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Films of Se80Te20−xSnx (where x = 6 at.%, 12 at.%, and 15 at.%) were prepared by thermal evaporation in a certain thickness of ~ 450 nm. Both the structural and electrical properties of as-prepared and annealed Se80Te20−xSnx films were studied. The annealing process was performed at 373 K, 393 K, and 413 K to cover the amorphous-crystalline region. Structural analyses show an improvement of film crystallinity with increasing both Sn content and annealing temperature. On the other hand, the electrical conductivity also shows significant enhancement with increasing Sn content and annealing temperature. The electrical results reveal that, at low temperature, conduction takes place through variable range hopping in localized states close to the Fermi level. Consequently, it has been shown in high temperature was explained by thermal charge carrier activation tunneling in the band tails of localized states. More structural and electrical parameters were evaluated for the Se80Te20−xSnx films to increase the understanding of the electronic properties of the Se-Te-Sn system.

Nanocrystalline of ZnAl2O4 spinel was synthesized by employing the microwave combustion method. Different new spinel compositions of formula Zn1-xFexAl2O4, (0.0 ≤ x ≤ 1.0) were prepared by substitution of Zn ions with Fe ions. The as-synthesized resultant material ZnAl2O4 with spinel structure as well as Zn1-xFexAl2O4 compositions were characterized by Energy Dispersive X-ray and X-ray diffraction. Morphology and particle size evaluation of the nanoparticles were characterized by transmission electron microscopy images. The optical absorption spectra and the magnetization were measured at room temperature for each Fe ratio. The substitution effect of Fe ions on the optical and magnetic properties of the original spinel was studied. The optical absorbance showed that the optical band gap decreased with increasing Fe ratio.

Chalcogenide glasses of (Se90Te10)100-x Inx (x = 0, 3, 6, 9, 11) alloys are prepared by melt quench technique. Differential scanning calorimetry (DSC) technique with different heating rate is used to study the dependence of the glass transition temperature (Tg) and fragility dynamics m on the In content in the Se-Te matrix. It is observed an increase of Tg with increasing In content. The glass transition temperature is differently defined according to the different degree of conversion of the glass. The activation energy of the glass transition (Eg) is evaluated using Kissinger, Moynihan kinetic and the partial area (isoconversional) methods. Analysis of experimental data shows that Eg changes with the degree of conversion from the glassy to the supercooled phase. The variation of the fragility with indium content is attributed to the formation of network structure. The employed theoretical models to describe the kinetics of the glass transition are valid.

Chalcogenide Se90Sb10 thin films are deposited by thermal evaporation from the bulk alloy. X-ray diffraction examination for the annealed films shows the amorphous-crystalline transformation. This is beneficial for optical disk data storage technology. The crystallinity is improved by increasing the annealing temperature. The films annealed at relatively low temperatures exhibit highly transparence reaching to about 90% at incident light of wavelength of 900 nm. The as-prepared and annealed Se90Sb10 films reveal an indirect allowed optical transition. The annealed film at 473 K has an optical band gap of 1.676 eV which is suitable value for solar cell as photovoltaic application. Both the indirect optical energy band gap (Eg) and the oscillator energy (Eo) decrease whereas the oscillator strength (Ed) increases with increasing the annealing temperature. The annealing increases the conductivity and decreases the activation energy for conduction resulting in enhancement of film properties for adapting to solar cells.

Recent chalcogenide-alkali metal Se80Te8(NaCl)12 semiconducting thin films of 750 nm thickness are deposited onto glass substrates by thermal evaporation method. The effect of the thermal annealing on structure and optical properties are investigated. The amorphous-to-crystalline phase transformation in the powdered sample is achieved by differential scanning calorimetry (DSC) heat treatment. The X-ray diffraction studies show that the as-prepared film is amorphous while the annealed films exhibit crystalline phases. The crystallite grain size decreases as the annealing temperature increases. The transmission spectra are measured in the wavelength range of the incident photons from 250 to 2500 nm. The films show highly transparence reaching about 90% in the visible and infrared regions. The refractive index of the films is calculated using the Swanepoel method based on the generation of the envelopes of the interference maxima and minima of the optical transmission spectrum. It progressively decreases with the incident wavelength representing the behavior of the normal dispersion of the film material. The effect of the annealing temperature on the refractive index is studied. The absorption mechanism of the films referred to indirect allowed transition. Optical band gap ranging from 1.60 to 1.45 eV is favorable for photovoltaics applications. With increasing the annealing temperature, both the optical band gap and the single-oscillator energy decrease while the energy of localized state increase.

Effect of annealing temperature on the structural and optical properties of As30Te60Ga10 thin film was studied using various techniques such as differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The DSC analysis revealed that the As30Te60Ga10 glass has a single glass transition and crystallization peak while XRD results confirmed that the as-prepared and annealed films have crystalline nature. The coexistence of the crystalline phases in the investigated films could be attributed to the formation of orthorhombic As, hexagonal Ga7Te10, and monoclinic As2Te3 phases. It was found that the average crystallite size and optical parameters of the studied films depend on the annealing temperature. For example, the optical band gap decreased from 1.54 eV to 1.11 eV as the annealing temperature increased from 300 K to 433 K.

This work reports the air-annealing effect on the structure, optical and electrical properties of tin sulfides (SnS) thin films and the capability of using these films for gas sensing application. The X-ray diffraction investigation shows that the predominant phase SnS (040) plane for the as-deposited film changes into Sn2S3 (201) plane after annealing. Furthermore, the annealed films at high temperatures (533 and 553 K) are partially oxidized leading to the formation of mixed tin sulfide oxides-Sn2S3 (MTO-Sn2S3) heterostructure thin film. The optical constants and thickness of films are calculated using Swanpole's method. Both optical band gap and electrical activation energy increased after annealing in the range (493–553 K) for 0.5 h in ambient air. Optical and electrical results indicate the existence of mixed phase characteristics of studied films. The gas sensing properties of MTO-Sn2S3 composite are investigated for methane gas detection. The fabricated sensor exhibits a weak sensitivity at low operating temperatures (50 and 100 °C). The sensitivity improves at high temperatures reaching its maximum at 250 °C. At 250 °C the response and recovery times are 250 and 82 s, respectively.

Thin films of In-doped Ge-S in the form of Ge35In8S57 with different film thickness were deposited using an evaporation method. The X-ray diffraction studies demonstrate that the as-prepared films are amorphous in nature for these films. Some optical constants were calculated at a thickness of 150, 300, 450 and 900 nm and annealing temperature of 373, 413, 437 and 513 K. Our optical observations show that the mechanism of the optical transition obeys the indirect transition. It was found that the energy gap, Eg, decreases from 2.44 to 2.20 eV with expanding the thickness of the film from 150 to 900 nm. On the other hand, it was found that Eg increases with annealing temperature from 373 to 513 K. The increment in the band gap can be attributed to the gradual annealing out of the unsaturated bonds delivering a decreasing the density of localized states in the band structure. Using the single oscillator model, the dispersion of the refractive index is described. The dispersion constants of these films were calculated with different both thickness and annealing temperatures. Additionally, both of nonlinear susceptibility, χ(3) and nonlinear refractive index, n2 were calculated.

Ge25Se75 chalcogenide films have been prepared using thermal evaporation method. X-ray diffraction (XRD) analysis shows polycrystalline natureof the annealed Ge25Se75 chalcogenide films at 340 °C. The significant transmittance of Ge25Se75 films at 1000 nm suggested the using of this material as an effective color filters. The indirect transition is the adopted mechanism of the electron transition for the as-deposited and the annealed Ge25Se75 films. The optical band gap energy ( E g ) was found to be increased as the annealing temperature increases. In the regime of the normal dispersion, the single oscillating energy ( E 0 ) , the dispersion energy ( E d ) values and the dielectric constant ( e ∞ ) for the as-prepared and annealed films were calculated. In the transparent region, the lattice dielectric constant ( e L ) was found to be decreased as the annealing temperature increases. Moreover, the measurements of the nonlinear optical parameters of these films at different annealing temperatures verify the possible using of thischalcogenide glass as a promised candidate material for optical applications.

Glasses of (Se90Te10)95M5 (where M = Zn and Bi) were prepared using a melt–quench procedure. These incorporated elements were chosen as examples of transition metals and basic metal groups, respectively. Thin films of these glasses at a thickness of 100 nm were evaporated onto cleaned glass substrates. Structural investigations were studied using XRD, SEM, and DSC. The glass transition, Tg, and Onset crystallization behavior of glasses, Tc of (Se90Te10)95M5 (M = Zn and Bi) alloys were analyzed using DSC at a heating rate of 15 K min−1. XRD patterns confirmed the amorphous nature of the films. The absorption coefficient, α, and refractive index, n, were obtained for (Se90Te10)95M5 (M = Zn and Bi) films. The Eg values of Se90Te10 increase as dopant by Zn. Conversely, it decreases as dopant by Bi. Moreover, the optical constants of (Se90Te10)95M5 (M = Zn and Bi) films were estimated. The estimated results confirm the applicability of modifying samples to be used using in optoelectronics applications.

The pre-crystallization and crystallization characteristics for Se 90-x Te 10 Ag x (where x = 4, 6 and 8 at.%) glasses were studied in this work by means of DSC under the non-isothermal conditions. Double stage endothermic glass transition, double stage exothermic crystallization and a single stage endothermic melting peaks were observed in the DSC curves. The annealed samples were then examined using XRD technique and the dominant crystalline phase has been identified. The average crystal sizes for the dominant crystalline phase in the annealed samples were calculated using Debye–Scherrer's formula and the effects of increasing Ag content are detailed. The Hrubý parameter values were assigned to the glasses under study. Moreover, the activation energies of the glass transition were calculated using different approaches at the glass transition temperatures and at different conversions. Also, the fragility index was calculated as a function of conversion and the glasses are found to mutate from being more fragile to be more strong throughout the relaxation process. On the other hand, a simple Gaussian function was able to deconvolute the crystallization overlapping peaks and the crystallization kinetics were calculated.

Chalcogenide-alkali metal semiconducting thin films of four different thicknesses of Se80Te8(NaCl)12 are deposited from bulk by thermal evaporation technique. The crystallinity of the film improves with increasing of thickness as indicated by the recorded X-ray diffraction patterns. The transmission and reflection spectra are measured in the wavelength range of the incident photons from 250 to 2500nm. The thickness and optical constants of the films are calculated based on Swanepeol method using the interference patterns appeared in the transmission spectra. It is found that the films have absorption mechanism which is an indirect allowed transition. The effect of the film thickness on the refractive index and the high-frequency dielectric constant are studied. With increasing the film thickness, both the absorption coefficient and high-frequency dielectric constant increase while the single-oscillator energy, optical band gap and extinction coefficient decrease.

Chalcogenide glasses have attracted much attention largely due to their interesting physical and chemical properties. Though few published articles exist on the As-Te system, little is known about the optical properties of eutectic or near eutectic composition of As-Te system upon heat treatment. Therefore, this paper reports the effects of annealing temperature on the structural and optical parameters of As30Te70 thin films. The bulk and thin films of 150 nm thick As30Te70 chalcogenide glasses were prepared by melt-quenching and thermal evaporation techniques, respectively. The glass transition and crystallization reactions of the bulk samples were investigated using differential scanning calorimetry (DSC). The influence of annealing temperature on the transformation of the crystal structure was studied by X-ray diffraction (XRD), while the surface morphology of the annealed samples was examined using scanning electron microscope (SEM). The optical band gap, refractive index and extinction coefficient were also calculated. The DSC scans showed that the melting temperature remains constant at 636.56 K. In addition, other characteristic temperatures such as the glass transition temperature, the onset crystallization temperature, and the crystallization peak temperature increase with increasing the heating rate. The crystalline phases for the as-prepared and annealed films consist of orthorhombic As, hexagonal Te, and monoclinic As2Te3 phases. Furthermore, the average crystallite size, strain, and dislocation density depend on the annealing temperature. The optical absorption results revealed that the investigated films have a direct transition, and their optical energy gap decreases from 1.82 eV to 1.49 eV as the annealing temperature increases up to 433 K. However, the refractive index, extinction coefficient, dielectric constant and the ratio of free carrier concentration to its effective mass, increase with increasing the annealing temperature.

A new chalcogenide-alkali metal alloy of $$\hbox {Se}_{80}\hbox {Te}_{8}(\hbox {NaCl})_{12}$$ has been prepared by a melt-quench technique. The crystallized phases due to the thermal annealing are observed by X-ray diffraction of the powdered sample. The glass transition and kinetics of crystallization in the $$\hbox {Se}_{80}\hbox {Te}_{8}(\hbox {NaCl})_{12}$$ alloy are studied using the differential scanning calorimetric technique under non-isothermal conditions. The activation energy of the glass transition is evaluated by Kissinger and Mahadevan methods. The crystallization activation energy ( $$E_{\mathrm{c}}$$ ) is calculated by isoconversion Friedman methods. The decrease of $$E_{\mathrm{c}}$$ with increasing crystallization conversion is attributed to the complex mechanism of the crystallization process. Based on the shape of the characteristic kinetic function, the crystallization growth is found to be a three-dimensional growth from the bulk nuclei. The results show that the conditions of the Sestak–Berggren model are satisfied for describing the crystallization process of the studied $$\hbox {Se}_{80}\hbox {Te}_{8}(\hbox {NaCl})_{12}$$ alloy. The parameters M and N involved in this model are calculated and related to the crystallization process.

Initially, Sulfur (S) doping in Se90Te10 glassy alloy was utilized for clarifying the effects produced by minerals on its glass mesh and kinetic characteristics. The crystallization kinetics of bulk Se90Te10 and (Se90Te10)95S5 with different heating rates were analyzed by the differential scanning calorimetry. The processes of the alloy recrystallization after the thermal treatment were recognized by X-ray diffraction. The activation of energy, Eg, of glass transition crystallization, Ec, was utilized for determining various kinetic models. The analysis and experimental data revealed that Eg and EC differ for the additive elements. The effective Ec of crystallization was calculated based on the Kissinger formula. Thus, the Sestak–Berggren model was used for characterizing the DSC crystallization information when it agreed to the experimental results. Consequently, it was found that the Johnson–Mehl–Avrami model can be applied at high heating rates.

This work introduces a new method of calculations depending on the essential assumptions of the kinetic methods, with the least amount of approximations to find the apparent kinetic parameters calculated for the crystallization of the Se90Te10 powders with heterogeneous particle sizes and shapes under non-isothermal conditions. The apparent kinetic parameters calculated by the new method are compared with that calculated blindly by applying Malek’s method, ignoring its applicability condition of invariant activation energy. The new method is based on the assumption that the kinetic function $$f\left( \alpha \right)$$ parameters are independent of the heating rate $$\beta$$ and time $$t$$ , and the fitting temperature function is assumed to be in the approximated form $$K\left( T \right) = K\left( {t,\beta } \right) = ct^{\text{r}} \beta^{\text{s}}$$ . The exponents $$r$$ and $$s$$ are calculated isoconversionally, while the constant $$c$$ and the kinetic function $$f\left( \alpha \right)$$ parameters are calculated by a curve fitting method using a generalized form of the Sestak and Berggren function, considering the steadily and logarithmic acceleration and deceleration of the curve. According to the data in this work, the fitting temperature function can be roughly approximated to the form $$K\left( T \right) \approx c/t$$ which work in with the physical dimensions of the rate constant. Moreover, the Arrhenian and the non-Arrhenian parameters, which describe the fitting temperature function $$K\left( T \right)$$ , are calculated isoconversionally. The deduced parameters work harmonically together to perfectly fit the experimental and the true data.

The structure of Ge 20 Se 80− x Sn x glassy alloys and crystallization phases are identified using the X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). The glass transition kinetics and the crystallization mechanism of the system are studied using Differential Scanning Calorimeter (DSC) under non-isothermal condition. The results reveal that glass transition temperature ( Tg ) increases with increasing Sn content which is attributed to the increase in the coordination number. The increase of the glass transition activation energy ( Eg ) with increasing Sn content is attributed to the decrease in the internal energy of the system as Sn increases. The compositional dependence of both glass forming ability and thermal stability are studied. From the experimental data, the thermal stability parameter ( S ) is found to be maximum for Ge 20 Se 78 Sn 2 alloy, which indicates that this alloy is thermally more stable in the composition range under investigation. The effect of composition on the crystallization mechanism is discussed using different kinetic models. The crystallization activation energy ( Ec ) decreases with increasing Sn. This is attributed to the addition of Sn increases the tendency of crystallization. The calculated values of Avrami exponent ( n ) indicates the crystallization process occurs in one-and two dimensions for Sn is less than or equals 12 at%, respectively.

Glasses of (Se90Te10)95M5 (M = In, Sb, and S) are set by melt-quench procedure. The incorporated elements were selected as examples from basic metal, semimetal, and nonmetal groups, respectively. Films of these glasses were evaporated onto glass substrates. The nature of the films was affirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The amorphous nature of the prepared films was confirmed by XRD measurements. Absorption coefficient, α, and refractive index, n, were estimated for all (Se90Te10)95M5 (M = In, Sb, and S) films. It is found that the optical band gap Eg decreases in the basic metal and semimetal groups, whereas it increases in the nonmetal group. The optical constants were estimated according to the single-oscillator model. The estimated results confirmed that the modified samples can be employed in the optoelectronic applications.

Cu3SbS3 (CAS) thin films are synthesized by the conventional thermal evaporation technique. The induced effects in optical and morphological properties of these films upon the annealing process in temperature range 473–623 K are studied. X-ray diffraction (XRD) analyses reveal the amorphous nature of the as-deposited film which crystallizes in monoclinic crystal structure after annealing. The absorption coefficient, refractive index and film thickness are calculated by Swanipoel's method. The observed optical band gap (Eg) shows a decrease in its value from 1.88 to 1.61 eV after annealing which is consistent with the detected red shift of absorption edge in the transmission spectra. The fabrication and the current-voltage (J-V) characteristics of Al/n-Si/p-CAS/Ag junction at different annealing temperatures are investigated. Dark measurements reveal good rectification behavior ≈ 102. Under illumination, the best performance is achieved for annealed cell at 523 K with short circuit current (Jsc) = 6.65 mAcm2, open circuit voltage (Voc) = 0.3 V, fill factor (FF) = 30% and conversion efficiency (η) = 1.49%.

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. Crystalli...

Amorphous chalcogenide Ge 20 Se 76 Sn 4 thin films of six different thicknesses (50–350 nm) are prepared by the thermal evaporation technique. Optical transmission and reflection spectra, in the wavelength range of the incident photons from 250 to 2500 nm, are used to study the effect of the film thickness on some optical properties. It is found that the effect of film thickness leads to increase in the absorption coefficient, refractive index, extinction coefficient and the width of the tails of localized states in the gap region. The decrease in optical band gap energy with increasing the film thickness is attributed to the formation of a band tail which narrows down the band gap. Dispersion analyses of refractive index reveal a decrease in the single-oscillator energy and an increase in the dispersion energy with increase in film thickness.

Chalcogenide thin films of Se82.5Te15Sb2.5 with different thickness (50–300 nm) are prepared by thermal evaporation technique. Crystalline phases of the deposited films are identified by x-ray diffraction (XRD). The influence of the film thickness and annealing temperature on the structure is studied by using XRD. The XRD studies show that the crystallinity improved by increasing film thickness and annealing temperature. Furthermore, the particle size and the crystallinity increase whereas dislocation density and strain decrease with increasing both the film thickness and annealing temperature. Transmittance and reflectance of the films are measured in wavelength range 300–2500 nm. It is found that, the optical energy gap, Eg, decreases and the localized state tails, Ee, increases by increasing film thickness and annealing temperature. Dispersion of the refractive index is described using Wemple–DiDomenico (WDD) single oscillator model. Dispersion parameters are calculated as a function of the film thickness and annealing temperature.

The present article deals with the differential thermal analyses (DTA) study of Se–Te glasses containing Sn. DTA runs are taken at six different heating rates (5, 10, 15, 18, 20, and 22 K min−1). The crystallization data are examined in terms of modified Kissinger, Mahadevan method, and Augis and Bennett approximation for the non-isothermal crystallization. Results of DTA under non-isothermal conditions on the glasses of the Se80Te20--xSnx (x = 3 and 9) are reported and discussed at different heating rates. 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 crystallization process of Se77.5Te15Sb7.5 glass is studied by differential scanning calorimetry (DSC) technique under non-isothermal conditions at various heating rates. The crystallization parameters are deduced using different models. The validity of the Johnson–Mehl–Avrami (JMA) model to describe the crystallization process for the studied composition is investigated. Comparing experimental and calculated DSC curves indicate that the crystallization process of Se77.5Te15Sb7.5 glass cannot satisfactorily be described by the JMA model. In general, simulation results indicate that the Sestak–Berggren model is more suitable to describe the crystallization kinetics. The crystalline phases are identified using the X-ray diffraction technique and scanning electron microscopy.

The crystallization kinetics of Se 70 Te 15 Sb 15 chalcogenide glass was studied by Differential Scanning Calorimetry (DSC) under non-isothermal conditions. This glass was found to have a double glass transition and double overlapped crystalline phases. The overlapped crystalline phases were successfully separated using the Gaussian fit model. The activation energy, E c , and Avrami index, n , were determined by analyzing the data using the Matausita et. al. method. A strong heating rate depending on the activation energy for the two crystalline peaks was observed. The results indicated that the transformation from amorphous to crystalline phases is a complex process involving different mechanisms of nucleation and growth. The variation of activation energy with crystalline fraction was determined by Kissenger–Akahira–Sunose (KAS) method. The obtained results of directly fitting the experimental DSC data to the calculated DSC curves indicated that the crystallization process of Se 70 Te 15 Sb 15 glass cannot be satisfactorily described by the Johnson–Mehl–Avrami (JMA) model. Simulation results indicated that the Sestak–Berggren (SB) model is more suitable to describe the crystallization process for the studied glass. The crystalline phases for the two events were identified by using x-ray diffraction (XRD) and scanning electron microscopy (SEM).

The glass transition and the crystallization kinetics of Zn10Se90 glass by differential thermal analysis (DTA) technique under non-isothermal conduction were studied. The effective activation energies of the glass transition and the crystallization have been evaluated on the basses of the Kissinger and Matusita et al. approximations. Kinetic parameters of the crystallization process are significantly influenced by the heating rate. We have compared the experimental DTA with the calculated data curves for Zn10Se90 system using the Johanson–Mehl–Avrami (JMA) and Sestak–Berggren SB(M,N) models. Simulation results indicated that the SB(M,N) model is more suitable for describing the crystallization kinetics for the studied composition. Furthermore, the crystalline phases of annealed Zn10Se90 were characterized by X-ray diffraction. The surface morphology of the annealed samples was examined using scanning electron microscopy.

The effect of annealing temperature (Ta) on the structural, optical, and electrical properties of thermally evaporated Cd20Sn10Se70 thin films has been investigated. Differential Thermal Analysis (DTA) was used to determine the glass transition temperature (Tg) of the prepared alloy. X-ray diffraction studies showed that the as-deposited film and the films that were annealed at Ta

Calorimetric measurements of chalcogenide Se95−xSb5Inx (x = 0, 6, 8 and 10 at%) alloys are carried out using differential thermal analysis (DTA). The glass forming ability and glass transition are analyzed based on the heating rate dependence. The ability to form crystals is found to be increased with increasing In content indicating the suitably for the anticipated storage. Both the glass transition temperature and the glass transition activation energy increase with increasing In content. The crystallization due to the addition of In to the Se–Sb system is investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM). The crystallization process is described by two models. These are Johnson–Mehl–Avrami (JMA) model and the empirical Sestak–Berggren (SB) model using an iso-conversional method of the transformation rate. The activation energy of crystallization is found to be increased with increasing In content. Based on the evaluated values of Avrami exponent (n), the crystallization growth is not dimensionally the same for the compositions.

The crystallization study under non-isothermal conditions of As30Te60Ga10 glass was investigated. The studied composition was synthesized by melt-quenching technique and characterized by different techniques such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The XRD analysis revealed that the as-prepared and annealed bulk glass of As30Te60Ga10 exhibit the amorphous, and polycrystalline nature, respectively. The DSC results showed that the heating rate affects the characteristic temperatures, for instance, the glass transition, onset, and peak crystallization temperatures. Furthermore, some thermal analysis methods such as the Kissinger and Matusita et al., approximations were employed to determine the crystallization parameters: for example Avrami exponent and the activation energies for glass transition and crystallization process. In addition, we have compared the experimental DSC data with the calculated ones based on the Johnson–Mehl–Avrami (JMA) and Sestak-Berggren SB(M,N) models. The results indicated that the SB(M,N) model is more suitable for describing the non-isothermal crystallization kinetics of the investigated composition.

Chalcogenide Se75Sb10In15 thin films of different thickness (50–300 nm) are deposited using thermal evaporation technique. The thermogram of the chalcogenide bulk Se75Sb10In15 is obtained using a differential scanning calorimetry (DSC). The crystallization temperature T c, peak crystallization temperature T p and melting temperature T m, are identified. The X-ray diffraction (XRD) examination indicates the crystallinity of the as-deposited film decreases with increasing of thickness. Optical transmission and reflection spectra are recorded in the wavelength range of the incident photons from 250 to 2500 nm. It is found that the film thickness affects the absorption coefficient, refractive index, extinction coefficient and the width of the tails of localized states in the gap region. The absorption mechanism of the as-deposited films is a direct allowed transition. The optical band gap energy (E g) decreases from 3.31 to 2.51 eV with increasing the film thickness from 50 to 300 nm. The behavior of E g is explained on the basis of the structure disorders in the thicker films. The effect of the film thickness on the single-oscillator and dispersion energies is studied by the dispersion analyses of the refractive index.

Amorphous Se85−x Te15Sb x (x = 2.5, 5 and 7.5 at.%) thin films were deposited on glass substrates by thermal evaporation. The absorption coefficient was determined from the transmittance, and reflectance spectra in the wavelength range 400–2500 nm. Various optical constants have been calculated for the studied compositions. The mechanism of the optical absorption follows the rule of non-direct transition. It was found that the optical energy gap, E g, decreases from 1.42 to 1.36 eV with increasing Sb content from 2.5 to 7.5 at.%. These results can be interpreted on the basis of the chemical bond approach proposed by Bicermo and Ovshinsky. On the other hand, the optical constants such as refractive index, n, and extinction coefficient, K ex, of the films were studied. The dispersion of the refractive index was discussed in terms of single-oscillator Wemple–DiDomenico model. The influence of Sb content on the structure for the annealed films was investigated using X-ray diffraction (XRD) and scanning electron microscopy. The average particle size of the crystalline size for Te0.04Se0.96 phase deduced from XRD pattern. This average decreases with increasing Sb content.

Coating nonmetallic-chalcogenide film material is developed to avoid oxidation and corrosion of the thin films. The chalcogenide part consists of a thin film of Se 60 Te 30 S 10 prepared by the thermal evaporation technique. On the other hand, the nonmetallic carbon thin film is applied onto the as-plated chalcogenide surface by deposition from an electrically heated carbon rod (arc discharge). The products obtained are characterized with X-ray diffraction and Scanning Electron Microscopy. It is observed an enhancement in crystallinity upon annealing for the as prepared uncoated and coated carbon films is observed. Optical studies reveal that carbon coating influences the optical energy gap, absorption coefficient and refractive index of the Se 60 Te 30 S 10 thin film.

Se 91 Te 9 and Se 81 Te 9 P 10 bulk glasses have been prepared by melt-quench technique. The amorphous nature of the as-prepared alloys is confirmed by using X-ray diffraction patterns. Thin films of Se 91 Te 9 and Se 81 Te 9 P 10 are prepared on chemically cleaned glass substrates by thermal evaporation under vacuum. Differential scanning calorimetery revealed a higher glass transition temperature for Se 91 Te 9 in comparison to Se 81 Te 9 P 10 bulk glasses. Transmission spectra of the as-prepared films are measured at normal incidence in the wavelength range of 300–2500 nm. Refractive index and the film thickness were determined from optical transmittance data using Swanepoel envelope method. It was found that the refractive index dispersion data obeys the single oscillator Wemple and DiDomenico model from which the dispersion parameters were determined. The single oscillator energy, the dispersion energy, the high frequency dielectric constant and the ratio of free charge carrier concentration to the effective mass are then estimated as a function of alloy composition. Analysis of the spectral behavior of the absorption coefficient revealed an allowed indirect optical band gap in this alloy system. With phosphorus incorporation, the optical band gap is found to decrease along with a subsequent increase in the refractive index. The ensemble of these results is interpreted in terms of the chemical bond approach, electronegativity difference of the atoms, cohesive energy and overall mean bond energy.

The structure of the as-prepared and thermal annealed Ag 10 As 30 S 60 chalcogenide glass is characterized using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) curves recorded at four different heating rates are analyzed to determine the glass and crystallization transition temperatures, thermal stability and enthalpy release. Two separated crystallization peaks are observed in the DSC curves. XRD results indicate the precipitation of AgAsS 4 crystal phase is responsible for the first peak. Numerous phases with S 8 dominant phase are accountable for the second peak. The crystallization kinetics such as the activation energy for the crystallization ( E c ), the frequency factor ( K o ) and the crystallization rate constant K are determined for each crystallization stage. The results show that the crystallization rate constant for the first crystallization stage is about six times larger than that of the second crystallization step.

Chalcogenide thin films of Ge 20 Se 70 Ag 10 of thicknesses 150, 300 and 450 nm are prepared by a thermal evaporation technique. The crystalline phases of the deposited film are identified by X-ray diffraction. The transmittance and reflectance of the films are measured in the wavelength range 200–2500 nm. The optical band gap decreases while the width of the localized states tail increases with increasing film thickness. Variation of refractive index and extinction coefficient with the film thickness is studied to analyze the optical efficiency of these films. Application of the single oscillator model to the films reveals that the oscillator energy decreases while the dispersion energy increases with increasing thickness. The variation of the optical constants suggests that the thickness change is a good choice to control the optical properties of Ge 20 Se 70 Ag 10 film.

In order to calculate the optical properties of evaporated Ge 30 Se 70 thin films and their relation to thickness, amorphous Ge 30 Se 70 thin films of different thicknesses were deposited by thermal evaporation at a base pressure of 7.5 × 10 −6 Torr at room temperature. The optical transmission and reflection spectra of all films were measured in the wavelength range of 0.2–2.5 μm. Efficient parameterization of the spectral dependence of the optical constants of amorphous Ge–Se thin films was obtained by applying a suitable dielectric function model. The O’Leary, Johnson and Lim (OJL) model, based on joint density of states functions, was used to analyze the optical spectra. The best fit was obtained by configuring the film as two layers, the top layer consisting of bulk Ge 30 Se 70 material embedded in air medium containing different volumes of voids. Therefore, the OJL model coupled with the Bruggeman effective-medium approximation model were used to determine the optical constants of the Ge 30 Se 70 thin films. The photon energy dependence of the dielectric function, ɛ = ɛ r − iɛ i of the investigated films is presented. The film thickness, absorption coefficient α , refractive index n , extinction coefficient k , static refractive index n ( 0 ) and optical band gap Eg were deduced. We found that increasing the film thickness increased the direct optical energy gap and decreased the refractive index.

The optical measurements of Se 30 Te 70 alloy thin film with different thicknesses (150, 450, 900 nm) are carried out in order to characterize their electronic structure and their optical constants using optical spectroscopy measurements. The optical absorption data point to an allowed indirect inter-band transition near the absorption edge. The estimated indirect E g values are 1.32, 1.19 and 0.854 eV for the studied film thicknesses. The observed decrease in the optical energy gap with thickness is attributed to the increasing the band tailing with increasing film thickness (Urbach tail effect). The optical constants such as the absorption coefficient, refractive index and extinction coefficient of the films are calculated from the measured transmission and reflection of these films. The results show the dependence of these optical constants on the film thickness. The X-ray diffraction reveals that the deposited films are poly-crystalline in nature with preferential (113) orientation.

The structural characterizations of Se 70 Te 30 chalcogenide glass for the as-prepared and thermal annealed samples are identified using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The isothermal thermal annealing process results in a transformation from the amorphous to the crystalline state. The average crystallite size increases from 8.67 to 11.24 nm when the temperature annealing increases from 95 to 118 °C. The thermal analyses of Se 70 Te 30 glass are investigated using a differential thermal analyzer (DTA) at five different heating rates under non-isothermal conditions. The activation energy of the glass forming ( E g ) as a parameter for the glass transition is estimated by employing different approaches proposed for thermal analyses. The study of crystallization kinetics includes the estimation of the activation energy of crystallization ( E c ), frequency factor ( K o ) and Avrami exponent ( n ).

The GexIn8Se92−x glasses (14 ≤ x ≤ 23.5) were extensively characterized by X-ray diffraction (XRD). The chemical composition is determined using energy dispersive spectrometers (EDS). The atomic structure of these glasses is investigated by using (XRD) technique. The first sharp diffraction peak (FSDP) in the structural factor indicates the existence of medium range order (MRO) in these glasses. The position of the FSDP and its full width at half maximum (FWHM), obtained after fitting the XRD of the glasses. The repetitive characteristic distance, R and structural correlation length, L, which characterizing the intermediate structure are deduced. The effect of composition and average coordination number , on the atomic volume, the density and compactness are studied. The connectivity of the system is discussed in terms of the total number of constraints which also influence the mean bond energy of the system. The intensity of the FSDP, the atomic volume and compactness of the structure, have anomalous change at = 2.67 indicating, a topological threshold occurs. The occurrence of this dependence leads to the Ge content has a marked effect on the MRO and physical properties parameters.

Amorphous Bi 5 Ge 40 Se 55 thin films have been deposited by thermal evaporation technique onto chemically cleaned glass substrates. The influence of thermal annealing on the optical properties of amorphous Bi 5 Ge 40 Se 55 films has been investigated. X-ray diffraction analysis (XRD) revealed that the as prepared film has an amorphous nature while the annealed films shows two crystalline phases GeSe 2 and Bi 2 Se 3 in monoclinic and hexagonal crystal structure with a preferential orientation along 〈1 2 5〉 direction. Optical reflectance and transmittance of the as prepared and annealed films were measured in the wavelength range 300–900 nm using a double beam spectrophotometer. The optical band gap E g decreased with increasing of the annealing temperature. This behavior of E g was discussed in terms of the width of localized stat i.e. Mott and Davis model for amorphous–crystalline structure transformation. Some of the important optical constants such as optical dispersion energies; E o and E d , dielectric constants; e ∞ and e L as well as the ratio between number of charge carriers and effective mass n / m * have been evaluated.

The effect of composition on the optical constants of Se100−xTex (x = 30, 50, 70) chalcogenide thin films of thickness 150 nm are studied. The film is deposited on glass substrate using thermal evaporation technique under vacuum. X-ray diffraction reveals that the poorly Te content Se70Te30 film has amorphous structure while the other films have crystalline phases. Both the transmittance and reflectance are strongly dependent on the film composition. The analyses of optical measurements show that the Se30Te70 film has two absorption mechanisms which are direct and indirect allowed transitions giving raise two optical energy gaps. Increasing of Se content changes the direct gap to an indirect one. The increase of Se contents (from x = 30 to 70) leads to increase in the indirect gap from 1.33 to 1.85 eV. The absorption coefficient, refractive index, extinction coefficient and dispersion energy of the films are found to be depended on the film composition.

Amorphous Cd20Se80−xMx (M: Zn or In or Sn and x=0 & 10) thin films were deposited on glass substrates by thermal evaporation. The spectral dependence of the absorption coefficient was determined from the transmittance and reflectance spectra, in the wavelength range 200–2500 nm. Both direct and indirect electronic transitions were responsible for the optical properties of Cd20Se80 thin films while only the direct allowed transition was active for the other films alloys. The variation in the optical band gap (Eg) with the addition of the third element was discussed in terms of the width of localized states (Ee) and chemical bond approach model (CBA). The optical constants (refractive index (n) and absorption index (k)) of the films were studied and the dispersion of the refractive index was discussed using the Wemple–DiDomenico single oscillator model. The real and imaginary parts of the dielectric constant in addition to the volume (VELF) and surface (SELF) energy loss functions of the films were also determined. Generally, the addition of Zn was found to have the opposite effect to that of In or Sn addition.

Bulk of ZnxSe100−x (x=10, 20 and 40 at%) was prepared by the usual quench melt technique. Thin films of these compositions were prepared by thermal evaporation. Differential thermal analyses (DTA) on powder samples under non-isothermal conditions show that the glass transition temperature Tg increased and crystallization temperature Tp decreased with increasing Zn content. The average particle size of the crystalline ZnSe phase deduced from X-ray diffraction (XRD) patterns show a decrease with increasing Zn content. These results were confirmed with the results obtained by scanning electron microscopy (SEM). The optical properties of ZnxSe100−x have been studied at a wavelength range (300–900 nm), and it was found that the optical band gap (Eg) increases with increasing Zn concentration in the ZnxSe100−x system. The results can be interpreted on the basis of the chemical bond approach proposed by Bicermo and Ovshinsky. The value of the extinction coefficient (k) decreases with increasing wavelength and Zn content. On the other hand, the optical energy gap (Eg) decreased with increasing the annealing temperature for Zn10Se90 thin films. These results can be interpreted by the Davis and Motte model.

Chalcogenide Se50Te20S30 thin film of different thickness was deposited using thermal evaporation technique. The thermogram of the chalcogenide bulk Se50Te20S30 was obtained using a differential scanning calorimetry (DSC) with heating rate of 7.5 K/min. The glass transition temperature T g, crystallization temperature T c and peak crystallization temperature T p were identified. The X-ray diffraction (XRD) examination indicates the amorphous nature of the as-deposited film and polycrystalline structure of the thermal annealed ones. The dark electrical resistivity (ρ) measurements were taken in temperature range (300–500 K) and thickness range (200–450 nm). Analysis of the electrical resistivity results revealed two types of conduction mechanisms: conduction due to extended states in the temperature range (T > T c) and variable range hopping in the temperature range (T

Thin films of Zn 40 Se 60 were prepared by the vacuum thermal evaporation technique. The influence of annealed temperature on the structural and optical properties was investigated using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical transmission. The XRD studies show that the as-deposited film is amorphous in nature, but the crystallinity improved with increasing the annealing temperature. Furthermore the particle size and crystallinity increased whereas the dislocation and strains decreased with increasing the annealing temperature. SEM studies showed that the annealing temperature induced changes in the morphology of the as-deposited sample. Various optical constant have been calculated for as-deposited and annealed films. The mechanism of the optical absorption follows the rule of direct transition. It was found that, the optical energy gap ( E g ) decreased with increasing the annealing temperature. These results can be interpreted by the Davis and Motte model. On the other hand the maximum value of the refractive index ( n ) is shifted toward the long wavelength by increasing the annealing temperature.

Bi5GexSe95−x (30, 35, 40 and 45 at.%) thin films of thickness 200 nm were prepared on glass substrates by the thermal evaporation technique. The influence of composition and annealing temperature, on the structural and electrical properties of Bi5GexSe95−x films was investigated systematically using X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX). The XRD patterns showed that the as-prepared films were amorphous in nature with few tiny crystalline peaks of relatively low intensity for 30 and 45 at.% and the Bi5Ge40Se55 annealed film was polycrystalline. The chemical composition of the Bi5Ge30Se65 film has been checked using energy dispersive X-ray spectroscopy (EDX). The electrical conductivity was measured in the temperature range 300–430 K for the studied compositions. The effect of composition on the activation energy (ΔE) and the density of localized states at the Fermi level N(EF) were studied, moreover the electrical conductivity was found to increase with increasing the annealing temperature and the activation energy was found to decrease with increasing the annealing temperature. The results were discussed on the basis of amorphous-crystalline transformations.

Structural and optical properties of selenium-rich CdSe (SR-CdSe) thin films prepared by thermal evaporation are studied as a function of annealing temperature. X-ray diffraction (XRD) patterns show that the as-prepared films were amorphous, whereas the annealed films are polycrystalline. Analyzing XRD patterns of the annealed films reveal the coexistence of both (hexagonal) Se and (hexagonal) CdSe crystalline phases. Surface roughness of SR-CdSe films is measured using atomic force microscope (AFM). Analyses of the absorption spectra in the wavelength range (200–2500 nm) of SR-CdSe thin films indicates the existence of direct and indirect optical transition mechanisms. The optical band gap ( E g ) of as-prepared film is 1.92 and 2.14 eV for the indirect allowed and direct allowed transitions respectively. After annealing, the absorption coefficient and optical band gap were found to decrease, while the values of refractive index ( n ) and the extinction coefficient ( k ex ) increase. The dispersion of the refractive index is described using the Wimple–Di Domenico (WDD) single oscillator model and the dispersion parameters are calculated as a function of annealing temperature. Besides, the high frequency dielectric constant ( ɛ ∞ ) and the ratios of the free carrier concentration to its effective mass ( N / m *) are studied as a function of annealing temperature. The results are discussed and correlated in terms of amorphous-crystalline transformations.

Different compositions of Bi 5 Ge x Se 95− x ( x = 30, 35, 40 and 45 at %) thin films were deposited onto cleaned glass substrates by thermal evaporation method. The structural characterization revealed that, the as-prepared films of x = 30, 35 and 40 at. % are in amorphous state but there are few tiny crystalline peaks of relatively low intensity for the film with x = 45 at. %. The chemical composition of the as-prepared Bi 5 Ge x Se 65− x films has been checked using energy dispersive X-ray spectroscopy (EDX). The optical properties for the as-deposited Bi 5 Ge x Se 65− x thin films have been studied. The additions of Ge content were found to affect the optical constants (refractive index, n and the extinction coefficient, k ). Tauc’s relation for the allowed indirect transition is successfully describing the mechanism of the optical absorption. It was found that, the optical energy gap ( E g ) decreases with the increase in Ge content. These obtained results were discussed in terms of the chemical bond approach proposed by Bicermo and Ovshinsky. The composition dependence of the refractive index was discussed in terms of the single oscillator model.