MoO$_{3}$:In$_{2}$O$_{3}$ binary oxide thin films as CO gas sensor

Thin films of binary oxides (MoO$_{3}$-In$_{2}$O$_{3}$) of different normality proportions of 0.1N:0.1N, 0.2N:0.1N, 0.3N:0.1N, 0.1N:0.2N, 0.2N:0.2N, 0.3N:0.2N, 0.1N:0.3N, 0.2N:0.3N and 0.3N:0.3N were prepared by a spray pyrolysis technique on glass substrates at 400$^{\circ}$C. The prepared films were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive analysis by x-ray spectra (EDAX). The electrical and gas sensing properties of the films were studied using static gas sensing apparatus. The electrical analysis confirmed that the resistivity of films increased by adding MoO$_{3}$ as the dopant in In$_{2}$O$_{3}$. The maximum resistivity of film was found 1.75$\times$ 10$^{4}$ $\Omega$m for 0.3N (MoO$_{3}$) and 0.1N (In$_{2}$O$_{3}$) binary oxide films. The films were tested against five different target gases. The composition ratio 0.3N:0.1N films showed the 70.50% sensitivity for 300 ppm CO gas at 150$^{\circ}$C. The response time (15 s) and recovery time (25 s) was found to be quick. The % selectivity was maximum for 0.3N:0.1N films.