Abstract
The molybdenum trioxide (MoO3) thin films have been successfully deposited onto the glass substrates using chemical spray pyrolysis (CSP) deposition technique at various substrate temperatures ranging from 300°C to 450°C with an interval of 50°C. The effect of substrate temperature on the structural, morphological, optical and gas sensing properties of MoO3 thin films has been thoroughly investigated. X-ray diffraction analysis reveals that all the films have an orthorhombic crystal structure and are polycrystalline in nature. FE-SEM micrographs depict the formation of nanobelts-like morphology. AFM study reveals that the RMS surface roughness of MoO3 thin films increases from 8.6nm to 12nm with increase in substrate temperature from 300°C to 400°C and then decreases to 11.5nm for substrate temperature of 450°C. Optical results show that the band gap of MoO3 thin films decreases from 3.92eV to 3.44eV. The selectivity studies show that the gas response of various gases varies as NH3<SO2<CO2<CO<H2S<NO2. Moreover, typical MoO3 film deposited at substrate temperature of 400°C is highly selective and sensitive for detection of NO2 gas in comparison with other gases. The maximum response of 30.5 % is obtained towards 100ppm NO2 gas concentration at an operating temperature of 200°C with response and recovery times of 20s and 160s, respectively. Finally, NO2 gas sensing mechanism model based on the chemisorption process is discussed.
Published Version
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