Effect of annealing on the optical properties of Ag33Sb31Se36 thin ®lms

Ag33Sb31Se36 thin ®lms were prepared by thermal evaporation technique on glass substrates. X-ray diffraction analysis for the as-deposited ®lms showed that they have amorphous structure. On annealing at 2008C ®lms have a polycrystalline structure. The optical constants n and k of the as-deposited and annealed ®lms have been calculated from optical transmittance and re¯ectance data in the wavelength range 400±1500 nm using Murmannʹs equations. Both n and k are practically independent on the ®lm thickness in the range 182±478 nm. Analysis of the refractive index n yields a low frequency dielectric constant. The optical transitions are found to be allowed indirect for the as-deposited and annealed ®lms, and the corresponding energy gaps increase with increasing annealing temperature. # 2001 Elsevier Science B.V. All rights reserved.