Low operating temperature of UV photo-activated In-doped ZnO NO2 sensors

Indium-doped ZnO (IZO) nanopowders with different In loading (1 at.%, 3 at.% and 5 at.%) have been synthesized by the sol-gel method Characterization analysis was carried out for evaluating the morphological and microstructural properties of the synthesized IZO samples. XRD analysis revealed that the IZO nanopowders are polycrystalline and exhibited a hexagonal wurtzite structure. The average crystallites size was found to decrease with the incorporation of indium dopant. Resistive sensors based on the pure and IZO nanopowders have been fabricated and tested towards NO2 monitoring at low concentrations in air in both dark and under ultraviolet (UV) illumination at lambda = 380 nm. Results demonstrated that the baseline resistance of the sensors was reduced because of In doping and UV irradiation. Thus, IZnO-based resistive sensors were able to work at near room temperature (T = 50 degrees C) in presence of UV light, reaching a high gas response S = R-g/R-a of 8.4 towards 5 ppm of NO2 and a limit of detection (LOD) of 250 ppb. These results demonstrate that the developed devices are promising NO2 sensors for practical applications.