Tuning the nonlinear susceptibility and linear parameters upon annealing Ag60−xSe40Tex nanostructured films for nonlinear and photonic applications

Abstract

The current study focuses on the annealing-induced changes in the structural, non-linear/linear optical, and surface morphological characteristics of nanostructured Ag_60−xSe₄₀Te_x (x = 0, 5, 10, and 15%) films. The increase in crystallinity with annealing at 150 °C and 200 °C signifies the structural modifications in films, as observed by XRD and Raman analyses. Lattice shifting with Te doping was also investigated by high-resolution transmission electron microscopy. The changes in the size and surface morphology of particles were verified by field emission scanning electron microscopy. The compositional confirmation and agglomeration of particles in the prepared film were checked via energy-dispersive X-ray spectroscopy. Te doping in the film was also confirmed by X-ray photoelectron spectroscopy. The reduction in the optical bandgap and increase in the Urbach energy of the films upon annealing were calculated from the UV-visible data. The increase in the refractive index with the annealing temperature modified the other linear parameters such as oscillator energy, volume, and surface energy loss function. The skin depth decreased and the extinction coefficient increased with annealing. The increase in the optical density value is good for the film to be used as a solar cell absorbing layer. The increase in the non-linear optical properties, such as the first- and third-order susceptibility, and non-linear refractive index, upon annealing is useful for nonlinear optical and photonic applications.