Preparation of CuWO4 films by thermal annealing of simultaneously RF/DC magnetron co-sputtered Cu–W films

Tungstate-based compounds have garnered significant interest for applications in photocatalysis, optoelectronics, and energy-related technologies due to their distinctive structural, optical, and electronic properties. This study focuses on the synthesis, structural characterization, and optical properties of copper (II) tungstate (CuWO 4 ) thin films, produced via co-sputtering of metal precursors followed by thermal annealing in air at temperatures ranging from 450 to 650 °C. XRD and Vis-NIR spectroscopy confirmed that annealing at 600 °C yields CuWO 4 films with the highest crystallinity and the lowest indirect band gap of 2.09 eV. A comprehensive analysis of the films' surface morphology, phase composition, and chemical states was conducted using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results confirm the formation of highly crystalline CuWO 4 films with a triclinic structure. Additional structural insights were obtained from Raman and Fourier-transform infrared (FTIR) spectroscopy, which revealed vibrational modes associated with the WO 6 octahedral units. These films should be further explored for their potential applications in photocatalysis and photoelectrochemical cells.