Development of solid-state catalytic filters for enhancement of the performance of field effect based gas sensors

The wide band gap of the semiconductor material silicon carbide (SiC) permits its use at elevated temperatures and the material is also chemically inert, what makes it suitable for use in aggressive environments. On application of a catalytic gate material gas sensitive field effect transistor devices based on SiC can be realized and have also been shown to exhibit good properties for high temperature applications such as combustion control and monitoring of car exhaust after-treatment systems.

The sensor devices developed so far have proven robust but merely gives a measure of the total amount of emissions or the emissions level in relation to the oxygen level. Monitoring of concentrations of individual exhaust or flue gas species (like CO and NO/NO2) is possible only for certain species (like H2 and NH3) under very special conditions.

One way of getting around this problem would be to allow just the specie/species one is interested to gain information about to reach the sensor surface. Some work has already been done in this area for other sensor technologies and it has been shown that it might be possible to construct filters that catalytically and selectively remove certain species from a gas stream, while leaving some other substance/s more or less unaffected. In the case of SiC based field effect gas sensors other considerations have to be taken into account when developing such filters as compared to other sensor technologies, partly due to a different response mechanism, why it is not possible just to copy the results from other investigations.

A diploma work in this field would thus be composed of a short theoretical investigation regarding suitable materials and methods for the manufacturing of such filters as well as processing and testing of some different filter materials. The main goal is to be able to separate one of the following gas species from the others; CO, NO/NO2 and propene (C3H6) A more detailed plan for the diploma work will be set up when a proper introduction to the subject and some time to study background information has been given, and can to a large extent be influenced by the student herself/himself.

Suitable Background: Chemistry and / or physics

Supervisor: Mike Andersson [email protected] 013 281372
Examiner: Anita Lloyd Spetz [email protected] 013 281710
S-SENCE and Div of Applied Physics, Linköping University, Sweden