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Determination of Optical Band Gap and Optical Constants of GexSb40-xSe60 Thin Films |
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PP: 179-185 |
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Author(s) |
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M. M. Hafiz,
N.El-Kabany,
H. Mahfoz Kotb,
Y. M. Bakier,
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Abstract |
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| GexSb40-xSe60 (where 10≤ x≤ 30 at %) thin films were prepared on glass substrates by thermal evaporation technique. X-ray diffraction analysis for as – deposited films showed that they have amorphous structure. The optical constants of the as- deposited films were calculated from optical transmittance and reflectance data in wavelength range from 400 to1200 nm. We found that both refractive index, n and extinction coefficient, k increased with increasing photon energy. Optical band gap was determined from absorption coefficient data using Tauc procedure and from the energetic distribution of the absorption coefficient. The optical absorption data indicate that the absorption mechanism is due to indirect transition. The optical gap of the as- deposited films was found to decrease monotonically with increasing Sb content , a result was interpreted on the basis of the chemical- bond approach. The dispersion of the refractive index is analyzed in terms of Wemple- DiDomenico single oscillator model. The optical dispersion parameters E0 and Ed were determined according to this model. The characteristic Urbachs parameters such as steepness parameter, σ and Urbachs energy have been determined. The real and imaginary parts of the dielectric constant in addition to the dissipation factor tan δ and the optical conductivity were also determined. |
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