SiC-FET methanol sensors for process control and leakage detection

Two types of SiC based field effect transistor sensors, with Pt or Ir gate, were tested to detect methanol in in the concentration range of 0-1600 ppm for both process control and leak detection applications. The methanol methanol response was investigated both with and without oxygen, since the process control might be considered considered as oxygen free application, while the sensor is operated in air during leak detection. Pt sensors offered offered very fast response with appreciably high response magnitude at 200 degrees C, while Ir sensors showed both both higher response and response time up to 300 degrees C, but this decreased considerably at 350 degrees C. Crosssensitivity sensivity effect in presence of oxygen, hydrogen, propene and water vapor was also investigated. The presence presence of oxygen improved the response of both sensors, which is favorable for the leak detection application. application. Hydrogen had a large influence on the methanol response of both sensors, propene had a negligible negligible influence, while water vapor changed direction of the methanol response for the Pt sensor. The detection mechanism and different sensing behavior of Pt and Ir gate sensors were discussed in the light light of model reaction mechanisms derived from hybrid density-functional theory quantum-chemical calculations. (C) 2013 Elsevier B.V. All rights reserved.