Fabrication of Al and La co-doped CdS thin film for ammonia gas-sensing application through low-cost nebulizer spray pyrolysis technique

By employing a nebulizer spray pyrolysis approach, thin films of CdS, Al, La, and Al-La co-doped CdS thin films have been effectively formed on glass substrates, and their physical characteristics have been examined. The structural investigations confirmed the hexagonal structure of CdS with a preference for orientation along the (1 0 1) plane. The maximum crystallite size was observed for the Al-La co-doped CdS film compared to other prepared thin films. The granular structure was distributed uniformly for all the films according to FESEM data. To determine the optical characteristics with Al, La, and Al-La co-doping, transmittance was examined and found that the Al-La co-doped CdS thin film exhibit lower transparency due to enhanced light scattering. The energy band-gap value slightly decreased from 1.58 to 1.56 eV for the undoped and co-doped CdS films. The doping causes an enhancement of the emission peaks for doped and co-doped CdS films at ambient temperature, and the gas-sensing performance of both pristine and doped CdS thin films was examined for ammonia (NH${}_3$) gas. Doped CdS films were shown to be significantly more sensitive and a higher gas response (1390) to NH${}_3$ than pristine CdS thin film. The present study also showed that the co-doping of Al and La with CdS exhibited a faster response and recovery time of (42/21 s) during NH${}_3$ gas detection.