الفهرس 
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Abstract
Our investigations show the following notable features: EDX analyses of Se70-xTexS30 (x= 10, 20 and 40 at. %) thin film show that the constituent element ratio of the investigated thin films is near to the nominal compositions. The X-ray diffraction indicate the amorphous structure of the as-deposited Se70-xTexS30 (x= 10, 20 at %), while the sample with (x= 40 at. %) is poly-crystalline in nature. The composition that we studied its thermal properties, namely Se50Te20S30 has one glass transition and single stage crystallization. The calculated activation energies of crystallization and the frequency factor indicate that the glass forming ability, (GFA) decreases with increasing heating rate. A good agreement between the experimental and calculated data is evident using the Sestak-Berggren, (SB) model, while a deviation is noticed of the calculated data when using the JMA model. The average particle size of the dominant crystalline phase Se30Te40S30 increases with increasing the annealing temperature. The properties of high transmittance in IR region make the film good materials for thermal control window coatings. The studied films have the property of screening off UV portion of the electromagnetic radiation by absorbing and for this reason these films use in eye glasses coating. The refractive index (n) decrease with increasing wavelength of the incident photon, while at higher wavelengths n tends to be constant for all compositions. On the other hand, n increase with increasing Te content, further increasing in the Te content, n increases. The optical absorption measurements for the asdeposited films indicate that the absorption mechanism is due to the allowed indirect transition. The optical energy gap (Eg) for the as-deposited Se70- xTexS30 (x= 10, 20 and 40 at. %) thin films decreases with increasing Te content. For the different thickness for Se30Te40S30 film it was found that Eg decreased. On the other hand, the width of the localized states (Ee) has opposite trend with Te content and for the different thickness of Se30Te40S30 composition. The band gap, Eg, decreases with increasing Te content shows its capability to be used as an absorber layer in photovoltaic application. The values of extinction coefficient (k) decrease with increasing the wavelength and become very small at longer wavelengths demonstrating that the films under test are highly transparent. The decreasing of extinction coefficient with wavelength shows that material is getting transparent with wavelength, which makes it useful optical material in high wavelength range. The single oscillator energy, E0 decreased with increasing of thickness, annealing temperature and Te content. The dispersion energy, Ed behaves differently behavior of the single oscillator energy The electrical conductivity results can be summarized as following: For different annealing temperature of Se30Te40S30 thin films, there are two types of conduction channels contribute two conduction mechanisms. The electrical conductivity increased and the activation energy for conduction (ΔE) decreased with increasing of annealing temperature. For Se50Te20S30, analysis of the electrical conductivity results revealed two types of conduction mechanisms: conduction due to extended states in the temperature range T > Tc and variable range hopping in the temperature range T < Tc. The results indicate the decrease of ∆E of conduction with increasing the thickness of thin film. It is also noted that the electrical resistivity, ρ decreases with increasing film thickness. For Se70-xTexS30 (x=10, 20 and 40 at.%) thin films, the temperature dependence of the DC conductivity through the temperature range 300–500 K, suggest that there are two types of conduction channels that contribute to the conductivity, the values of the activation energy, ΔE, decreases with increasing Te content and the electrical conductivity increases.