Fabrication of Ni-doped ZnO thin films via spray pyrolysis method towards highly selective and sensitive acetone gas sensing

Nickel-doped zinc oxide (NiZ) thin films were synthesized on glass substrates using the spray pyrolysis deposition technique, with nickel concentration varying from 0 to 3 %. The structural, morphological, elemental analysis, optical, photoluminescent and acetone gas sensing characteristics at elevated temperatures were analyzed about Ni-doping concentrations. The XRD analysis supports the wurtzite hexagonal crystal structure and the average crystallite size reduced from 37 nm to 26 nm with the increasing Ni doping in ZnO. The progression from undoped ZnO (NiZ-0) to 3 % Ni-doped ZnO (NiZ-3) demonstrates a clear trend of morphological transition from elongated rods to granular particles. The EDS analysis was used to study the elemental analysis of Ni-doped ZnO. The values of energy bandgap were determined to be 3.30 eV, 3.29 eV, 3.26 eV and 3.24 eV for the Ni-doped ZnO films, with doping concentrations of 0, 1, 2, and 3 %, respectively. Photoluminescence analysis confirmed the formation of defects. The gas sensing investigation of acetone vapours indicates that the Ni-doped ZnO sample exhibited superior gas sensing response at 150 °C temperature compared to the other samples. The maximum response of the 3 % Ni-doped ZnO sensor is 83.11 %, with rapid response and recovery times at 25 ppm of acetone vapours.