Ultra-thin oxide films as gas microsensors
A mixed metal layered oxide of titanium and niobium was used as a novel chemiresistor for gas sensing. The oxides were exfoliated and deposited onto 1 μm gap electrodes. Thin layers of the oxides (∼22 nm) were obtained and investigated for their electrical properties in the presence of these analyte gases; ammonia, methanol, ethanol, butanol, hexanol, and acetone. At room temperature operation and in the presence of ambient humidity, it was found that the oxide films behaved as an n-type semiconductor. The sensors generally showed good response for high concentrations of the gases. The sensor showed a very good response to ammonia, with the lowest concentration tested showing good detection at 200 ppm. For the alcohols, the sensors were found to have the best response to methanol, with the lowest detection being at 1000 ppm. It was postulated that the response is due to the high polarity of methanol with respect to the other alcohols. The response observed in acetone was good but not as good as methanol and ammonia. The sensitivity to the analyte gases was, in decreasing order, ammonia, methanol, ethanol, acetone, butanol and hexanol. The response time in general was impressive with rise times of less than 15 seconds. The recovery period was found to be slow as the sensors were operated at low temperature. This experiment has provided interesting and challenging results for new sensing films in metal oxide gas sensor technology. However, further investigations are needed to improve the sensitivity and selectivity of these new sensors.
Bubphamala, Teerada, "Ultra-thin oxide films as gas microsensors" (2006). ETD Collection for University of Texas, El Paso. AAI3196423.