Z.El-Gohary
,
M.El-Nahass
,
H.Soliman
,
Y.L.El-Kady
材料科学技术（英文）
The different optical dispersion parameters of SrLaAlO4 single crystals have been studied by the transmission and reflection measurements at normal incidence for the three orientations 001, 100 and 101 in the spectral range 400nm-2500nm.The optical absorption data revealed the existance of allowed indirect and direct transition. The refractive index has abnormal behaviour in the spectral region 400-900nm, but has a normal one in the higher wavelength region. The optical dispersion parameters, the single oscillator energy Eo and the dispersion energy Ed were determined and indicated the ionic structure of the material. The high-frequency dielectric constant, the lattice dielectric constant and the electronic polarizability were determined by the free carriers and the lattice vibration modes. The real dielectric constant ε1 the dielectric loss tangent (tanδ), the volume (VELF) and the surface energy loss function (SELF) have also been discussed.
关键词:
Optical parameters
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Z.El-Gohary
,
A.Abdel-Aal
,
A.Elshafie
材料科学技术（英文）
Several thin films of Te10Ge10Se77Sb3 chalcogenide glass of different thicknesses (250nm to 400nm) were prepared by thermal evaporation under vacuum of 133 ×10-6 Pa(10-6torr). X- ray diffraction analysis showed the amorphicity of the prepared films which become partially crystalline by annealing. Transmittance and reflectance measurements in the spectral range of 200nm to 2500nm have been carried out at normal incidence. The analysis of the absorption coefficient data showed the existence of indirect transition for the photon energy E in the range 1-3eV and direct transition for E>3eV. From the determination of the optical constants (n, k), the dispersion of the refractive index has anomalous behaviour in the region of the fundamental absorption edge, and followed by the single- effective oscillator approach.The investigated optical parameters such as the optical energy gap Eopt, the high frequency dielectric constant eoo ,the oscillator position lo, and the oscillator strength So, were significantly affected by the film thickness. The characteristic energy gap obtained from the conductivity measurements is nearly half the value of that obtained from the optical data as in the case of thickness 400nm. The activation energy is 0.65 eV and the indirect optical gap is 1.32eV.
关键词:
Chalcogenide glasses
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null
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