Supersensitive Si-integrated tin oxide nanowire-sensors for gas detection

In this paper supersensitive gas sensors incorporating single SnO₂-nanowires integrated on Si for the detection of gases relevant to environmental and safety issues are presented. The SnO₂-nanowires are produced by a spray pyrolysis process followed by subsequent tempering, which results in growth of single-crystalline SnO₂-nanowires with diameters of 30 - 250 nm and lengths up to several 100 mum. TEM-analysis reveal the single crystalline character of SnO₂-nanowires with two preferred growth directions. The nanowires are removed from their substrate and transferred to another Si-substrate coated with 750 nm SiO₂. Evaporation of metal contact pads on both ends of single SnO₂-nanowires enable their direct use as sensing elements. The devices are very sensitive and are able to detect concentrations of CO and CH₄ as low as a few ppm.