Qasrawı, Atef Fayez Hasan

Qasrawı, Atef Fayez Hasan

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Qasrawi, Atef Fayez
Atef Fayez Hasan, Qasrawı
Qasrawı,A.F.H.
Qasrawi,A.F.H.
Q., Atef Fayez Hasan
Q.,Atef Fayez Hasan
Atef Fayez Hasan, Qasrawi
Qasrawi, Atef Fayez Hasan
A.F.H.Qasrawı
A.F.H.Qasrawi
A., Qasrawi
A.,Qasrawı
Qasrawı, Atef Fayez Hasan
Qasrawi, A. F.
Qasrawi,A.F.
Qasrawi, AF
Qasrawi, Atef F.
Qasrawi, Atef A.
Qasrawi, Atef Fayez
Qasrawi, Atef F.
Qasrawi, Atef A.
Qasrawi, Atef

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Doçent Doktor

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atef.qasrawi@atilim.edu.tr

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Scholarly Output

204

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201

Citation Count

1740

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Now showing 1 - 10 of 204

Citation Count: 10
Characterization of Au/As₂Se₃/MoO₃/Ag hybrid devices designed for dual optoelectronic applications
(Elsevier, 2020) Qasrawı, Atef Fayez Hasan; Qasrawi, A. F.; Kayed, Tarek Said; Department of Electrical & Electronics Engineering
In this work, hybrid devices composed of n-As2Se3/p-MoO3 encapsulated between two Schottky shoulders (Au/n-As2Se3, Ag/MoO3) are prepared and characterized. While the structural analyses proofed the preferred growth of monoclinic MoO3 onto amorphous layers of As2Se3, the spectroscopic ellipsometry analysis revealed the high frequency dielectric constants, the effective mass and the negative pseudodielectric constant values. Electrically, the hybrid device displayed both tunneling and standard diode characteristics. As passive mode devices, the capacitance-voltage characteristics displayed the accumulation-depletion -inversion modes in the device. Furthermore, the conductivity spectral analysis has shown that the current conduction is dominated by the quantum mechanical tunneling and correlated barriers hoping mechanisms. The amplitude of the reflection coefficient and the return loss spectral analyses indicated that the hybrid devices are band stop filters in addition to it is usability as nonlinear optical interfaces, CMOS device and tunneling diodes.
Citation Count: 5
Mechanical and electrical properties of Bi_1.5-xLa_xZn_0.92Nb_1.5O_6.92 pyrochlore ceramics
(Springer, 2016) Qasrawı, Atef Fayez Hasan; Kmail, Renal R. N.; Mergen, A.; Genc, Seval; Department of Electrical & Electronics Engineering
The physical properties of Bi1.5-xLaxZn0.92Nb1.5O6.92 solid solutions are investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy (EDS), and temperature dependent relative permittivity and electrical resistivity measurements. The La content which was varied from 0.10 to 0.60 is found to be solvable up to 0.21. Further increase in the amount of the La content caused the appearance of Bi0.4La0.6O1.5, LaNbO4, and ZnO minor phases in the pyrochlore matrix. While the lattice parameter and the theoretical, bulk and relative density are hardly affected by the increase in the La content, the strain, the dislocation density and the crystallite size are remarkably varied. The relative permittivity and temperature coefficient of relative permittivity are found to be sensitive to the La-Content. The electrical resistivity is observed to be temperature invariant below 390 K. It exhibits an insulator-semiconductor transition property at a critical temperature that increases with the increasing La content. Such observation is assigned to the increase in the dislocation density, which arises from the increment in the La content. The activation energies of the doped ceramics, which are determined from the electrical resistivity analysis are found to be similar to 1.12-1.00 eV.
Citation Count: 5
Properties of Se/InSe Thin-Film Interface
(Springer, 2016) Qasrawı, Atef Fayez Hasan; Kayed, T. S.; Kayed, Tarek Said; Department of Electrical & Electronics Engineering
Se, InSe, and Se/InSe thin films have been prepared by the physical vapor deposition technique at pressure of similar to 10(-5) torr. The structural, optical, and electrical properties of the films and Se/InSe interface were investigated by means of x-ray diffraction (XRD) analysis, ultraviolet-visible spectroscopy, and current-voltage (I-V) characteristics. XRD analysis indicated that the prepared InSe films were amorphous while the Se films were polycrystalline having hexagonal structure with unit cell parameters of a = 4.3544 and c = 4.9494 . Spectral reflectance and transmittance analysis showed that both Se and InSe films exhibited indirect allowed transitions with energy bandgaps of 1.92 eV and 1.34 eV, respectively. The Se/InSe interface exhibited two energy bandgaps of 0.98 eV and 1.73 eV above and below 2.2 eV, respectively. Dielectric constant values were also calculated from reflectance spectra for the three layers in the frequency range of 500 THz to 272 THz. The dielectric constant exhibited a promising feature suggesting use of the Se/InSe interface as an optical resonator. Moreover, the Au/Se/InSe/Ag heterojunction showed some rectifying properties that could be used in standard optoelectronic devices. The ideality factor and height of the energy barrier to charge carrier motion in this device were found to be 1.72 and 0.66 eV, respectively.
Citation Count: 3
In Situ Observation of Heat-Assisted Hexagonal-Orthorhombic Phase Transitions in Se/Ag/Se Sandwiched Structures and Their Effects on Optical Properties
(Springer, 2019) Qasrawı, Atef Fayez Hasan; Aloushi, Hadil D.; Department of Electrical & Electronics Engineering
In this work, two selenium layers of 500-nm thickness, nano-sandwiched with Ag nanosheets of 100-nm thickness (Se/Ag/Se), are subjected to in situ monitoring of the structural and optical transitions during heating over a temperature range of 303-473 K by x-ray diffraction and ultraviolet-visible light spectrophotometry, respectively. The Se/Ag/Se thin films are observed to exhibit a transformation from an amorphous to a polycrystalline phase at 343 K. Increasing the temperature above 363 K enhances the crystallinity of the hexagonal phase, reduces the microstrain, increases the crystallite size and reduces the defect density. Accordingly, the optical absorption spectra are redshifted upon heating. The redshift is accompanied by a transition in the energy band gap from 2.03 eV to 1.85 eV as the material structural phase is transformed from amorphous to polycrystalline. Increasing the temperature causes the energy band gap to shrink. Another permanent phase transformation from hexagonal to orthorhombic is detected when the Se/Ag/Se system is allowed to cool. Scanning electron microscopy images show that the phase transformation converts the grains of Se/Ag/Se films from wire-shaped to nanotubes. The second phase transformation causes a blueshift in the absorption coefficient spectra and increases the energy band gap. The structural and optical parameter enhancements achieved via heating render the Se thin films more suitable for optoelectronic applications.
Citation Count: 20
Investigation of carrier scattering mechanisms in TIInS₂ single crystals by Hall effect measurements
(Wiley-v C H verlag Gmbh, 2004) Qasrawı, Atef Fayez Hasan; Gasanly, NM; Department of Electrical & Electronics Engineering
TlInS2 single crystals are studied through the conductivity and Hall effect measurements in the temperature regions of 100-400 and 170-400 K, respectively. An anomalous behavior of Hall voltage, which changes sign below 315 K, is interpreted through the existence of deep donor impurity levels that behave as acceptor levels when are empty. The hole and electron mobility are limited by the hole- and electron-phonon short range interactions scattering above and below 315 K, respectively. An energy level of 35 meV and a set of donor energy levels located at 360, 280, 220 and 170/152 meV are determined from the temperature dependencies of the carrier concentration and conductivity. A hole, electron, hole-electron pair effective masses of 0.24 in,, 0.14 m(o) and 0.09 m(o) and hole- and electron-phonon coupling constants of 0.50 and 0.64, respectively, are obtained from the Hall effect measurements. The theoretical fit of the Hall coefficient reveals a hole to electron mobility ratio of 0.8. (C) 2004 WILEY-VCH Verlag Gmbh & Co. KGaA, Weinheim.
Citation Count: 11
In situ monitoring of heat assisted oxidation and its effects on the structural, dielectric and optical conductivity parameters of Pb thin films as promising terahertz transmitters
(Iop Publishing Ltd, 2019) Qasrawı, Atef Fayez Hasan; Abu Ghannam, Arwa N.; Department of Electrical & Electronics Engineering
In this work, thermal vacuum deposited lead thin films are subjected to an in situ monitoring of the oxidation process during heating in the temperature range of 300-480 K by the x-ray diffraction technique. The heating effects on the crystallinity, phase formation and structural parameters are additionally investigated with the help of computer simulation to explore the possible formed oxides. In addition, the heating effects of the optical transmission, reflection and absorption, optical conduction and terahertz signal transmission spectra are also investigated. It is found that, the cubic crystalline Pb films comprises tetragonal Pb3O4 in it's as grown form. When heated, while the Pb3O4 content increases from 18.5% to 21.3%, tetragonal PbO phase with weight of 30.9% is formed. Even though more than half of the film content relates to the oxides after the samples were left to cool, the microstrain and defect density in the films decreased and the grain size increased. Optically, the oxidation process enhanced, the light transitivity, reflectivity and decreased the absorption coefficient. Two energy band gaps one is assigned to Pb3O4 with value of 2.12 eV before heating and the other is assigned to PbO with value of 2.60 eV after cooling are detected. Dielectrically, the oxidation increased the real part and the quality factor in the infrared region of light. On the other hand, the optical conductivity analyses which are treated via Drude-Lorentz approach has shown that Pb films exhibit plasmon frequency and mobility values of 3.2 GHz and 0.62 cm(2) V-1 s(-1), respectively. The oxidation slightly lowered the optical conductivity parameters. Application directed analysis of the terahertz cutoff frequency has shown that the oxidized Pb films behaves as promising layers for use as terahertz wave transmitters suitable for visible light communications.
Citation Count: 3
Performance of the Yb/n-CdSe/C Tunneling Barriers
(Amer Scientific Publishers, 2018) Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering
In this article, the design and performance of the CdSe which are deposited onto thin films of Yb metal is reported and discussed. The thin films of CdSe which are deposited by the physical vapor deposition technique are observed to exhibit slightly deformed hexagonal polycrystalline nature with excess amount of Cd as confirmed by the X-ray, energy dispersive X-ray spectroscopy and scanning electron microscopy techniques. The n-type CdSe is also found to form a Schottky barrier of tunneling type when sandwiched between Yb and carbon. The quantum mechanical tunneling mechanism in this device which was tested and modeled in the frequency domain of 10-150 MHz is found to exhibit average intersite separations of similar to 5 nm. The tunneling device exhibited a widening in the depletion region associated with significantly large capacitance tunability in the studied frequency domain. On the other hand, as an optoelectronic device, the Yb/n-CdSe/C Schottky diode exhibited a responsivity of similar to 0.10 NW, photosensitivity of 6.5 x 10(4) and external quantum efficiency of 54% when biased with 1.0 V and exposed to laser light of wavelength of 406 nm.
Citation Count: 2
Crystal data and some physical properties of Tl₂InGaTe₄ crystals
(Wiley-v C H verlag Gmbh, 2007) Qasrawı, Atef Fayez Hasan; Gasanly, N. M.; Department of Electrical & Electronics Engineering
The room temperature crystal data, Debye temperature, dark and photoelectrical properties of the Bridgman method grown Tl2InGaTe4 crystals are reported for the first time. The X-ray diffraction technique has revealed that Tl(2)lnGaTe(4) is a single phase crystal of tetragonal body-centered structure belonging to the D-4H(18) - I4mcm space group. A Debye temperature of 124 K is calculated from the results of the X-ray data. The current-voltage measurements have shown the existence of the switching property of the crystals at a critical voltage of 80 V. The dark electrical resistivity and Hall effect measurements indicated the n-type conduction with an electrical resistivity, electron density and Hall mobility of 2.49x 10(3) Omega cm, 4.76x 10(12) cm(-3) and 527 cm V-2(-1) s(-1), respectively. The photosensitivity measurements on the crystal revealed that, the variation of photocurrent with illumination intensity is linear, indicating the domination of monomolecular recombination at room temperature. Moreover, the spectral distribution of the photocurrent allowed the determination of the energy band gap of the crystal studied as 0.88 cV.
Citation Count: 7
Photoelectronic and electrical properties of InS crystals
(Iop Publishing Ltd, 2002) Qasrawı, Atef Fayez Hasan; Gasanly, NM; Department of Electrical & Electronics Engineering
To identify the localized levels in InS single crystals, the dark electrical conductivity, current-voltage characteristics and photoconductivity measurements were carried out in the temperature range of 10-350 K. Temperature dependence of dark electrical conductivity and the space-charge limited current studies indicate the presence of a single discrete trapping level located at (10 +/- 2) meV below the conduction band with a density of about 4.8 x 10(11) cm(-3). The conductivity data above 110 K reveal an additional two independent donor levels with activation energies of (50 +/- 2) and (164 +/- 4) meV indicating the extrinsic nature of conductivity. The spectral distribution of photocurrent in the photon energy range of 0.8-3.1 eV reveals an indirect band gap of (1.91 +/- 0.04) eV. The photocurrent-illumination intensity dependence follows the law I-ph proportional to F-gamma, with gamma being 1.0 and 0.5 at low and high illumination intensities indicating the domination of monomolecular and bimolecular recombination, respectively. It is observed that the photocurrent increases in the temperature range of 10 K up to T-m = 110 K and decreases or remains constant for 110 K < T < 160 K and increases again above 160 K. The temperature dependence of the photocurrent reveals an additional shallow impurity level with activation energies of 3 meV.
Citation Count: 1
MgO/GaSe_0.5S_0.5 Heterojunction as Photodiodes and Microwave Resonators
(Ieee-inst Electrical Electronics Engineers inc, 2016) Qasrawı, Atef Fayez Hasan; Khanfar, Hazem K.; Gasanly, N. M.; Department of Electrical & Electronics Engineering
In this paper, a multifunctional operating optoelectronic device that suits visible light (VLC) and microwave communication systems is designed and characterized. The device which is composed of p-type MgO and n-type GaSe0.5S0.5 heterojunction is characterized by means of optical absorbance in the incident light energy (E) region of 3.5-1.1 eV, dark and illuminated current (I)-voltage (V) characteristics, and impedance spectra in the frequency range of 1M-1.8 GHz. Four types of lasers which generate light of wavelengths 406, 632, 850, and 1550 nm are used to excite the active region of the device. The device was also illuminated by non-monochromatic light. The incident light power was varied in the range of 1.12-10.17 mu W. It was observed that the heterojunction exhibits an optical energy bandgap (E-g) of 1.85 eV. For laser excitation with E > Eg, the photosensitivity (S) exceeds 67 while it is less than unity for excitations with E < Eg. These behaviors are assigned to the intrinsic and extrinsic nature of absorption, respectively. In addition, S increases as a result of energy barrier height lowering with increasing light power. On the other hand, when the device was excited with ac signal, the capacitance and impedance of the device displayed a resonance-antiresonance property associated with negative differential resistance and very high signal quality factor (10(3)) above 1.37 GHz. The bandwidth of the two resonance-antiresonance peaks is 319 and 12.6 MHz at 1.475 and 1.649 GHz, respectively. These results are attractive for using the heterojunction in VLC and microwave communication technologies.

Qasrawı, Atef Fayez Hasan

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Scholarly Output

204

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201

Citation Count

1740

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