Development of ZnO sensors via succession ionic layer adsorption and reaction (SILAR) method for ppb level NO gas sensing

In this work, the effects of Cd doping on the gas sensing properties of ZnO thin films were synthesized by SILAR method and studied gas sensing characteristics against NO, CO, ammonia, methanol, and acetone systematically. Whereas the operating temperature of NO gas was found to be 90 °C, CO and acetone were 150 °C and 170 °C. The response was not observed in methanol and ammonia gases. Especially, it was observed that the response continued to increase as the temperature increased for methanol gas. In addition, the 5% Cd-doped ZnO sensor exhibits excellent selectivity for NO compared to other test gases as ∼12% at 0.01 ppm. NO gas sensing reactions are accelerated with Cd doping because Cd doping created increasing oxygen vacancies, surface chemisorbed oxygen species, and defects in the lattice.