Structural, optical, and electrical characteristics of Ge18Bi4Se78 chalcogenide glass for optoelectronic applications

The melt quenching and thermal evaporation techniques were used to produce the chalcogenide glass Ge₁₈Bi₄Se₇₈ powder and thin film samples, respectively. The as-deposited and annealed thin films at (180, 200, 300, 320 °C) are characterized by X-ray diffractometer and scanning electron microscopy. The Urbach tail energy E_u and the optical energy gap E_op are investigated. As well, the Swanepoel method revealed that the refractive index exhibited normal dispersion behavior. In addition, the single oscillator, dispersion energies, the lattice dielectric constant, ${\epsilon }_L$, plasma frequency, ${\omega }_p$, and optical conductivity, ${\sigma }_{op}$ were all examined. The electrical conductivity and the activation energies for as-deposited and annealed thin films were calculated. Whereas the J-E properties of the as-deposited and annealed films indicated varied ranges of negative differential conductance NDC depending on the annealing temperatures.