An investigation in to the impact of Ti doping on the structural, optical and sensing properties of spray deposited nanocrystalline ZrO2 thin films

Pure and Ti doped ZrO2 thin films were prepared by chemical spray pyrolysis method on a glass substrate at 450 °C. XRD results reveal that pure and doped films had polycrystalline structure in nature with tetragonal phase and highly oriented along (011) plane. The crystallite size was increased with increasing Ti content from 17.6 nm to 25.3 nm. SEM images of ZrO2 and ZrO2:Ti thin films showed that the surface seems relatively homogeneous, and the EDX spectra confirm the stoichiometry of the prepared films. AFM measurements showed that the average roughness values were increased after doping with Ti. Optical transmittance of the deposited films high value was about (50%) and decreased with increasing of dopant concentration. The optical band gap decreased from 4.30 eV to 3.01 eV with increasing of Ti content. The ZrO2 and ZrO2:Ti (8%) thin films were investigated as NO2 gas sensor, the results showed a maximum response was at 250 °C and had a stable behavior for detecting NO2 gases. The doped ZrO2 film illustrated a higher response than that of the pure film. The sensing mechanism was modeled according to the oxygen-vacancy mode.