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In the present work, optical properties of Ge20S80−xGax thin films using transmission spectra have been described. Thin films of Ge20S80−xGax glassy alloy, obtained from melt quenching technique, were deposited on glass substrate by thermal evaporation technique under a high vacuum conditions (∼10−5 Torr). Glassy nature of thin films has been ascertained by X-ray diffraction pattern. Optical constants were estimated from transmission spectra recorded for the range 200 to 3000 nm using well established Swanepoel’s method. Refractive index has been found to be increase with an increase in Ga and shows a normal dispersion. Increase in refractive index is a consequence of increased polarization and density of the glassy alloy. Extinction coefficient has also been observed and noticed that it decreases with an increase in Ga content. Obtained optical properties are consistent with predicted physical properties of the Ge20S80−xGax glassy alloy. [ABSTRACT FROM AUTHOR]

In the present work, we have studied the effect of Ga doping on the physical properties of Ge20S80−xGax glassy alloy. The basic physical parameters which have important role in determining the structure and strength of the material viz. average coordination number, lone-pair electrons, mean bond energy, glass transition temperature, electro negativity, probabilities for bond distribution and cohesive energy have been computed theoretically for Ge-S-Ga glassy alloy. Here, the glass transition temperature and mean bond energy have been investigated using the Tichy-Ticha approach. The cohesive energy has been calculated by using chemical bond approach (CBA) method. It has been found that while average coordination number increases, all the other parameters decrease with the increase in Ga content in Ge-S-Ga system. [ABSTRACT FROM AUTHOR]

Thin films of Ge20S80−xGax glassy alloy, obtained from melt quenching technique, were deposited on the glass substrate by thermal evaporation technique under a high vacuum conditions (∼ 10-5 Torr). Absorption spectrum fitting method (ASF) is employed to obtain the optical band gap from absorption spectra. This method requires only the measurement of the absorption spectrum of the sample. The width of the band tail was also determined. Optical band gap computed from absorption spectra is found to decrease with an increase in Ga content. The evaluated optical band gap (Eg) is in well agreement with the theoretically predicted Eg and obtained from transmission spectra. [ABSTRACT FROM AUTHOR]

In this paper we have studied the effect of Ag addition on electrical properties of Se80.5Bi1.5Te18-yAgy (y = 1.0, 1.5 and 2.0 at. %) glassy system by using digital picometer (Keithley, model 6487) in the voltage range 0-300V. I-V study reveals that the glassy alloys under study exhibit ohmic behavior at low voltage and non-ohmic at high voltage. The field dependence studies for pellets reveal the ohmic nature of current for voltage less than 60V and non-ohmic nature of current for voltage greater than 60V. At higher voltage, greater than 60V, thermal effects come into plays which result in an increase in electrical conductivity. The d.c. conductivity is found to increase with an increase in Ag content. The conduction mechanism is discussed in terms of Poole-Frenkel conduction mechanism. The linearity of the plots between ln(I) and V1/2 shows that the conduction mechanism in the higher voltage range is of Poole-Frenkel type. [ABSTRACT FROM AUTHOR]

We report the calorimetric study of amorphous Se30Te70-x Snx alloys for x= 0, 1.5, 2.5, 4.5 in terms of kinetic parameters. The DSC curves recorded at four different heating rates are analyzed to determine the transition temperatures, activation energy, thermal stability, glass forming ability. The crystallization process has been investigated using Kissinger, Matusita, Augis and Bennett, and Gao and Wang models. Various kinetic parameters have been calculated for a better understanding of the growth mechanism. The glass transition temperatures Tg, onset crystallization Tc, peak crystallization Tp, and melting temperature Tm are found to increase with the increase in Sn content. The system under investigation is found to be thermally stable for at lower at% of Sn. The values of parameters HR, Hw, and S indicate that Glass forming ability (GFA) decays with an increase in Sn content. [ABSTRACT FROM AUTHOR]

An attempt is made to study the effect of Sn on the dielectric properties of Se-Te chalcogenide glasses. The effect of Sn doping on the a.c conductivity, dielectric constant and dielectric loss, of bulk Se30Te70-xSnx glassy alloy has been studied in the temperature range 311K-346K and frequency range 10 kHz to 500 kHz. It is found that the ac conductivity varies linearly with the frequency on increasing the temperature. The dielectric constant e' (real permittivity) and dielectric loss e? are also found to increases with the increase in temperature. The increase in conductivity is explained on the basis of Correlated Barrier hopping model. [ABSTRACT FROM AUTHOR]

Effect of Sb and Ag addition on the optical constants of SSe80.5Bi1.5Te18-yAy (A = Sb, Ag) and y = 2.0 at. %) thin films, prepared by thermal vacuum evaporation technique, is investigated using Swanepoel method. The optical constants i.e. refractive index (n), film thickness, absorption coefficient and optical energy gap are calculated from the transmission spectra. It has been found that refractive index increases with an increase in Sb or Ag content and the absorption coefficient is also found to increases with increase in optical energy. Whereas the optical band gap decreases with an increase in Sb content and increases with an increase in Ag content. Hence, the present results reveals that the addition of Sb and Ag produce remarkable change on the nonlinear optical properties of the thin film. [ABSTRACT FROM AUTHOR]

In the present work the effect of Sn doping on the physical properties of, tellurium rich, Se30Te70-xSnx system is studied theoretically. The average coordination number, constraints, lone pair electrons and heat of atomization for Se30Te70-xSnx system are calculated for x = 0,1.5,2.5,5.5 using the well defined relations. The present study shows that the values of lone pair electrons and average single bond energy goes on decreasing with increasing Sn content whereas the average coordination number, constraints and heat of atomization increases with increase in the Sn content. [ABSTRACT FROM AUTHOR]

The effect of Bi on the structural and optical properties of Se82-xBixTe18 glassy alloys is studied, theoretically. Cohesive energy is calculated by using chemical bond approach and is found to decrease with increasing Bi content. Optical band gap of thin films is calculated by Shimakawa's relation. The optical band gap decreases with increase in Bi content. [ABSTRACT FROM AUTHOR]