Influence of AACVD Temperature on the Microstructural and Gas Sensing Properties of ZnO Thin Films

Thin zinc oxide films were synthesized via the AACVD method, with the synthesis temperature being the variable parameter, ranging from 350 to 500°C. The obtained ZnO particles were found to have a wurtzite structure with an average crystallite size of 26 ± 4 nm. Morphological analysis revealed that within the temperature range of 400–450°C, continuous films with an average particle size of 52 ± 14 nm are formed, whereas at synthesis temperatures of 350–375 and 475–500°C, films with an island-like morphology and an average size of 51 ± 13 nm are observed. The optical properties of the films were investigated, yielding estimated band gap values of 3.31–3.34 eV. A growth mechanism dependent on the synthesis temperature is proposed. The chemosensing properties of the films were studied at operating temperatures of 150–350°C using a wide range of analyte gases: CO, NH3, H2, CH4, C6H6, ethanol, acetone, and NO2. The thin films demonstrated high sensitivity (4–100 ppm) to volatile organic compounds (VOCs) at an operating temperature of 350°C. It was established that the sample with the highest surface roughness exhibited the greatest sensor response. The influence of humidity on the magnitude and shape of the signal obtained during acetone detection was also investigated.