Cr-doped ZnO based NO2 sensors with high sensitivity at low operating temperature

NO2 sensors with high sensitivity at low operating temperature were prepared by growing Cr-doped ZnO nanorods on Al2O3 substrate with spiral or interdigitated electrodes. The sensitivity reached 270%, 335% and 635% corresponding to 2, 3 and 5 ppm NO2 at 100 °C, respectively. Surface morphology and crystal structure of the doped ZnO nanostructure were monitored by FESEM, HRTEM, and XRD. Effects of dopant precursor concentration, calcination temperature, nanorod growth time, operating temperature and electrode geometry on the NO2 gas sensing properties were investigated. Using spiral electrodes and incorporating Cr dopant in ZnO nanorods lead to increased sensitivity and reduced operating temperature of the gas sensor.