Influence of Cu and Ag doping on structure and optical properties of In2O3 thin film prepared by spray pyrolysis

Thin films of In 2 O 3 and In 2 O 3 doped with Ag + or Cu 2+ were assembled by spray pyrolysis from aqueous solution at 450 °C. The microstructure analysis and optical properties were investigated using XRD, SEM, EDX and UV–Vis. spectrophotometer. XRD analysis proved that Ag-doping greatly reduces the crystallites sizes of In 2 O 3 from 96 nm to 59 nm. However, Cu-doping has less pronounced effect on the crystallite sizes than that of Ag doping. The band gap energy of In 2 O 3 decreases with both Cu 2+ and Ag + doping. The change in lattice parameter of cubic In 2 O 3 with Cu and Ag substitutions is compatible with the ionic radius of the substituted ions, i.e. Ag-substitution increases the lattice parameter and Cu-substitution decreases the lattice parameter. The calculated direct band gap of bare In 2 O 3 film is 3.59 eV. Doping In 2 O 3 with Cu 2+ and Ag + decreases the band gap to 3.36 eV and 3.27 eV, respectively. Ag + substitution in place of In 3+ ion in In 2 O 3 cubic lattice causes negative strain value due to the shrinkage of the interplaner spacing of the unit cell. In contrary, replacing In 3+ cation with Cu 2+ cation expands interplaner distances of the crystallographic planes of In 2 O 3 lattice and causes positive strain value. The present work demonstrates the capability to assemble high quality doped – In 2 O 3 thin films by simple solution based spray pyrolysis.