Optical constants of new amorphous As–Ge–Se–Sb thin films

The present paper reports the effect of replacement of selenium by antimony on the optical constants of new quaternary chalcogenide As14Ge14Se72−xSbx (where x = 3, 6, 9, 12 and 15 at.%) thin films. Films of As14Ge14Se72−xSbx glasses were prepared by thermal evaporation of the bulk samples. The transmission spectra, T(λ), of the films at normal incidence were obtained in the spectral region from 400 to 2500 nm. A straightforward analysis proposed by Swanepoel, based on the use of the maxima and minima of the interference fringes, has been applied to derive the real and imaginary parts of the complex index of refraction and also the film thickness. Increasing antimony content is found to affect the refractive index and the extinction coefficient of the As14Ge14Se72−xSbx films. Optical absorption measurements show that the fundamental absorption edge is a function of composition. With increasing antimony content the refractive index increases while the optical band gap decreases.