High sensitive room temperature NH3 gas sensing properties of Bi-doped In2O3 thin films coated by nebulizer spray pyrolysis method

Developing a rapid, convenient, accurate and room temperature detection of the toxic or harmful gases which directly affects people's lives is an urgent requirement to protect living beings especially humans. With this purpose, present meticulous study aims on preparing transition metal ion of Bi³⁺ doped indium oxide (In₂O₃) thin films containing different amount of Bi (0, 1, 2, 3, 4, and 5 wt %) by executing nebulizer spray pyrolysis technique as a future room temperature ammonia gas sensor. All the formed films are found in cubic phase and display a strong orientation along (222) plane. The In₂O₃ film doped with 2wt% of Bi exhibited maximum values in terms of crystallite size (54 nm) and unit cell volume (1003.67 ų). The FESEM images of all the investigated films indicate the appearance of fine grains. Modest reduction in the bandgap from 3.25 to 3.10 eV is observed along with the increase in the Bi-doping concentration. Presence of various defect states at 418, 480, 524 nm and enhancement of photoluminescence is seen by room temperature photoluminescence measurements. All the coated films are used as chemiresistive gas sensors by testing ammonia response at room temperature. Noticeably, In₂O₃ thin film having 2 wt% Bi showed an excellent ammonia response (130 with concentration of 150 ppm), short response/recovery time (4.31s/3.8 s), and remarkable selectivity than that of bare In₂O₃. We believe that these results can provide an appropriate solution for public safety as well as for industrial purpose.