Methodology for a one step fabrication of gas sensors using flame spray pyrolysis

• Applicants: Professor Dr.-Ing. Lutz Mädler; Professor Dr. Udo Weimar
• Subject Area: Analytical Chemistry ; Microsystems
• Term: from 2009 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 103134545

• Final Report Year: 2008

Final Report Abstract

Metal oxide sensors consume – depending on the used material – different test gases in different ways and by that specifically alter the gas composition. In this study it was possible to show that, by the use of this effect, selectivity can be created when using identical sensors and already existing selectivity when using different ones can be enhanced. By using different experiments and simulations the best conditions that allow for the use of gas consumptions as a selectivity enhancer were determined. In first line these are: • Equidistant sensor arrangement. - This action prevents the appearance of an irregular temperature gradient along the sensor chamber and thus reduces the convection. • Narrow sensor chamber. - This action allows more test gas molecules to reach the sensor surface at the same time. Therefore, the gas consumption is increased and the selectivity improved. • Huge sensor chamber opening and a short diffusion barrier. - Already between the sensor chamber opening and the first sensor the concentration decreases. This action allows the first sensor to detect the test gas almost in the original concentration and therefore to increase the sensitivity of the system. It was demonstrated, that already very simple simulation experiments are suitable to describe the experimental results in the case of setups with a regular sensor arrangement. However, a complex temperature gradient makes the consideration of the convection necessary. This might cause problems for the miniaturization of the whole system as it is. A promising way to simplify the setup is also to use the observed selectivity effect by adding several layers onto the same substrate. The present setup can serve as model system in order to find the appropriate materials for further experiments. It was shown that already two sensors in an appropriate sensor chamber are enough to create selectivity. The goal of further studies should be a simplification by adapting these advantages already on one sensor by the use of different layers.

Publications

• “Increase of the Selectivity of Sensor Arrays through Consumption Effects of Metal Oxide Sensors”, Eurosensors XXI, 2007, Lyon, France, 10-14 June 2007, p.2019-2022
  F. Röck, N. Barsan and U. Weimar