Characterization of CuO‐Doped SnO ₂ Thin Films Prepared by Sol–Gel and Dip‐Coating: A Multi‐Analytical Approach

ABSTRACT In the current work, we comprehensively studied focus‐doped (5%) SnO 2 thin films, using scanning electron microscopy (SEM), X‐ray diffraction (XRD), and X‐ray photoemission spectroscopy (XPS). The films were synthesized via a sol–gel process followed by a dip‐coating deposition technique to form three‐layered structures. To understand the impact of annealing on the properties of the films, we analyzed samples both without annealing and with annealing at 400°C. Electron backscattering (BS) images revealed distinct differences in surface structures between annealed and non‐annealed films. The annealed films exhibited a more uniform and smooth surface with fewer defects, while the non‐annealed films showed a network of cracks and delaminations. XRD analysis of the annealed films indicated the formation of SnO 2 nanoparticles with an average size of 9 ± 1 nm, verifying the crystallinity and nanometric size of the material with heat treatment. XPS depth profiling demonstrated the presence of a metallic tin (Sn 0 ) layer at the interface of the films. The surface tin film was in mixed oxidation states, involving both Sn 4+ and Sn 2+ . Additionally, the copper within the films was found to exist as Cu 2+ and Cu + .