Tuning the energy bandgap and nonlinear absorption coefficients of CdO nanocomposite films with doping and annealing process

Abstract

The effects of doping and annealing on the linear and nonlinear optical properties of CdO, CdO:Cr and CdO:Sb nanocomposite films are investigated. The nanoparticles were synthesized with hydrothermal method. Their films were obtained by spin coating method. The XRD measurements exhibited that all synthesis nanoparticles are in cubic structure. The crystallite sizes of the CdO nanoparticles were decreased from 20.1 nm to 18.1 nm with the incorporation of the Cr and Sb dopant to the crystal lattice while the crystallite sizes were increased with post annealing. The band gap energies were found to be 5.37 eV and 5.31 eV for CdO:Cr and CdO:Sb nanoparticles which are higher than that of undoped CdO (5.11 eV). The band gap energies of the as-grown nanoparticles were decreased with annealing due to the increasing crystallite size of the synthesis nanoparticles. The transmittance of CdO increased with Cr and Sb doping and showed sharp rise near the band edge. In order to investigate the nonlinear absorption characteristics, the open aperture Z-scan experiments were performed by using 4 ns pulse laser. The absorption coefficeients and saturation intensity threshold increased with doping and decreased with post annealing.