Optical properties of polyvinyl alcohol doped (Se80Te20)100–xAgx (0 ≤ x ≤ 4) composites

Abstract

Polyvinyl alcohol (PVA) doped (Se80Te20)100–xAgx (0 ≤ x ≤ 4) thin films were prepared by the spin-coating technique on a quartz substrate. The optical parameters of PVA-doped (Se80Te20)100–xAgx (0 ≤ x ≤ 4) composites at the same chalcogen concentration (S0 = 0.1 mg ml−1) and PVA/(Se80Te20)96Ag4 composites at three different chalcogen concentrations viz. S1 = 0.3 mg ml−1, S2 = 0.6 mg ml−1 and S3 = 1 mg ml−1 have been studied. The semi-crystalline nature of the as-deposited thin filmsisdetermined by X-ray diffraction. The transmission and reflection spectra of PVA-doped Se–Te–Ag thin films were obtained in a 350–650 nm spectral region. The optical-band gap has been calculated from the transmission and reflection data. The refractive index has been calculated by the measured reflection data. It has been found that the optical-band gap increases, but the refractive index, extinction coefficient, and the real and imaginary parts of the dielectric constant decrease, with increase in Agcontent in PVA-doped (Se80Te20)100–xAgx (0 ≤ x ≤ 4) thin films. Such type of behavior is explained on the basis of decrease in density of the defect states. However, the optical-band gap has been found to be decreased and all other optical parameters show increase in their values with increase in concentration of (Se80Te20)96Ag4 glass in PVA-doped composites. The results have been explained on the basis of cluster-size formation at the time of dissolution. This study shows that the optical properties of new composites are affected by the change in silver and chalcogen concentration.