Composition dependence of the optical constants of amorphous (Se₈₀Te₂₀)_100−xAg_x (0 ≤ x ≤ 4) films

Abstract

This paper reports the influence of silver (Ag) addition on the optical constants of chalcogenide (Se 80 Te 20 ) 100Àx Ag x (0 x 4) thin films. Films of (Se 80 Te 20 ) 100Àx Ag x (0 x 4) glasses were prepared by thermal evaporation of the bulk samples. The transmittance and reflection spectra of amorphous thin films were obtained in the spectral region in the range 400-2500 nm. The optical band gap and the absorption coefficient were calculated from the transmission and reflection data. Swanepoel method has been applied to derive the real and imaginary parts of the complex index of refraction, refractive index, and also the thickness of amorphous films. The dispersion parameters are calculated by using the WempleDiDomenico model. The optical constants, i.e., the refractive index, extinction coefficient, absorption coefficient, and optical band gap are determined and their compositional dependence is considered. The results are discussed on the basis of defects and disorders present in chalcogenide systems.

Doping impacts of La2O3 on physical, structural, optical and radiation shielding properties of (30-x)BaCO3–30TiO2–40SiO2-xLa2O3 (0 ≤ x ≤ 6) glasses for optoelectronic applications

“…Based on Herzfeld theory Komatsu and Dimitrov have predicted the nature of solid or condensed materials that if R m /V m < 1 then the solids behave like a non-metallic material, if R m /V m > 1 then the solids behave like a metal, and if R m /V m = 1 (i.e., 100% reflection loss) then the refractive index becomes of infinite order. The comparatively larger value of M c explained that the separation (width) of the CB and VB are large due to this probability, little bit of broad band-gap was generated and enhances the nonmetallic or insulating behaviour of the glassy materials [47,72,73]. Herein, the obtained values of M c were found to be less than one so the fabricated glasses are non-metallic or insulator in nature [47,73].…”

“…It is probably due to creation of NBOs which form more ionic bonds and manifest themselves in a large polarizability that leads to rise in the values of η. Also due to alteration in stoichiometry of glass batches and produced internal strain of the glassy material, the refractive index increases significantly [71,72]. Eventually, the values of optical dielectric constant, ε (table 2) were obtained for all prepared glass samples using an equation (24) and demonstrated in figure 9.…”

“…However, the capability to attract electrons to itself inside a molecule describes the electronegativity (χ). Pauling suggested that when two or more than two atoms having different values of χ then form an alloy or a compound, then a higher χ element attracts an e-pair towards itself more and acts like an anion while other elements act like a cation [72,73]. The values of χ were obtained in decreasing behaviour 1.054, 1.035, 1.024, and 1.013 respectively and this behaviour was due to the χ value of all components available in the glassy matrix.…”