الفهرس 
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Abstract
Summery
Bulk chalcogenide glassyalloys of Se80 Te20-x Inx (where x = 0, 4, 6, 8 and 12 at. %) were prepared by the melt-quenching technique. Thin films of these glasses were prepared by thermal evaporation under a vacuum of 10-5Torr. The amorphous nature of the prepared alloys and thin films was confirmed by x-ray diffraction measurements. The particle size and lattice strain were calculated for the prepared samples. The particle size was found to be in the range of nanoparticles.
The measurements of differential scanning calorimetry (DSC) under non-isothermal conditions were performed for the glassy alloys. The glass transition temperature (Tg), the onset crystallization temperature (Tc) and the peak temperature of crystallization (Tp) were found to be dependent on the composition and heating rates. The activation energy of glass transition (Et) and that for crystallization (Ec)were calculated. The reduced glass transition temperature was calculated for all prepared glassy alloys and it was found to obey the two – thirdsrule. The glass forming tendency was also calculated. The dependence of the glass transition temperature on heating rate was studied and it was found to obey Kissinger formulation.
The dc electrical conductivity was measured as a function of temperature. The temperature dependence of the dc conductivity was found to obey the Arrhenius relationship. The values of the activation energy and per-exponential factor were calculated. The validity of Meyer – Neldel rule was confirmed.
Electrical dielectric measurements were performed on the glassy alloys. Nyquist plots were used to represent the data between the real and imaginary parts of the impedance. The equivalent circuit could be represented by a bulk resistance (Rb)in parallel with a bulk capacitance (C) and these are in series with the surface resistance (Rs).The frequency and temperature dependence of the dielectric constant (ε`)for the prepared glassy alloys was measured. It was found that (ε`) decreases with increasing frequency and increase with increasing temperature. This trend was observed for all glassy alloys. The variation of the loss factor (tanwith frequency was measured at different temperatures. It was found that (tandecreases with increasing frequency and increases with increasing temperature.
The ac conductivity was found to increase with frequency. The value of the frequency exponent was found to have values ranging from 0.7 to 0.87 at room temperature and its value decrease with increasing temperature. The correlated barrier hopping model is considered to be applicable to the prepared glassy alloys.
The optical properties of as-deposited and annealed Se80 Te20-x Inx (where x = 0, 4, 6, 8 and 12 at. %) thin films have been studied. Various optical constants have been calculated. The optical absorption was found to obey the indirect transition. It was found that the optical energy gap (Eg) increases from 1.58 to 1.85 eV with increasing the In content. Similar trend was observed for the annealed thin films. It was found that the annealed thin films have lower values for (Eg) than as deposited thin films. The extinction coefficient was found to decrease with increasing temperature and also with increasing the In content. The refractive index has the same trend.