Dependence of Pt gate restructuring on the linearity of SiC Field Effect Transistor lambda sensors
2003 (English)In: Sensor Letters, ISSN 1546-198X (print) 1546-1971 (online), Vol. 1, no 1, 37-41 p.Article in journal (Refereed) Published
To achieve an efficient conversion of pollutants from gasoline-driven cars, the lambda value, or the air-to-fuel ratio, of the exhausts that reach the catalytic converter is required to be close to 1. The composition of the exhaust gases is normally regulated with the use of a zirconia lambda sensor. However, at cold start another, more robust sensor is required, and a SiC-based field effect transistor sensor is currently being developed for this purpose. The SiC field effect transistor sensor has previously been shown to respond in either a linear or a binary fashion to changes in the lambda value, depending on parameters such as the choice of operation temperature and the area of catalytic metal. Here it is shown that the linear behavior of the sensor may appear as a result of the restructuring of the thick Pt film, which is working as its sensitive layer, when exposed to intermittent pulses of reducing and oxidizing gas mixtures. Sensors that have been used only for a short while have a continuous film and show a binary behavior, whereas samples that have been run for a longer time have seriously restructured films and show a linear behavior. A connection between the linear behavior and the decreased catalytic activity of the used films in comparison with fresh samples with a binary behavior is discussed. Some alternative methods for preventing the restructuring of the metal are suggested.
Place, publisher, year, edition, pages
2003. Vol. 1, no 1, 37-41 p.
IdentifiersURN: urn:nbn:se:liu:diva-13403DOI: 10.1166/sl.2003.011OAI: oai:DiVA.org:liu-13403DiVA: diva2:20674