Optical Properties Study in As_(50)Se_(50) and As_(50)Se_(40)Te_(10) Chalcogenide Thin Films.

摘要

Amorphous As_(50)Se_(50) and As_(50)Se_(40)Te_(10) thin films were prepared by thermal evaporation technique. The amorphous nature of these films were confirmed from the XRD study. The optical transmission spectra of these films were measured in the wavelength range of 400-1200 nm. The transmittance power is found to be decreased with Te incorporation into As_(50)Se_(50) while the absorption value is increased. The mechanism of the optical absorption follows the rule of allowed non-direct transition. The optical band gap value is found to be decreased while the width of localized states (urbach energy) E_e increases with Te addition. Addition of Te into As_(50)Se_(50) is found to affect the refractive index and extinction coefficient. The Raman shift observed in the two films clearly supports the optical changes due to Te addition. The chemical bond approach has been applied to interpret the decrease in optical band gap.