Effect of Mg doping on structural, optical and photocatalytic activity of SnO₂ nanostructure thin films

In the present work, magnesium (Mg) doped SnO₂ nanocrystalline thin films were synthesized by simple chemical bath deposition technique. The as-deposited films were annealed at 600 °C for 5 h in ambient atmosphere in order to improve crystallinity and structural perfection. The influence of Mg doping on structural, optical, and morphology of 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 has been found to decrease with the increase of the dopant concentration as investigated by atomic force microscopy. The optical band gap energy of pure SnO₂ has been found to be in the range of 3.63 eV and it is shifted to 3.42 eV for 10 wt% Mg doping. In the Raman spectrum, two active mode (A_2u and E_u) were observed for Mg–SnO₂ thin films. The photocatalytic activities of the films were evaluated by degradation of methylene blue rhodamine B in an aqueous solution under ultraviolet light irradiation. The photocatalytic activity of Mg (10 wt%) doped SnO₂ film was much higher than that of the pure SnO₂. The samples were further characterized by photoluminescence spectra analysis.