In2S3-Gr and In2S3-CNT nanocomposite thin films as gas sensors

The present work reports the response of the In2S3-Gr and In2S3-CNT nanocomposite thin film sensors in the presence of interfering vapours such as alcohols like ethanol and methanol, ketone like acetone and inorganic gas like ammonia. We also investigated the variation in gas sensing properties with change in thickness of the nanocomposite thin films. The structural, topological, compositional and optical analysis of samples are performed using X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and UV–Vis-NIR spectroscopy. The lattice strain, the crystallite size and dislocation density of as-deposited films were obtained from XRD analysis. The thickness of the films and surface roughness are determined by AFM analysis. The XPS depth profile affirms the presence of In, S, C and O in all the samples. From optical absorption studies, bandgap was determined and this is compared with thickness of the films. As the thickness increases, the bandgap energy of the In2S3-Gr/In2S3-CNT nanocomposite thin film decreases from 2.52/2.75 eV to 2.05/2.42 eV. The gas sensing parameters such as sensitivity, response time and recovery time of all the samples are determined. From the experiment, it is obtained that the triple dip In2S3-Gr nanocomposite thin film with the highest root mean square roughness and the lowest bandgap energy shows the highest gas sensing efficiency and have better sensitivity to ethanol vapour.