Influence of thickness on optical properties of a-(Se₈₀Te ₂₀)₉₆Ag₄ thin films

Bulk sample of (Se₈₀Te₂₀)₉₆Ag₄ was prepared by quenching technique. Thin films of (Se₈₀Te ₂₀)₉₆Ag₄ glasses of different thickness (500-950 nm) were deposited on dry clean glass substrates by thermal evaporation technique. Energy dispersive X-ray spectroscopy (EDX) indicates that samples are nearly stoichiometric. X-ray diffraction patterns indicate that they are in the amorphous state. The optical constants, refractive index, absorption index, and optical band gap have been calculated from transmittance and reflectance data in spectral range of 400-2500 nm. It has been found that the optical band gap decreases, but the refractive index, extinction coefficient, optical conductivity, real and imaginary dielectric constant increase with increase in thickness of (Se₈₀Te₂₀)₉₆Ag₄ thin films. The results are discussed on the basis of rearrangements of defects and disorders in the chalcogenide systems.