Effect of annealing on the optical properties of Ag33Sb31Se36 thin films

Ag33Sb31Se36, thin films were prepared by thermal evaporation technique on glass substrates. X-ray diffraction analysis fur the as-deposited films sho wed that they have amorphous structure. On annealing at 200 degreesC films have a polycrystalline structure. The optical constants n and k of the as-d eposited and annealed films have been calculated from optical transmittance and reflectance data in the wavelength range 400-1500 nm using Murmann's e quations. Both n and k are practically independent on the film thickness in the range 182-478 nm. Analysis of the refractive index n yields a low freq uency dielectric constant, The optical transitions are found to be allowed indirect for the as-deposited and annealed films, and the corresponding ene rgy gaps increase with increasing annealing temperature. (C) 2001 Elsevier Science B.V. All rights reserved.