Room Temperature Air Pollutants Sensors Using Printed ZnO Single-Nanowire Schottky Diodes

This work reports the fabrication of ZnO singlenanowire (SNW) Schottky diode based-sensors with microcantilever printed AgNP contact pads, for room temperature (RT) detection of air pollutants such as CO2 and CO. ZnO SNWs with length in range of similar to 1-5 mu m and diameter in the range of similar to 90-250 nm have been placed on a silicon substrate by drop-casting an optimized dispersion of ZnO nanowires in de-ionised (DI) water. ZnO nanowire dispersion is further optimized by adding sodium dodecyl sulfate (SDS) and acetic acid to form longer nanowires which ease the reproducibility and scaling of the fabrication process. The sensors demonstrate a wide gas-sensing range of 500 ppb to 500 ppm and 10 pph to 9 ppm for CO2 and CO respectively. A higher sensitivity of 0.34%/ppm and 0.28%/ppm is obtained for CO2 and CO respectively. It is found that SDS treatment makes sensors more selective towards CO2 and CO. The fabricated sensors show a low response time mostly in a range of similar to 5-10 s and recovery time in a range of similar to 2-10 minutes. These sensors are stable within a relative humidity range of (15-7 5)%.