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Some Optical Investigations Thin Films of Ga80-xSexTe20 (where x=15% and 20%) Chalcogenide glass |
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PP: 179-185 |
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doi:10.18576/ijtfst/110204
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Author(s) |
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Khadijah M. AL. Mokhtar,
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Abstract |
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| Thin films of Ga80-xSexTe20. Chalcogenide glass with thickness (x = 15 and 20) were deposited on a chemically cleaned glass surface by thermal evaporation technique. The absorption spectra of the prepared samples were studied using spectrophotometers in the wavelength range 200-2500 nm. The optical parameters like absorption coefficient (α), extinction coefficient (k) and the optical bandgap (Eg) is calculated for the system. Ga80-xSexTe20.glassy the optical energy gap, is the result of both direct and indirect permissible transformations. Eg decreased from 2.237eV to 2.137eV when the transition is direct and from 1.114569 to1.05984 ev for indirect transition by increasing Se content. While the band tail width energy give the opposite trends For all samples, the reduction coefficient (k) is lowered by the wavelength ( λ). The absorption coefficient (α) was found to increase with the incident photon energy (hν) for both concentrations. Also, it is noted that both k and α increases with increasing Se concentration in a-Ga80-xSexTe20.glassy system. The reduction in optical band gap with increase in Se concentration may be attributed to an increase in the amount of disorder in the materials and increase in the density of defect states. Other optical parameters have been evaluated such as Dispersion energy, “Ed”, single oscillator energy, “E0”, and static refractive index, “n”, have been calculated According to the mode Wemple–DiDomenico model. Also, other parameters have been calculated such dielectric constant at infinite wavelength ɛ∞, lattice dielectric constant ɛl, concentration of the charge carriers per effective mass N/m*, N concentration of the charge carriers. Due to the large absorption coefficient and component reliance on absorption, these materials may be appropriate for optical devices. |
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