H2S sensing in the ppb regime with zinc oxide nanowires

In this work, we investigate the hydrogen sulfide (H2S)-gas-sensing-properties of zinc oxide (ZnO) nanowires. By a common chemical vapour deposition (CVD) process ZnO nanowires were grown on silicon (111) using a mixture of ZnO and graphite powder as source material. Subsequently, the nanowires were separated from the substrate and placed on a metal contact structure using dielectrophoresis. The sensing properties of the nanowires were tested in a temperature stabilized setup. Applying a constant voltage and exposing to H2S leads to an increase of the current through the nanowires. Especially the role of oxygen in the sensing mechanism has been investigated using different gases for flushing. We demonstrate that oxygen is crucial for the reset of the sensor and multiple sensing cycles with one sensor were realized. The ZnO nanowires show a very high sensitivity and a H2S concentration of only 50 ppb can be detected.