AVS 52nd International Symposium
    Applied Surface Science Monday Sessions
       Session AS-MoP

Paper AS-MoP21
UHV Studies of Silicon Carbide Gas Sensors with Catalytic Platinum Gates

Monday, October 31, 2005, 5:00 pm, Room Exhibit Hall C&D

Session: Aspects of Applied Surface Science Poster Session
Presenter: Y.H. Kahng, Tufts University
Authors: Y.H. Kahng, Tufts University
R.G. Tobin, Tufts University
R.N. Ghosh, Michigan State University
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We have studied the sensing response and surface chemistry of silicon carbide (SiC)-based gas sensors with catalytic platinum gates, in ultrahigh vacuum. Silicon carbide's large bandgap (2.4 - 3.3 eV), native oxide, and rugged physical properties make it an attractive material for use in extreme environments, including corrosive gases and temperatures up to 1000 K. Possible applications include coal burners and gasification facilities. Catalytic-gate devices based on SiC have shown response to hydrogen and hydrogen-containing gases over a wide concentration range, but details of the transduction mechanism are not fully understood. We report UHV studies of the surface chemistry and sensing behavior of prototype Pt-SiO@sub 2@-SiC sensors, aimed at a detailed understanding of the role of the catalytic gate in abstracting hydrogen from the analyte, providing pathways from the gate surface to the oxide interface, and catalyzing oxidation of hydrogen desorbed from interface sites. Issues investigated include sensor response to varying partial pressures of hydrogen and oxygen and changes in gate properties resulting from gas exposure at elevated temperatures (600 - 800 K). Because sulfur is a contaminant in most fossil fuels and a notorious poison for catalysts, effects of sulfur contamination have also been studied.