الفهرس 
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Abstract
The present study is devoted to investigate the effect of Sb addition on the structure, optical and electrical properties (DC conductivity, AC conductivity and dielectric properties) of Se-Ge-Ga thin films.
A quenching technique was used to prepare the chalcogenide system of the Se_(60-x) Ge_35 Ga_5 Sb_x (x = 0, 5, and 10 at. %), which was deposited as thin films onto glass substrates using a thermal evaporation technique. X-ray diffraction patterns were used for structure examination of the fabricated compositions, which exposes the amorphous nature of the deposited samples. Meanwhile, the chemical compositions of the prepared samples were evaluated and calculated via the energy-dispersive X-ray spectroscopy (EDX), which was in agreement with the measured compositional element percentages of the prepared samples, differential scanning calorimeter DSC was used to calculate glass transition temperature T_g for the studied film compositions.
Based on the optical reflectance R and transmittance T spectra from the recorded spectrophotometric data ranging from 350 to 2500 nm, the influence of the Sb element on the Se_(60-x) Ge_35 Ga_5 Sb_x thin films’ optical properties was studied. The film thickness and the refractive index were calculated via Swanepoel’s technique from optical transmittance data. It has been observed that the films’ refractive index increases with increasing x value over the spectral range. The refractive index data were used to evaluate the dielectric constants and estimate dispersion parameters E_ₒ and E_d using the Wemple–DiDomenico model. The optical energy gap E_g^opt was calculated for the tested compositions. The result of the optical absorption analysis shows the presence of allowed direct and indirect transitions.
Dc conductivity σ_dc measurements of the investigated compositions in thin film form were carried out as a function of temperature in the range (303-433 K) for the thickness 350 nm. The dc conductivity of Se_(60-x) Ge_35 Ga_5 Sb_x (x = 0, 5, and 10 at. %) increases with increasing temperature as well as with Sb additives. The results indicated the presence of two different conduction mechanism in studying Se_60 Ge_35 Ga_5 while it became one conduction mechanism with Sb additive.
Ac conductivity and dielectric constant measurements were studied for the investigated compositions at different frequencies in the range (100 Hz – 1 MHz) and in the temperature range (303 – 403 K). The ac conductivity for all investigated compositions was temperature dependent. The dielectric constant and the dielectric loss was discussed as a function of frequency and temperature for the investigated compositions. The obtained results were explained on the basis of correlated barrier hopping [CBH] model.