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

This work reports the fabrication of ZnO single-nanowire (SNW) Schottky diode based-sensors with micro-cantilever printed AgNP contact pads, for room temperature (RT) detection of air pollutants such as CO ₂ and CO. ZnO SNWs with length in range of ~ 1-5 μm and diameter in the range of ~ 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 ppb to 9 ppm for CO ₂ and CO respectively. A higher sensitivity of 0.34%/ppm and 0.28%/ppm is obtained for CO ₂ and CO respectively. It is found that SDS treatment makes sensors more selective towards CO ₂ and CO. The fabricated sensors show a low response time mostly in a range of ~ 5-10 s and recovery time in a range of ~ 2-10 minutes. These sensors are stable within a relative humidity range of (15-75)%.