M.A. Abdel-Rahim

Kinetics study of non-isothermal crystallization in Se0.7Ge0.2Sb0.1 chalcogenide glass☆

Abstract Differential scanning calorimetry data at different heating rates on Se 0.7 Te 0.3 chalcogenide glass are reported and discussed. From the heating rate dependence of values of T g , T c and T p , the glass transition activation energy, E t , and the crystallization activation energy, E c , were derived. The crystallization data are interpreted in terms of recent analyses developed for non-isothermic crystallization and also for the evaluation of E c and the characterization of a crystallization mechanism. The results indicate that bulk crystallization with two-dimensional growth occurs for this glass. The calculated E t and E c are 143 ± 3 and 174 ± 8 kJ/mol, respectively.

Optical absorption studies on AgInSe2 and AgInTe2 thin films

Abstract The analysis of optical spectra of AgInSe 2 and AgInTe 2 thin films has been discussed. These ternary chalcopyrite compounds show an allowed direct transition near the fundamental absorption edge (E g1 ) in addition to a transition originating from crystal-field split levels (E g2 ). The calculated band tail in the first region (E e1 ) and (E e2 ) in the second region revealed that the crystallinity of AgInTe 2 was higher than that of the AgInSe 2 composition. The extinction coefficient ( k ) and refractive index ( n ) were also calculated for both compositions.

The effect of annealing on the optical absorption and electrical conduction of amorphous As24.5Te71Cd4.5 thin films

Abstract The optical absorption of as-prepared and thermally annealed As 24.5 Te 71 Cd 4.5 thin films was measured. The optical energy gap E o increased from 0.58 to 0.85 eV with increasing thickness of the as-prepared films from 58 to 125 nm. Films annealed at temperatures higher than 423 K showed a decrease in E o . The electrical conductivity of the as-prepared and annealed films was measured in the temperature range 80–300 K. An amorphous-crystalline transformation was observed after annealing at temperatures higher than 423 K. The results obtained are discussed on the basis of amorphous-crystalline transformations.

A study of the crystallization kinetics of some Se–Te–Sb glasses

Abstract Results of differential thermal analyses (DTA) under non-isothermal conditions on three glasses of the Se85−xTe15Sbx (x=0, 3 and 9) are reported and discussed. The glass transition temperatures (Tg), the onset crystallization temperatures (Tc), and the peak temperature of crystallization (Tp) were found to be dependent on the compositions and the heating rates. From the dependence on heating rates of (Tg) and (Tp) the activation energy for glass transition (Eg) and the activation energy for crystallization (Ec) are calculated and their composition dependence discussed. The crystalline phases resulting from DTA have been identified using X-ray diffraction and scanning electron microscopy (SEM). The results indicate one dimensional growth for the compositions Se82Te15Sb3 and Se76Te15Sb9 and two dimensional growth for the composition Se85Te15. The kinetic parameters determined have made it possible to discuss the glass-forming ability.

Experimental studies of the Ge-Sb-Se system

Abstract A systematic study was made of the semiconducting chalchogenide glass system Ge 20 Sb x Se 80− x with 5 x N ( E ), at the Fermi energy, on the annealing temperature.

Calorimetric studies of the glassy alloys in the GeSeTe system

Abstract Calorimetric studies of chalcogenide alloy glasses Ge 50 − x Se 50 Te x ( x = 10, 20, 40 at%) have been performed by continuous heating rates. The crystallization mechanism has been studied by differential scanning calorimeter (DSC), scanning electron microscopy (SEM) and X-ray diffraction. From the heating rate dependence of the glass transition temperature T g and the crystallization peak temperature T p , the kinetic parameters of crystallization were calculated and their composition dependence were discussed. The kinetic parameters determined have made it possible to discuss the glass forming ability as well as the different types of nucleation and crystal growth exhibited by the studied chalcogenide glasses.

Crystallization kinetics of selenium-tellerium glasses

Bulk glasses of the compositions Se70Te30 and Se80Te20 were prepared by the melt quenching technique. Differential thermal analyses were performed at different heating rates. The values of the glass transition temperature,Tg, the crystallization temperature,Tc, and the peak temperature of crystallization,Tp, were found to depend on the composition and the heating rate. The activation energy for the glass transition,Ei, as well as the activation energy for crystallization,Ec, were evaluated from the heating rate dependence ofTg andTp. The crystallization mechanism was examined through analysis of the data under non-isothermal conditions. The results indicated that surface crystallization is dominant for both compositions.

Differential scanning calorimetric study of Bi10Se80In10 chalcogenide glass

Results of differential scanning calorimetry under isothermal and non-isothermal conditions on Bi10Se80In10 glass are reported and discussed. By using the Johnson-Mehl-Avrami equation the activation energies for crystal growth have been evaluated and the crystallization mechanism has been studied. The results indicate that the crystallization process is a two-dimensional growth. The average calculated value of activation energy is 330.2 kJ mol−1for Bi10Se80In10 chalcogenide.

Crystallization kinetics and thermal stability in Se85-xTe15Sbx chalcogenide glasses

ABSTRACT Crystallization process of Se85-xTe15Sbx (x = 2.7, 7.5, 10 and 15 at %) chalcogenide glasses has been studied by using differential scanning calorimetry (DSC) with different heating rates. These glasses are found to have a double glasses transition and overlapped crystalline phases for Se70Te15Sb15 glass while single glasses transition and single crystallization stage for other glasses. Glass transition temperature, Tg, onset crystallization temperature, Tc, and peak crystallization temperature, Tp, are found to be dependent on composition and heating rates. Values of various kinetic parameters such as activation energy of glass transition, Eg, activation energy of crystallization, Ec, Hurby number, Hr, thermal stability, Sp, rate constant, Kp, and Avrami exponent, n, are determined for the present systems. Results indicate that rate of crystallization is dependent on thermal stability and glass-forming ability. Crystallization mechanism occurs in two dimensions for studied compositions. Crystalline phases resulting from DSC and scanning electron microscopy have been identified by using X-ray diffraction.

Crystallization study of Bi5Ge20Se75 glass

Results of thermal analysis performed at different heating rates on the composition Bi5Ge20Se75 are reported and discussed. The values of crystallization temperature (Tc) and the peak temperature of the crystallization (Tp) were found to be dependent on the heating rates. The activation energy of crystallization Ec was evaluated by five different methods. The average value of Ec is equal to 119.64+ 6.97 kJ mol−1.The crystallization data are examined in terms of recent analysis developed for non-isothermal conditions. The results indicate a two-dimensional crystal growth for the investigated composition.