Influence of Cu doping on structural, optical and photocatalytic activity of SnO₂ nanostructure thin films

This paper describes the pure and copper doped SnO₂ nanocrystalline thin films with large specific surface areas fabricated on a desired substrate using a simple chemical bath deposition technique. The as-deposited films were annealed at 500 °C for 2 h in ambient atmosphere in order to improve the crystallinity and structural perfection. The influence of Cu doping on structural, optical, and surface topography of the thin films was studied by X-ray diffraction (XRD), Raman spectra, UV–Vis spectra, photoluminescence, and atomic force micrograph images. The XRD measurements showed that films had a tetragonal rutile type structure with P42/mnm symmetry and the results were good in agreement with the standard JCPDS data (card no: 41-1445). The surface roughness and porosity has been found to decrease with the increase of the dopant concentration as investigated by atomic force microscopy. The characteristic Raman peaks observed at 325, 466, 672 and 745 cm⁻¹ were respectively revealed infrared active (E_u), Raman active (E_g), (A_1g) and (B_2g) vibration modes of pure tetragonal rutile SnO₂ structure. The optical band gap energy of pure SnO₂ has been found to be in the range of 3.68 eV and it is shifted to 3.32 eV for 10 wt% Cu doping. The photocatalytic activities of the films were evaluated by the degradation of methylene blue rhodamine B in an aqueous solution under ultraviolet light irradiation. The photocatalytic activity and reusability of Cu (10 wt%) doped SnO₂ film was much higher than that of the pure SnO₂.