Synthesis and Characterization of Sn-Doped CuO Thin Films for Gas Sensor Toward H₂S Gas Sensing

In this work, thin films of CuO doped with 3% SnCl₂ (0.97 g CuO-0.03 g SnCl₂) were deposited on glass substrates using a sol–gel spin coating technique. The deposited thin films were annealed in a muffle furnace at 400°C for 2 h. UV–visible spectroscopy, a two-probe setup, and x-ray diffraction were utilized to analyze the optical, electrical, and structural properties, respectively. The optical bandgap of the doped films was identified within the range of 3.7–3.83 eV. Electrical investigation performed by the two-probe setup revealed that the prepared samples were ohmic in nature. It was found that the resistivity of the samples varied from 11.86 Ω·m to 6.04 Ω·m as the thickness of films increased from 165 nm to 570 nm. The gas-sensing properties of the prepared films were assessed at different operational temperatures and for varying concentrations of hydrogen sulfide gas. From the obtained data, it was observed that SnCl₂-doped CuO thin films show excellent response toward H₂S gas at room temperature.