Synthesis and enhanced room temperature ammonia gas-sensing properties of In-doped MoO₃ thin films prepared via nebulizer spray pyrolysis technique

For the application of room temperature ammonia gas sensing, different concentrations of 1, 2, 3, 4, and 5% of indium (In)-doped MoO3 thin films are synthesized using the nebulizer spray pyrolysis method. The various properties such as microstructure, morphology, and optical properties are characterized using several techniques, namely X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis spectroscopy, photoluminescence (PL) spectroscopy. The existence of orthorhombic crystal structure of MoO3 is confirmed through XRD analysis with variation in crystallinity with the incorporation of In dopants into MoO3. FESEM results showed the nanofibrous reticulated chained morphology for the as-fabricated MoO3 film, and the average diameter increased for the In-doped MoO3 films. The UV-Vis and PL studies revealed that the prepared 3% In-doped MoO3 film has lower transmittance, lower bandgap of 2.94 eV, and higher oxygen vacancies. Moreover, a maximum gas response of 18,900 for 3% In-doped MoO3 film was achieved while establishing the gas-sensing properties of the fabricated sensors for NH3 detection at ambient temperature. Faster response and recovery times of 42 and 8 s, respectively are seen at 3% In-doped MoO3 film sensor compared to the other fabricated sensors, which may be the useful candidate for sensitive application like MoO3 gas sensors.