Highly sensitive SnO2 nanowire network gas sensors

In this work we present a methodology for the localized growth of nanowires on prespecified areas of micro -hotplates that allows to independently adjust the device's resistance and its response to the gas. This is achieved through the fabrication stripes containing the nanowires, with or without the presence of a gap in the stripe, giving rise that the nanowires bridge the current. The methodology is demonstrated growing SnO2 nanowire-based chemoresistors and the fabricated sensors have been characterized against CO and NO2. The results show the capability of tailoring nanowire stripe sizes from 1 to 100 mu m, including empty areas of the same sizes along the sensing material, and a response increase by a factor of up to 500. We attribute the response enhancement to the absence of nucleation seeds in the gap area, where only arching nanowires can allow the current to flow between electrodes. In this way, the current flow along the bridge of nanowires is restricted principally to the surface conduction, which is controlled by the interaction of the nanowires with gases.