Effect of Ce doping on MoO3 thin films for room temperature ammonia sensing application

In this work, we report the fabrication and gas sensing application of undoped, and Ce doped (1, 2, 3, 4, 5 wt%) MoO3 thin films via simple, effective, and low-cost nebulizer spray pyrolysis method. The crystal structure of the prepared thin films was found to be monoclinic by the prominent peaks observed at (001), (002) planes and the primary peak intensities increases from undoped to 3% Ce doped MoO3 thin film. The morphology of the samples was studied by FESEM, and the films have nanofibrous network embedded with nanorods spread over the surface of the nanofibers. The optical properties were characterised by the UV-vis spectroscopy and observed that the film's energy band gap declines from 3.28 to 3.04 eV due to the Ce dopant which alters the energy levels of the conduction and valence bands of the host by oxygen defects. The defects were analysed by the PL spectroscopy, and it proved that the PL emission peaks arose due to the oxygen deficiencies. The 3% Ce doped MoO3 produced higher PL emission intensity indicated that the higher oxygen defects sites are the cause. The gas sensing responses were measured for the pristine and 1, 2, 3, 4 and 5 wt% Ce doped MoO3 gas sensors increase from 6.48 x 10(2) to 1.67 x 10(4) and found to be higher for the 3% Ce doped sensor to detect ammonia gas. The significant gas sensing property such as rise time and fall time were observed to be least for the 3% Ce doped MoO3 thin film was 54 and 5 s. This study revealed that 3% Ce doped MoO3 thin film could be an efficient prominent ammonia gas sensor at room temperature in future.