Influence of Sn doping on CO and CO2 sensing of ZnO thin films prepared by spray pyrolysis method

Abstract

Sn doped ZnO nanostructured thin films are deposited by ultrasonic spray pyrolysis method on glass substrate at 400°C temperature with Sn doping of 1, 3, 5, 10, and 15 mol% in ZnO. The thin films are characterized by XRD, SEM, and UV-Visible spectroscopy. For all the films, XRD analysis show the polycrystalline nature with hexagonal wurtzite structure. With the variation of Sn concentration in ZnO thin films, morphology changes from nanowires to nanoflakes. For 10 mol% Sn doped ZnO thin films, nanoflakes morphology is evidently observed. The value of optical gap obtained from UV-Visible spectroscopy shows the decrease in the band gap with Sn doping in ZnO. The band gap decreases from 3.1 eV to 2.94 eV. Improvement in electrical properties with dopant concentrations is observed. Further, the sensitivity of the Sn doped samples investigated towards CO and CO2 gases at room temperature. Sn doped ZnO thin films show higher sensitivity towards CO gas as compared to that of CO2 gas. 10 mol% of Sn doped ZnO thin film show the highest sensitivity towards CO and CO2 gases among all concentrations as well as compared to that of ZnO thin film. The concentration dependent morphological variations are playing important role in sensing mechanism.