Eur. Phys. J. Appl. Phys.
Volume 59, Number 1, July 2012
|Number of page(s)||7|
|Published online||11 July 2012|
Chemical bond approach to optical properties of some flash evaporated Se100−XSbX chalcogenide alloys
Department of Physics, University of Botswana, P/Bag UB-0022 Gaborone, Botswana
2 Department of Physics, University of Nairobi, PO Box 30197-00100 Nairobi, Kenya
3 African Materials Science and Engineering Network (AMSEN), a Carnegie IAS-RISE Network, UB-Node, P/Bag UB-0022, Gaborone, Botswana
a e-mail: email@example.com
Revised: 5 June 2012
Accepted: 6 June 2012
Published online: 11 July 2012
Amorphous thin films of Se100 − XSbX (X = 1, 5, 10, 15 and 20) were synthesized by flash evaporation of the premelt quenched bulk samples. The optical properties were investigated from spectrophotometric measurements in the UV-VIS-NIR spectral region using Swanepoel’s standard envelope method and related techniques. The optical band gap energy (Egopt) was evaluated from the Wemple-Didomenico (WDD) single oscillator model and Tauc’s extrapolation method in the region where the absorption coefficient, α ≥ 104 cm–1. The observed values of Egopt and oscillator energy Eo were found to decrease monotonously with increasing Sb additive. The complex dielectric constant (ε), Urbach energy (Eu), optical conductivity (σ), plasma frequency (ωp) and lattice dielectric constant (εL) were deduced for each alloy composition. The complex refractive index (n) fitted well to Sellmeier function which can allow extrapolation of n outside the measured spectral range. The observed changes in optical parameters with Sb content were explained on the basis of increased defect states and changes in cohesive energy indicators (average heat of atomization (Hs), mean coordination number 〈Z〉 and average single bond energy (Hs/〈Z〉).
© EDP Sciences, 2012
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