Effects of te substitution on optical and dielectric properties of Te-As-Ge-Se chalcogenide glasses

Quaternary TeₓAs₂₀Ge₁₅Se₆₅₋ₓ (TAGS) chalcogenide glasses of varying compositions, namely, x = 10, 15, 20, and 25 mol%, were prepared by using the melt quenching technique. X-ray diffraction patterns with wide, diffuse halos devoid of crystalline peaks demonstrate that all samples are amorphous. The experimental density varies from 5.18 g cm⁻³ to 5.35 g cm⁻³, and the molar volume varies from 15.83 cm³ mol⁻¹ to 16.68 cm³ mol⁻¹, which is indicative of structural expansion due to the substitution of larger Te atoms into the Se sites. At the same time, the packing density is reduced and the free volume is increased, which is indicative of reduced atomic packing efficiency and increased structural flexibility. Optical analysis reveals strong absorption in the UV and visible regions with coefficients in the range of ~ 10⁴–10⁵ cm⁻¹, characteristic of amorphous chalcogenide semiconductors. The increase in Te content results in a red shift in the absorption edge, band gap narrowing, and Urbach energy increase. Wemple-DiDomenico dispersion analysis indicates a reduction in oscillator energy and an increase in dispersion energy as the Te content increases. Refractive index increases from 1.18 to 1.34, while the optical oscillator strength increases from 7.46 to 12.34 (eV)². Dielectric parameters increase as the concentration of Te increases. Optical density increases and the skin depth decreases, proving the absorption of the electromagnetic field. Te has the effect of tuning the TAGS glasses for the development of IR photonic devices and sensors, IR waveguides, and IR fiber communication systems.