Studying the Structural, Optical and Electrical Properties of ZnO: SnO2 Thin Films as an Application of a Gas Sensor Using Vacuum Thermal Evaporation Technique

Abstract

In this work, thermal evaporation in vacuum technique was used to prepare the ZnO thin films as pure and doped with SnO₂ NPs on glass substrates. The XRD pattern showed the hexagonal structure of ZnO with (002) preferred orientation. The EDX technique was used to investigate the contents of the film elements prepared which consisted of Zn, Sn and O. The concentration of Zn, O and Sn in the nanostructure films was different for all doping ratios. Thickness and morphology surface of the films were calculated from cross section of the surface films (~144 nm) using scanning electron microscopy images. The FE-SEM images confirmed the ZnO nanostructures and modifications of the morphology when adding SnO₂. The pure film deposited was dense and structured; while ZnO: SnO₂ (1,5 % wt) was a nanostructure. The optical band gap and Transmittance increased with the increase in the doping ratio of SnO₂, while the absorption spectrum decreased for the prepared thin films. The prepared films showed different responses to the gas sensing at two different operating temperatures (100, 200 ºC) and the doping ratio increased the sensor value of the gas at an optimum temperature of (200 ºC).