Impact of silver/copper dual-doping on the structure, linear and non-linear optical performance of ZnO thin films

The impact of Ag, Cu and Ag/Cu dual-doping on the structure, linear and non-linear optical performance of ZnO thin films has been investigated. Undoped ZnO and Ag, Cu and Ag/Cu dual-doped ZnO thin films (Zn 0.95 Ag 0.05− x Cu x O, where x : 0, 0.025 and 0.05) were prepared using the spray pyrolysis method. The morphology of the samples was examined using a scanning electron microscope. The variations in the samples’ structure were explored using a Fourier transform infrared spectrophotometer. The optical transmittance and absorbance spectra were measured using a UV–visible-NIR spectrophotometer. The optical properties analysis reveals that the absorbance of the doped ZnO thin films increases due to Ag, Cu and Ag/Cu dual doping. While the energy bandgap of the plain ZnO decreases from 3.27 to 3.12 eV (Ag-doped ZnO), 3.02 eV (Ag/Cu dual-doped ZnO) and 2.95 eV (Cu-doped ZnO). The refractive index (n), dielectric constants and nonlinear optical properties of the ZnO thin film are greatly enhanced due to Ag, Cu and Ag/Cu dual doping. For instance, at the incident photons energy of 2.5 eV, n increases from 2.06 (plain ZnO) to 2.28 (Ag-doped ZnO), 2.45 (Ag/Cu dual-doped ZnO) and 2.90 (Cu-doped ZnO). The third-order nonlinear optical susceptibility ( χ (3) ) is improved from 8 × 10 –13 esu (plain ZnO) to 2.1 × 10 –12 esu (Ag-doped ZnO), 4.13 × 10 –12 esu (Ag/Cu dual-doped ZnO) and 2.05 × 10 –11 esu (Cu-doped ZnO).The enhanced linear and nonlinear optical properties of the ZnO thin films via Ag, Cu and Ag/Cu dual-doping nominate them for optical and photonic applications.