Role of Zn in tuning the band gap, surface morphology, photoluminescence and optical nonlinearities of CdO nanostructures for photonic device applications

We report the role of Zn doping on third-order nonlinear optical properties (NLO) of CdO thin films. Thin Cd_1-xZn_xO'films' was prepared using the spray pyrolysis (SP) technique [with x = 0, 0.01, 0.05 and 0.1 at. %] to study the morphological, surface morphology, linear optical, photoluminescence and NLO properties. The study of x-ray diffraction (XRD) revealed the crystalline nature of the prepared thin films, and the Zn-doping improves the crystallite size. The' films morphology is mainly influenced by the'doping'shown by the images of FESEM (field emission scanning electron microscopy). As the doping concentration of Zn increases, the direct energy band-gap (Eg) value increased from 2.51 eV to 2.60 eV for undoped CdO to 10% of Zn doped CdO. Room temperature photoluminescence spectra (RTPL) of the prepared samples are investigated for an in-depth understanding of the conduction band behavior of defect states. Z-scan data showed strong'two-photon absorption'(2PA) for the deposited films and with an'increase in doping concentrations'from 0 to 10 (at %), the'nonlinear absorption coefficient (β) increasing from 1.22 ×10^-4 to 4.50 × 10^-4 (cmW^-1), nonlinear refractive index from 7.06 ×10^-9 to 1.30 ×10^-8 (cm²W^-1) and χ ⁽³⁾ i.e. third-order NLO susceptibility'values also increased from 4.03 ×10^-7 to 7.31 ×10^-7 (esu). Optical Limiting characteristics of the prepared films was studied at the experimental wavelength. The inspiring results of the NLO properties propose that Cd_1-xZn_xO thin film is an accomplished and promising material for'NLO'device applications.