Linear and nonlinear optical investigations of Ge25Se75 thin films at different annealing temperatures

Ge25Se75 chalcogenide films have been prepared using thermal evaporation method. X-ray diffraction (XRD) analysis shows polycrystalline natureof the annealed Ge25Se75 chalcogenide films at 340 degrees C. The significant transmittance of Ge25Se75 films at 1000 nm suggested the using of this material as an effective color filters. The indirect transition is the adopted mechanism of the electron transition for the as-deposited and the annealed Ge25Se75 films. The optical band gap energy (Eg)was found to be increased as the annealing temperature increases. In the regime of the normal dispersion, the single oscillating energy(E0), the dispersion energy (Ed) values and the dielectric constant (epsilon infinity)for the as-prepared and annealed films were calculated. In the transparent region, the lattice dielectric constant (epsilon L) was found to be decreased as the annealing temperature increases. Moreover, the measurements of the nonlinear optical parameters of these films at different annealing temperatures verify the possible using of thischalcogenide glass as a promised candidate material for optical applications.