Time-Resolved Sensitivity of a Cadmium-Doped Copper Oxide Thin Film as a Chlorine Gas Detector

Due to its strong affinity for chlorine gas, Cd can potentially form CdCl 2 . Cd-doped CuO thin films are sensitive to chlorine gas, as careful inclusion of Cd in the CuO crystal structure modifies the energy gap depending on the dop - ant concentration. We employed spray pyrolysis to deposit Cd-doped CuO on fluorine tin oxide (FTO) while heat - ing the substrate to 500 °C. The X-ray diffraction (XRD) analysis revealed that Cd was interstitially incorporated in the CuO lattice structure, as verified by scanning electron microscopy (SEM) imaging. The photoluminescence study demonstrated that increasing the Cd concentration in CuO resulted in higher emission intensity, providing valuable insights into Cu 2+ and O 2-energy levels. Exposing a Cd-doped CuO thin film to chlorine gas modifies the bandgap, depending on the Cd concentration. The fluctuation in the bandgap energy of copper oxide doped with cadmium indicates the chlorine gas concentration nearby. Time-resolved measurements for the I-V characteristics of the thin film revealed considerable current variation during the exposure to chlorine gas.