Synthesis of fast response, highly sensitive and selective Ni:ZnO based NO2 sensor

Abstract

The use of metal oxide semiconductor (MOS) gas sensors is limited due to lack of selectivity and high operating temperature. The aim of present investigation is to enhance gas response and sensitivity of the zinc oxide (ZnO) based thin film sensor towards nitrogen dioxide (NO2) by Ni doping. The achieved sensitivity is around 4.2%/ppm at moderate operating temperature of 200°C. The gas response of 108% and 482% is observed at 200°C operating temperature, towards 5ppm and 100ppm NO2, respectively. Ni doping increased the NO2 response and reduced the lower detection limit of NO2 to 5ppm which is much lower than the emergency exposure limit (20ppm). The hybrid structure of nanograined rods and hexagonal flakes are observed which enhanced gas response. The gas response dependence on various physical properties and chemical composition of the sensor is also studied. The response and recovery time of 1.5 atomic percentage (at%) Ni doped ZnO thin film sensor is 11 and 123s, respectively. The response of the sensor is reproducible and it has negligible cross sensitivity for other interfering gases such as CO2, SO2, H2S, NH3, LPG, methanol, ethanol, and acetone.