Ultrasensitive nitric oxide gas sensors based on Ti-doped ZnO nanofilms prepared by RF magnetron sputtering system

It is aimed to explore the advantages of titanium doping and magnetron sputtering as opposed to chemical-based methods on the surficial and electrical characteristics of ZnO films and their gas sensing performance in particular. RF magnetron sputtering was employed to synthesize a pure ZnO nanofilm as a reference and Ti-doped ZnO nanofilms with various Ti contents. The doping process was done by sputtering Ti-doped ZnO targets developed through solid-state reaction, and doping content was determined by EDS analysis. All nanofilms exhibited pure hexagonal wurtzite structure and relatively flat and homogenous surfaces with a clear distribution of nanoparticles in the Ti-doped samples. The observed enhancement in the properties of the nanofilms was reflected in the ultimate performance of the gas sensor. In this regard, the sensor with 1 wt% Ti content showed the best gas sensing performance with an ultra-sensitivity of 1.72 for 1 ppm and 0.9 for 1 ppb NO gas at a relatively low working temperature of 167 °C. The sensor also acquired outstanding stability, quick responsivity, reproducibility and superior selectivity required for NO monitoring.