Facile Synthesis of High-Quality Cu–Cd–Mg Spinel Chromite Thin Film for Enhanced Ultraviolet Photodetectors

In this study, the Cu_0.4Cd_0.3Mg_0.3Cr₂O₄ spinel chromite compound was prepared through the sol–gel synthesis technique, and its structural, elastic, and optical behaviors were thoroughly investigated. X-ray diffraction analysis (XRD) verified the successful formation of a pure cubic spinel phase, while Fourier-transform infrared (FTIR) spectra exhibited distinct vibration bands associated with metal–oxygen bonds at the tetrahedral and octahedral coordination sites within the lattice. The calculated elastic constants indicated a brittle mechanical behavior with isotropic elastic characteristics. Optical investigations exhibited broad UV–Vis absorption bands with a direct optical band gap of 2.23 eV and a low Urbach energy of 0.91 eV, suggesting minimal structural disorder. A thin film of Cu_0.4Cd_0.3Mg_0.3Cr₂O₄ fabricated via spin coating displayed remarkable UV photodetection performance. Electrical measurements revealed a pronounced photocurrent enhancement under UV illumination, with rapid response times of 0.85 s (rise) and 1.36 s (decay) at a bias voltage of 1 V. Furthermore, the device exhibited a detectivity (D*) of 5.86 × 10¹⁰ Jones and a responsivity (R) of 11.78 A/W, comparable to high-performance UV photodetectors. The obtained results confirm the potential of Cu–Cd–Mg spinel oxide for efficient UV photodetection and optoelectronic technologies.