Microtech 2011

Tin oxide nanowire sensors for highly sensitive detection of toxic gases

A. Koeck, E. Brunet, C. Griessler, T. Maier, G. Mutinati, S. Steinhauer
AIT Austrian Institute of Technology GmbH, AT

Keywords: nanosensors, gas sensors, nanowires


Numerous applications ranging from industrial process control to personal safety systems and environmental monitoring have a strongly increasing demand for highly sensitive gas detecting devices. We present nanosensors based on SnO2-nanowires, which are extremely sensitive to the highly toxic gases SO2 and H2S. The nanowires are realized in a two-step atmospheric pressure synthesis process on Si-substrates: In a first step nanocrystalline SnO2-films with thickness ~200 nm are fabricated by a spray pyrolysis process, the second process is an annealing process at 900°C The whole SnO2-nanowire fabrication procedure is performed at atmospheric pressure and requires no vacuum. A SO2 gas concentration of 26.8 ppm results in a maximum signal of ~6% at 400°C. A H2S concentration of only 1.4 ppm results in maximum signal of 30% at 400°C. This very high sensor signalsdemonstrates extraordinary sensitivity of the nanowire sensors with a resolution in the ppb range. The sensors are able to measure concentrations well below their respective threshold limit values (SO2: 2ppm, H2S: 10ppm). The different behaviour (increase and decrease of sensor resistance) should basically allow for a clear discrimination between the two test gases.

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