Insight on the optoelectronic properties of novel quaternary Ge–Se–Tl–Sb non-crystalline glassy alloy films for optical fiber sensing devices

Chalcogenide glass (Ge 0.1 Se 0.7 Tl 0.2 ) 85 Sb 15 is synthesized in bulk form by the melt quenching method and thermally evaporated as thin films. The amorphous character of the studied films is examined by XRD analysis. The values of refractive index ( n n ) and extinction index ( k k ) are estimated from transmittance T(λ ) T ( λ ) data using Swanepoel’s method and are found to be thickness independent. The values of the indirect optical band gap ( Eg^opt E g opt ) and Urbach tail ( E_U E U ) energies are 1.164 eV and 0.176 eV, respectively. The optical σ _opt σ opt and electrical σ _elec σ elec conductivities of (Ge 0.1 Se 0.7 Tl 0.2 ) 85 Sb 15 films increase while the penetration depth P_d P d decreases with photon energy ( hν h ν ). The Wemple-DiDomenico (WDD) oscillator model calculates optical parameters such as single-oscillator E_o E o and strength E_d E d energies, lattice dielectric constant ε _L ε L and ratio N/m* N / m ∗ . The calculated values of third-order susceptibility χ ⁽³⁾ χ ( 3 ) and nonlinear index of refraction n₂ n 2 are 6.34 × 10 –12 and 3.76 × 10 –11 esu esu . Dielectric constant ε ^ ε ′ and loss ε ^ ε ′ ′ decrement with frequency and increment with temperature. The ac conductivity σ _ac σ ac increases with frequency and temperature, which is proportional to ω ˢ ω s and the exponent s s decreases with temperature. The obtained results of σ _ac σ ac and s s are interpreted via the correlated barrier hopping (CBH) model. Values of the density of localized states N(E_F) N E F are enhanced with frequency and temperature. The results obtained suggest that ε ^ ε ′ , ε ^ ε ′ ′ , σ _ac σ ac and N(E_F) N E F are improved by decreasing the film thickness. These research results emphasize the composition’s applicability for several optical potential applications, like optical fiber sensing devices, photo-detectors, and narrow band optical filters.