Preparation and Study of the Effect of Annealing Temperature on the Structural, Optical, and Morphological Properties of Nanocrystalline SnO2 Doped with Cu

In this study, pure SnO2 nanocrystalline films were doped with copper using the spray pyrolysis technique. SnCl2.2H2O, CuCl2.2H2O were used as precursors. The preparation was done in the form of nanoparticles by chemical precipitation method. The prepared materials were annealed at 300°C and 500°C for 1 h to improve crystallization. XRD results of the samples prepared by spray pyrolysis of a solution containing nanoparticles showed that the samples were crystallized in the rutile tetragonal phase. The average crystal size of SnO2 annealed at 300°C is 3.36 and 3.37 nm for pure and doped samples, respectively, and it is 4.1 nm and 9.75 nm for pure and doped annealed at 500°C, respectively. It is noticed that the crystal structure of SnO2 does not change with the addition of copper, and the studies of Field Emission Scanning Electron Microscopy confirmed the results where the grain size was within the range (20-50) nm, and the thickness of the films obtained from this assay was in the range (0.9-1.15) µm, with the thickness of doped films at 500°C are higher than those at 300°C. The Atomic Force Microscopy results showed that the roughness rate of the pure films annealed at 300°C and 500°C is 7.99 and 17.4 nm, respectively, while roughness for doped annealed samples were 9.09 and 7.12 nm, respectively. The optical results obtained from UV-Vis analysis showed that the optical bandgap at 300°C for pure and doped samples was (3.40 and 2.8) eV, respectively, while it was (3.75 and 2.59) eV at 500°C for pure and doped samples, respectively. The transmittance decreases with increasing annealing temperature, because the absorbance increases. The extinction coefficient increases, while refractive index decreases with increasing annealing temperature. The absorbance was 0.94 and 1.17 for pure and doped samples at 300°C, and was 1.16 and 1.46 at 500°C.