Thickness effect on VOC sensing properties of sprayed InS films.

This work reports the thickness effect on the sensing performances of InS material for some Volatile Organic Compounds (VOCs). InS films were deposited on glass substrates by the spray pyrolysis technique. Different samples were prepared changing the spray time in the range of 10-90 min. The film thickness varies from 0.8 μm to 6.1 μm. The X-ray diffraction results demonstrate that the InS films are polycrystalline in nature and exhibit a cubic structure. Additionally, Scanning Electron Microscopy (SEM) and 3D profilometry examinations show that the surface roughness increases with the rising spray time. On the other hand, the oxygen adsorption working temperature was investigated. Sensing measurements with ethanol, methanol and acetone gases were carried out by a dynamic control of the current passing through the sensitive layers. The best sensitivity was obtained for the film matching a 70 min deposit time. An understanding of the detection mechanism based on the oxidation reaction between reduced vapors and chemisorbed oxygen was confirmed. The selectivity of the sensor was analyzed for several volatile organic compounds (VOCs).