Optimized CO2 Gas Sensing with SnS:Sm2O3/n-Si Nanocomposites Fabricated via Spray Pyrolysis

In this work, tin sulfide:samarium oxide (SnS:Sm2O3) composite films were deposited using a spray pyrolysis technique for room-temperature CO2 gas sensing. X-ray diffraction (XRD) confirmed a polycrystalline SnS nature of orthorhombic-phase crystallinity at 10 at.% Sm ions, while 20 at.% Sm induced Sm2O3 as a separate phase. Field emission-scanning electron microscopy (FE-SEM) induced uniform grains and increased the surface roughness, enhancing gas adsorption. UV-visible absorbance revealed band-gap narrowing. Fourier transform infrared spectroscopy (FTIR) analysis revealed vibrational band shifts, confirming the structural modifications. Gas-sensing measurements demonstrated 5.72%, 19.65%, and 9.65% for pure SnS, 10 at.% and 20 at.% Sm films sensitivity values, respectively, against 500 ppm CO2 at room temperature. The minimum response and recovery times were 11 s and 13 s, respectively, for the same sample. These results demonstrate that SnS:Sm2O3 composite films prepared by a simple spray pyrolysis method present a simple and practical method for a room-temperature CO2 gas sensor with enhanced sensitivity and fast response dynamics, in contrast to pure SnS which shows low sensitivity toward CO2.