- Egypt
Abstract The objective of the present research is to investigate the consequences of the incorporation of a small amount of Cd on the electrical switching behavior at high electric field 104 V/cm in Se78-xTe20Sn2Cdx (x = 0, 2, 4, and 6)... more
Abstract The objective of the present research is to investigate the consequences of the incorporation of a small amount of Cd on the electrical switching behavior at high electric field 104 V/cm in Se78-xTe20Sn2Cdx (x = 0, 2, 4, and 6) thin films. The thermal evaporation method has been utilized for thin-film deposition on a highly polished pyrographite substrate. The current-voltage (I-V) characteristics for the thin films of the examined samples exhibit a resistive switching of memory-type. The effect of ambient temperature and Cadmium content on the switching characteristics and voltage has been studied. The exponential decay in the observed average value of the switching voltage (Vth) is found with the rise in temperature and Cd addition as well. An endeavor had been done to study the observed compositional dependence in terms of the thermal-induced glass transition temperature (Tg), thermal stability, chemical bond approach, and lone-pair electrons (LP). On metal addition (Cd), the threshold voltage, glass transition temperature, and lone-pair electrons decrease while the chemical order network increases by the increase of the Cd-Se homopolar bonds. The switching phenomenon in amorphous Se78-xTe20Sn2Cdx (0 ≤ x ≤ 6) thin films is elucidated according to an electro-thermal model based on the Joule-heating effect.
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Abstract The linear optical properties of amorphous GeSe2-xSnx (where 0 ≤ x ≤ 0.8) films were studied using spectrophotometric measurements of transmittance (T) and reflectance (R) at typical frequencies of light in the wavelength range... more
Abstract The linear optical properties of amorphous GeSe2-xSnx (where 0 ≤ x ≤ 0.8) films were studied using spectrophotometric measurements of transmittance (T) and reflectance (R) at typical frequencies of light in the wavelength range of 200–2500 nm. Structural properties affirm the amorphous nature of these films. Our investigations of the linear optical properties showed that the optical band gap decreases and the refractive index increases with an increase in Sn content in the Ge–Se system. It was found that the third-order nonlinear optical susceptibility is a function of Sn in the Ge–Se system. The values of the third-order nonlinear optical susceptibility increased with an increase in Sn content. The enhancement in the susceptibility of GeSe2-xSnx films (0 ≤ x ≤ 0.8) with an increase in Sn content could be explained in terms of the absorption edge.
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In2Se3 films of different thicknesses were prepared by thermal evaporation technique. X-ray diffraction measurements showed that the as-deposited In2Se3 films and those annealed at 373, 423, and 473K are in the amorphous state. The... more
In2Se3 films of different thicknesses were prepared by thermal evaporation technique. X-ray diffraction measurements showed that the as-deposited In2Se3 films and those annealed at 373, 423, and 473K are in the amorphous state. The composition of the investigated films is checked using energy dispersive X-ray spectroscopy (EDX) technique. The ac conductivity and dielectric properties of the amorphous In2Se3 films have been investigated in the frequency range 100Hz–100kHz. The ac conductivity σac(ω) is found to be proportional to ωs where s<1. The temperature dependence of both ac conductivity and the parameter s is reasonably well interpreted by the correlated barrier hopping (CBH) model. Values of dielectric constant ε1 and dielectric loss ε2 were found to decrease with frequency and increase with temperature. The maximum barrier height WM calculated from dielectric measurements according to Guintini equation agrees with that proposed by the theory of hopping of charge carriers over potential barrier as suggested by Elliot in case of chalcogenide glasses. The effect of annealing at different temperatures on the ac conductivity and dielectric properties is also investigated. Values of σac (ω), ε1, and ε2 were found to increase with higher annealing temperature due to the increase of the degree of ordering of the investigated films.
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Se70Te30 and Se70Te20Cd10 films of different thicknesses were prepared by thermal evaporation technique. X-ray diffraction patterns analysis showed that the films were in the amorphous state. The ac conductivity and dielectric properties... more
Se70Te30 and Se70Te20Cd10 films of different thicknesses were prepared by thermal evaporation technique. X-ray diffraction patterns analysis showed that the films were in the amorphous state. The ac conductivity and dielectric properties of the obtained films in the frequency range (102-105Hz) has been investigated. The ac conductivity is found to be proportional to ωs where s<1. The temperature dependence of both the ac conductivity and the parameter s is reasonably interpreted by the correlated barrier hopping CBH model. The maximum barrier height WM ,for each composition calculated from dielectric measurements according to Guintini equation, agrees with that proposed by the theory of hopping of charge carriers over potential barrier as suggested by Elliott in case of chalcogenide glasses.
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Se85Te10Bi5 films of different thicknesses ranging from 126 to 512 nm have been prepared. Energy-dispersive X-ray (EDX) spectroscopy technique showed that films are nearly stoichiometric. X-ray diffraction (XRD) measurements have showed... more
Se85Te10Bi5 films of different thicknesses ranging from 126 to 512 nm have been prepared. Energy-dispersive X-ray (EDX) spectroscopy technique showed that films are nearly stoichiometric. X-ray diffraction (XRD) measurements have showed that the Se85Te10Bi5 films were amorphous. Electrical conduction activation energy (DeltaEsigma) for the obtained films is found to be 0.662 eV independent of thickness in the investigated range. Investigation of the current voltage (I V) characteristics in amorphous Se85Te10Bi5 films reveals that it is typical for a memory switch. The switching voltage Vth increases with the increase of the thickness and decreases exponentially with temperature in the range from 298 to 383 K. The switching voltage activation energy (ε) calculated from the temperature dependence of Vth is found to be 0.325 eV. The switching phenomenon in amorphous Se85Te10Bi5 films is explained according to an electrothermal model for the switching process. The optical constants, the refractive index (n) and the absorption index (k) have been determined from transmittance (T) and reflectance (R) of Se85Te10Bi5 films. Allowed non-direct transitions with an optical energy gap (Egopt) of 1.33 eV have been obtained. DeltaEsigma is almost half the obtained value of Egopt, which suggested band to band conduction as indicated by Davis and Mott.
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Measurements of the dc and ac conductivity were made for polycrystalline CdSexTe1−x (0⩽x⩽0.4) at various frequencies (0.1–100kHz) and at various temperatures (293–413K). The temperature dependence of the dc conductivity was measured in... more
Measurements of the dc and ac conductivity were made for polycrystalline CdSexTe1−x (0⩽x⩽0.4) at various frequencies (0.1–100kHz) and at various temperatures (293–413K). The temperature dependence of the dc conductivity was measured in the temperature range (293–413K). It was found that the obtained dc activation energy for the investigated compositions decrease with the increase of Se content. The ac conductivity is found to be frequency and temperature dependent and obeys the Aωs law, where s decreases with the increase of temperature. The ac conductivity of these compositions are explained on the basis of the correlated barrier hopping model.
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Research Interests: Engineering, Materials Science, Materials, High Frequency, Thin Films, and 15 moreThin Film, DIELECTRIC, Activation Energy, Band Gap, Refractive Index, Optical Properties, CHEMICAL SCIENCES, Dielectric Constant, Room Temperature, Joule heating, Transmittance, Indexation, Film Thickness, Electric Conductivity, and Amorphous thin films
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ABSTRACT Se90Te10−xAgx (0≤x≤6) compositions were prepared by quenching technique. Thin films with different thicknesses of the obtained compositions were deposited on dry clean glass substrates by thermal evaporation technique. Energy... more
ABSTRACT Se90Te10−xAgx (0≤x≤6) compositions were prepared by quenching technique. Thin films with different thicknesses of the obtained compositions were deposited on dry clean glass substrates by thermal evaporation technique. Energy dispersive X-ray spectroscopy (EDX) indicates that samples are nearly stoichiometric. X-ray diffraction patterns indicate that they are in the amorphous state. The optical constants, the refractive index n and the absorption index k, have been calculated from transmittance T and reflectance R through the spectral range of 400–2500nm for the studied films with different thicknesses (165–711nm). From the analysis of refractive index n data, high frequency dielectric constant ɛ∞ was determined. Both ɛ∞ and n are found to decrease with the increase of Ag content. The optical band gap Egopt is calculated for all compositions from the absorption coefficient analysis. The effect of the Ag addition on the obtained optical parameters has been discussed. The analysis of absorption index k data, revealed the existence of allowed indirect transitions for all compositions. It is indicated also that Egopt increase with increasing Ag content.
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Abstract Ag33Sb31Se36 thin films were prepared by thermal evaporation technique on glass substrates. X-ray diffraction analysis for the as-deposited films showed that they have amorphous structure. On annealing at 200°C films have a... more
Abstract Ag33Sb31Se36 thin films were prepared by thermal evaporation technique on glass substrates. X-ray diffraction analysis for the as-deposited films showed that they have amorphous structure. On annealing at 200°C films have a polycrystalline structure. The optical constants n and k of the as-deposited and annealed films have been calculated from optical transmittance and reflectance data in the wavelength range 400–1500 nm using Murmann’s equations. Both n and k are practically independent on the film thickness in the range 182–478 nm. Analysis of the refractive index n yields a low frequency dielectric constant. The optical transitions are found to be allowed indirect for the as-deposited and annealed films, and the corresponding energy gaps increase with increasing annealing temperature.
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2 Te3 thin films of different thickness were prepared in a vacuum of 10-5 Torr onto glass and quartz substrates held at about 300 K during the deposition process. X-ray diffraction analysis showed that the prepared samples in bulk or... more
2 Te3 thin films of different thickness were prepared in a vacuum of 10-5 Torr onto glass and quartz substrates held at about 300 K during the deposition process. X-ray diffraction analysis showed that the prepared samples in bulk or as-deposited thin-film forms were in an amorphous state. On annealing at 573 K, films have a β-phase polycrystalline structure. Transmittance and reflectance measurements in the spectral
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Polyvinyl alcohol (PVA) films doped with erbium chloride (ErCl3) have been prepared by casting from their aqueous solutions. The structure of the doped samples as well as the interactions between the host PVA and Er+3was investigated... more
Polyvinyl alcohol (PVA) films doped with erbium chloride (ErCl3) have been prepared by casting from their aqueous solutions. The structure of the doped samples as well as the interactions between the host PVA and Er+3was investigated using FTIR spectroscopy. The optical measurement was recorded at room temperature in the range from 200 nm to 2000 nm. FTIR measurements revealed that Er+3forms complex configuration within the PVA structure. PVA doped with 9 wt% of ErCl3exhibits energy gap and refractive index of 5.1 eV and 1.72, respectively. The effect of the doping increment of ErCl3on the optical parameters has been discussed.
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Thin films of InSe were prepared by thermal evaporation technique under a vacuum of 10−4 Pa. The effect of γ- irradiation on the structure, and the optical parameters were investigated. The analysis of XRD of InSe proved that the... more
Thin films of InSe were prepared by thermal evaporation technique under a vacuum of 10−4 Pa. The effect of γ-
irradiation on the structure, and the optical parameters were investigated. The analysis of XRD of InSe proved that
the non-irradiated films have an amorphous background with a preferential orientation in the (002) direction.
The crystallite size was calculated and its value increases while increasing the γ-irradiation. The optical
parameters were obtained using spectrophotometric measurements of the transmittance and reflectance at
normal incidence of light at the wavelengths range 200–2500 nm. The type of optical transition was found to
be an indirect allowed transition, and it is found that the band gap increases while increasing γ-irradiation.
This post-irradiation increase in the band gap was interpreted in terms of bond rearrangements and changes
in the microstructure of these films. On the other hand, the dispersion parameters of InSe films were decreased
while increasing the irradiation dose
irradiation on the structure, and the optical parameters were investigated. The analysis of XRD of InSe proved that
the non-irradiated films have an amorphous background with a preferential orientation in the (002) direction.
The crystallite size was calculated and its value increases while increasing the γ-irradiation. The optical
parameters were obtained using spectrophotometric measurements of the transmittance and reflectance at
normal incidence of light at the wavelengths range 200–2500 nm. The type of optical transition was found to
be an indirect allowed transition, and it is found that the band gap increases while increasing γ-irradiation.
This post-irradiation increase in the band gap was interpreted in terms of bond rearrangements and changes
in the microstructure of these films. On the other hand, the dispersion parameters of InSe films were decreased
while increasing the irradiation dose
Transmission measurements in the spectral range of 40&900 nm in conjunction with the Kramers-Kronig relation were used in calculating the optical constants (the refractive index n and the absorption index k) of In,Se, thin films... more
Transmission measurements in the spectral range of 40&900 nm in
conjunction with the Kramers-Kronig relation were used in calculating the optical
constants (the refractive index n and the absorption index k) of In,Se, thin films
deposited at room temperature on a glass substrate. The refractive index n has
anomalous behaviour in the region of the fundamental absorption edge. The
allowed optical transitions were found to be indirect transitions with an optical gap
of 1.37 eV for the samples under test. On annealing, the gap increases with
temperature as well as with time periods of annealing in the case of In,Se, thin
films in the amorphous state. The increase in the value of €;PI with heat treatment
is interpreted in terms of the density of states model proposed by MotI and Davis.
Analysis of the refractive indices has yielded optical dielectric constants as a
function of temperature. X-ray analysis showed that the prepared sample in its bulk
form had CY phase, the prepared films at room temperature had amorphous
structure. When the temgerature is raised to 523 K, In,Se, films have ,%phase
polycrystalline structure.
conjunction with the Kramers-Kronig relation were used in calculating the optical
constants (the refractive index n and the absorption index k) of In,Se, thin films
deposited at room temperature on a glass substrate. The refractive index n has
anomalous behaviour in the region of the fundamental absorption edge. The
allowed optical transitions were found to be indirect transitions with an optical gap
of 1.37 eV for the samples under test. On annealing, the gap increases with
temperature as well as with time periods of annealing in the case of In,Se, thin
films in the amorphous state. The increase in the value of €;PI with heat treatment
is interpreted in terms of the density of states model proposed by MotI and Davis.
Analysis of the refractive indices has yielded optical dielectric constants as a
function of temperature. X-ray analysis showed that the prepared sample in its bulk
form had CY phase, the prepared films at room temperature had amorphous
structure. When the temgerature is raised to 523 K, In,Se, films have ,%phase
polycrystalline structure.