Structural, morphological and gas sensing properties of Zn1−xSnxO thin films by SILAR method

This paper presents the preparation of Zn1−xSnxO thin films by Successive Ionic Layer Adsorption and Reaction (SILAR) method and a systematic investigation of their low-level NO gas detection properties. By changing Sn dopant ratio “x” from 0 to 1 with 0.25 increment steps, a wide range analysis from pure ZnO to pure SnO2 was carried out. X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDAX) and optical absorption measurements were used in the characterization of the synthesized films. Characterization data showed that the films have polycrystalline nature with hexagonal wurtzite (pure ZnO) and tetragonal (pure SnO2) structure and that the increase in the concentration of Sn dopant leads to an increase in the optical bandgap and a decrease in the average crystallite size. The 25% Sn doping value gave the smallest dislocation density, and the film with this doping value showed the best crystalline structure among all others. From SEM images, different doping ratios appeared to affect the distribution of surface particles. And by gas sensing analysis, the individual responses of the synthesized sensors to 100 ppb NO gas were examined, among which Zn0.75Sn0.25O recorded the highest responsivity of 37% at 55 °C as well as the highest selectivity towards NO gas as compared with other control group gases, and the latter was also proved through principal component analysis (PCA). Doping- and temperature-dependent gas sensing analysis can provide quite efficient information on the sensing mechanism of metal oxide semiconductor (MOS) materials. It was concluded from the measurements that Sn doping has a significant effect on gas sensing properties with 25% doping value regarded as the optimal doping value within the investigated series. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.