Abstract
A device for detection of short gas pulses at very low concentrations is presented. The approach is based on a special temperature modulation technique enabling a differential surface reduction (DSR) measurement of a metal oxide semiconductor (MOS) gas sensor. With this method, the sensor surface is highly covered with oxidized surface states at high temperature (e. g. 400 °C) initially. The temperature is then reduced abruptly to, e. g., 100 °C resulting in a state with strong excess of negative surface charge. Reactions of these surface charges with reducing gases are prevailing and lead to very high sensitivity. For the measurement a dedicated detector (electronics and fluidic system) is presented. The electronics allows a high-resolution conductance measurement of the sensitive layer and accurate temperature control. The fluidic system is examined in terms of peak shape and optimal sensor response via FEM simulations.
Zusammenfassung
Ein Messsystem zur Detektion von kurzen Gaspulsen bei sehr niedrigen Konzentrationen wird vorgestellt. Der Ansatz basiert auf einem speziellen Temperaturmodulationsverfahren, das eine differentielle Messung der Oberflächenreduktion (DSR) eines Metalloxid-Halbleiter-Gassensors (MOS) ermöglicht. Bei diesem Verfahren wird die Sensoroberfläche bei hoher Temperatur (z. B. 400 °C) oxidiert. Ein abrupter Temperatursprung auf z. B. 100 °C führt zu einem Zustand mit starkem Überschuss an negativer Oberflächenladungen. Reaktionen dieser Oberflächenladungen mit reduzierendem Gas sind vorherrschend und führen zu einer sehr hohen Empfindlichkeit. Für die Messung wird ein eigen entwickelter Detektor (elektronisches und fluidisches System) vorgestellt. Die Elektronik ermöglicht eine hochauflösende Leitwertmessung der sensitiven Schicht und eine genaue Temperaturregelung. Das fluidische System wird mittels FEM-Simulationen auf Peakform und optimale Sensorresponse untersucht.
About the authors
Tobias Baur studied microtechnology and nanostructures at Saarland University and received his master’s degree in 2016. He is currently a Ph.D. student at the Lab for Measurement Technology at Saarland University and focuses on the model-based temperature cycled operation of gas sensors, the development of gas sensor electronics and the measurement of short trace gas pulses.
Caroline Schultealbert studied microtechnology and nanostructures at Saarland University and received her master’s degree in 2015. She is currently a Ph.D. student at the Lab for Measurement Technology at Saarland University and focuses on the model-based temperature cycled operation of gas sensors, their calibration and emission materials and the optimization of the corresponding systems via FEM simulations.
Andreas Schütze studied Physics and received his doctorate in Applied Physics from Justus-Liebig-Universität in Gießen in 1994 with a thesis on micro gas sensor systems. After some years in industry, he joined the University of Applied Sciences in Krefeld, Germany, as professor for Microsystems Technology from 1998 to 2000. Since 2000 he is a full professor for measurement science and technology in the Department Systems Engineering at Saarland University, Saarbrücken, Germany. His research interests include microsensors and microsystems, especially advanced chemical sensor systems, both for gas and liquid phase, for security and control applications.
Tilman Sauerwald received his PhD in 2007 at the University of Giessen working on the influence of surface reactions to the multi-signal generation of metal oxide sensors. Since 2011 he is working at the Lab of Measurement Technology at the Saarland University. His current focus is the detection of trace gases by developing of model-based techniques for multi-signal generation.
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