Modifications of the Gate Material to Increase the Long-Term Stability of Field Effect Transistor Lambda Sensors
2005 (English)In: Sensor Letters, ISSN 1546-198X, Vol. 3, no 3, 225-230 p.Article in journal (Refereed) Published
The MISiC-FET Pt/TaSix sensor has been shown previously to work well for measuring the lambda value, or the air-to-fuel ratio, of gasoline engine exhausts. However, the catalytic gate metal that is crucial for the sensing properties tends to restructure in harsh exhaust gases, which affects the behavior of the device. To increase the long-term stability of the sensor several modifications of the sensing layer, such as depositing a protective film of SiO2 on top of the metal or co-sputtering the catalytic metal with SiO2, have been studied and are presented here. The sensitivity and long-term stability of these films compared to the Pt/TaSix layers traditionally used for MISiC-FET lambda sensors have been investigated through laboratory measurements and SEM (scanning electron microscope) analyses. It was found that the catalytic metal films with a protective layer restructured much less than those without, but that the protective layer decreased the sensitivity of the sensors. On the other hand, the sensor gained linear characteristics when exposing it to lambda stairs. Mixing Ir and SiO2 also gave less restructuring compared with the reference samples, while maintaining a high sensitivity to lambda.
Place, publisher, year, edition, pages
2005. Vol. 3, no 3, 225-230 p.
Cold start sensors; Sic-fet; Lambda; Long-term stability; Linear
IdentifiersURN: urn:nbn:se:liu:diva-13411DOI: 10.1166/sl.2005.034OAI: oai:DiVA.org:liu-13411DiVA: diva2:20683