature (600 C) environments. We demonstrate that the device can be used as a hydrogen monitor in syngas applications of common interferants as well as sulfur and water vapor. These measurements were made in the Catalyst Screening Unit at NETL, Morgantown under atmospheric conditions. The sensor response to hydrogen gas at 350 C is 240 mV/decade, ... continued below

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Ghosh, Ruby; Loloee, Reza & Tobin, Roger September 30, 2008.

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A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device, Pt/SiO{sub 2}/SiC that can detect hydrogen-containing species in chemically reactive, high temperature (600 C) environments. We demonstrate that the device can be used as a hydrogen monitor in syngas applications of common interferants as well as sulfur and water vapor. These measurements were made in the Catalyst Screening Unit at NETL, Morgantown under atmospheric conditions. The sensor response to hydrogen gas at 350 C is 240 mV/decade, this is significantly higher than the device response to room temperature gas or that predicted from vacuum chamber studies. The enhanced catalytic activity of the platinum sensing film under energy plant operating conditions was investigated via AFM, x-ray diffraction, TEM and x-ray photoelectron spectroscopy. Our characterization indicated that exposure to high temperature gases significantly modifies the morphology of the Pt catalytic film and the Pt/SiO{sub 2} interfacial region, which we tentatively attribute to the enhanced hydrogen sensitivity of the sensing film. A model for the hydrogen/oxygen response of the SiC device under atmospheric conditions was developed. It is based on two independent phenomena: a chemically induced shift in the metal-semiconductor work function difference and the passivation/creation of charged states at the SiO{sub 2}-SiC interface. The optimum operating set point for the SiC sensor with respect to response time and long term reliability was determined to be close to mid-gap. Ultrahigh vacuum (UHV) techniques were used to investigate the effects of sulfur contamination on the Pt gate. Exposure to hydrogen sulfide, even in the presence of hydrogen or oxygen at partial pressures of 20-600 times greater than the H2S level, rapidly coated the gate with a monolayer of sulfur. Although hydrogen exposure could not remove the adsorbed sulfur, oxygen was effective at removing sulfur with no evidence of irreversible changes in device behavior. The role of oxygen in the functioning of the SiC sensors was also investigated. All of the results are consistent with oxygen acting through its surface reactions with hydrogen, including the need for oxygen to reset the device to a fully hydrogen-depleted state and competition between hydrogen oxidation and hydrogen diffusion to metal/oxide interface sites. A strong sensor response to the unsaturated linear hydrocarbon propene (C{sub 3}H{sub 6}) was observed.

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  • Report No.: None
  • Grant Number: FC26-03NT41847
  • DOI: 10.2172/961522 | External Link
  • Office of Scientific & Technical Information Report Number: 961522
  • Archival Resource Key: ark:/67531/metadc931110

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • September 30, 2008

Added to The UNT Digital Library

  • Nov. 13, 2016, 7:26 p.m.

Description Last Updated

  • Dec. 8, 2016, 11:03 p.m.

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Ghosh, Ruby; Loloee, Reza & Tobin, Roger. Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions, report, September 30, 2008; United States. (digital.library.unt.edu/ark:/67531/metadc931110/: accessed September 25, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.