Switching the selectivity of ZnO thin films for ultra-sensitive acetaldehyde gas sensors through Co doping

Pure and Co doped (1-5 wt%.) ZnO thin films were synthesised using the chemical spray pyrolysis method for the detection of acetaldehyde at 300 K. The gas sensing properties of these films were studied. The preferential orientation of the films along the c-axis stated its high crystalline nature. The responsiveness of the Co doped films switched to acetaldehyde from ammonia of the pure ZnO film. The 5 wt%. Co doped ZnO films could effectively detect 5 ppm of acetaldehyde at 300 K with a better response of around 238, compared to the pure and other doping concentrations. This high response is due to the catalytic property of Co, whose presence changed the electrical properties of the film. Co2+ created Zn2+ vacancies over the surface and generated defects, promoting the gas sensing mechanism. The constructed sensing layer is stable and repeatable implying its potential application as an acetaldehyde gas sensor.