Conductometric ethanol gas sensor based on a bilayer film consisting of SnO2 film and SnO2/ZnSnO3 porous film prepared by magnetron sputtering

As one important type of the sensing material, the metal oxide film can realize accurate detection to the low concentration of ethanol. In this paper, a double-layer nano film was prepared by sputtering a SnO2 bottom layer and co-sputtering a SnO2/ZnSnO3 porous top layer with SnO2 and ZnO targets. Firstly, the effects of Zn content on the properties of the single-layer SnO2/ZnSnO3 porous film were investigated by changing sputtering power of ZnO and keep sputtering power of SnO2 constant. When the sputtering power of ZnO is 25 W, the single-layer SnO2/ZnSnO3 porous film has the best response to ethanol. To expose more adsorption sites to air, the SnO2/ZnSnO3 porous layer was deposited on a SnO2 thin film with thickness of 10 nm to form the double-layer sensing material. The double-layer thin film has response of 11.5–50 ppm ethanol at 290 °C, which is 2.1 times that of the single-layer SnO2/ZnSnO3 porous layer, and the response and recovery time of the double layer are 56 s and 666 s to 50 ppm ethanol at 290 °C, which are shortened by 63 s and 641 s compared to those of the single layer, respectively. In addition, the double-layer porous film also exhibits excellent long-term stability and good selectivity to ethanol. The n-n heterojunction formed between SnO2 and ZnSnO3 and unique double-layer porous structure are the main reasons for the excellent sensing performance.