Qasrawı, Atef Fayez Hasan

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https://hdl.handle.net/20.500.14411/7716
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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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atef.qasrawi@atilim.edu.tr
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Department of Electrical & Electronics Engineering
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Former Staff
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Scholarly Output

226

Articles

222

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721/0

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0

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WoS Citation Count

1970

Scopus Citation Count

2000

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0

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WoS Citations per Publication

8.72

Scopus Citations per Publication

8.85

Open Access Source

17

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0

JournalCount
Crystal Research and Technology16
Journal of Electronic Materials15
physica status solidi (a)12
Materials Science in Semiconductor Processing11
Journal of Alloys and Compounds11
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Start date: 2010Subject: Optical properties

Scholarly Output Search Results

Now showing 1 - 10 of 11
  • Thumbnail Image
    Article
    Citation - WoS: 11
    Citation - Scopus: 14
    Structural, optical, electrical and dielectric properties of Bi1.5Zn0.92Nb1.5-xNixO6.92-3x/2 solid solution
    (Taylor & Francis Ltd, 2012) Qasrawi, A. F.; Nazzal, E. M.; Mergen, A.
    The effects of Ni content on the structural, optical, dielectric and electrical properties of Bi1.5Zn0.92Nb1.5O6.92 pyrochlore ceramics have been investigated. Nickel atoms were inserted into pure samples in accordance to the composition Bi1.5Zn0.92Nb1.5-xNixO6.92-3x/2, with x varying from 0.07 to 0.40. The structural analysis revealed that a single phase of the pyrochlore compound can be obtained for x values of 0.07 and 0.10 only. Further increase in Ni caused the appearance of multiple phases. The optical energy band gaps are determined as 3.30, 3.35 and 3.52 eV for Ni content of 0.00, 0.07 and 0.10 respectively. The temperature dependent electrical resistivity and the frequency dependent capacitance are observed to increase with increasing Ni content. The resonance frequency, which was determined from the capacitance-frequency dependence, was observed to shift from 12.14 to 10.47 kHz as the x values increase from 0.00 to 0.10 respectively.
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    Article
    Citation - WoS: 12
    Citation - Scopus: 12
    Energy Band Gap and Dispersive Optical Parameters in Bi1.5zn0.92< Pyrochlore Ceramics
    (Elsevier Science Sa, 2010) Qasrawi, A. F.; Mergen, A.
    The compositional and optical properties of Bi1.5Zn0.92Nb1.5O6.92 Pyrochlore ceramics have been investigated by means of scanning electron microscopy (SEM) and UV-vis spectroscopy, respectively. The SEM spectroscopy revealed that the pyrochlore exhibits a very dense microstructure with single-phase appearance. The absorption spectral analysis in the sharp absorption region revealed an indirect forbidden transitions band gap of 3.30 eV. The room temperature refractive index, which was calculated from the reflectance and transmittance data, allowed the identification of the dispersion and oscillator energies, static and lattice dielectric constants and static refractive index as 26.69 and 3.37 eV, 8.92 and 15.95 and 2.98, respectively. (C) 2010 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 9
    Citation - Scopus: 9
    Structural and Optoelectronic Properties of Cds/Y Thin Films
    (Elsevier Science Sa, 2019) Qasrawi, A. F.; Abed, Tamara Y.
    In the current study, the structural, optical, photoelectrical and electrical properties of CdS/Y/CdS thin films are investigated. The current design include the evaporation of a layer of 70 nm thick yttrium between two layers of CdS. Each CdS layer is of thickness of 500 nm. It is observed that the yttrium slab increased the microstrain, defect density, stacking faults and decreased the grain size and redshifts the indirect allowed transitions energy band gap of CdS. In addition an enhancement by similar to 5 times in the light absorbability is detected at 1.74 eV. The enhanced absorbance results in increasing the photocurrent by similar to 21 times and changed the recombination mechanism from a trap assisted recombination to supralinear recombination mechanisms. Moreover, the ac signal analysis in the frequency domain of 10-1800 MHz has shown that the yttrium forces the CdS to exhibit negative capacitance effect and make it behave as band stop filter with notch frequency of 1520 MHz. The quality of the CdS/Y/CdS films as microwave cavities are screened by the evaluation of the return loss which revealed good features of the nanostructured films as microwave receivers.
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    Article
    Citation - WoS: 7
    Citation - Scopus: 7
    In situ monitoring of the permanent crystallization, phase transformations and the associated optical and electrical enhancements upon heating of Se thin films
    (Elsevier Science Bv, 2019) Qasrawi, A. F.; Aloushi, Hadil D.
    In this work, the in situ structural transformations from amorphous to polycrystalline upon heating and the associated enhancements in the structural parameters of selenium thin films are studied by means of X-ray diffraction technique. The Se thin films which are grown onto ultrasonically cleaned glass substrate by the thermal evaporation technique under vacuum pressure of 10(-5) mbar exhibits structural transformation from amorphous to polycrystalline near 353 K. The films completed the formation of the structure which includes both of the hexagonal and monoclinic phases at 363 K. It is observed that the hexagonal phase dominates over the monoclinic as temperature is raised. Consistently, the thermally assisted crystallization process is accompanied with increase in the crystallite size, decrease in the microstrain, decrease in defect density and decrease in the percentage of stacking faults. The scanning electron microscopy measurements also confirmed the crystallinity of selenium after heating. The time dependent reputations of the crystallization test has shown that the achieved phase transitions and enhancements in structural parameters are permanent in selenium. Optically, the crystallization process is observed to be associated with redshift in the absorption spectra and in the value of the energy band gap. Electrically, the in situ monitoring of the electrical conductivity during the heating cycle has shown that the electrical conductivity stabilizes and exhibit a decrease in the acceptor levels from 566 to 321 meV after the crystallization was achieved.
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    Article
    Citation - WoS: 10
    Citation - Scopus: 11
    Temperature effects on the optoelectronic properties of AgIn5S8 thin films
    (Elsevier Science Sa, 2011) Qasrawi, A. F.
    Polycrystalline AgIn5S8 thin films are obtained by the thermal evaporation of AgIn5S8 crystals onto ultrasonically cleaned glass substrates under a pressure of similar to 1.3 x 10(-3) Pa. The temperature dependence of the optical band gap and photoconductivity of these films was studied in the temperature regions of 300-450 K and 40-300 K, respectively. The heat treatment effect at annealing temperatures of 350, 450 and 550 K on the temperature dependent photoconductivity is also investigated. The absorption coefficient, which was studied in the incidence photon energy range of 1.65-2.55 eV, increased with increasing temperature. Consistently, the absorption edge shifts to lower energy values as temperature increases. The fundamental absorption edge which corresponds to a direct allowed transition energy band gap of 1.78 eV exhibited a temperature coefficient of -3.56 x 10(-4) eV/K. The 0 K energy band gap is estimated as 1.89 eV. AgIn5S8 films are observed to be photoconductive. The highest and most stable temperature invariant photocurrent was obtained at an annealing temperature of 550 K. The photoconductivity kinetics was attributed to the structural modifications caused by annealing and due to the trapping-recombination centers' exchange. (C) 2010 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Mixed Conduction and Anisotropic Single Oscillator Parameters in Low Dimensional Tlinse2 Crystals
    (Elsevier Science Sa, 2013) Qasrawi, A. F.; Gasanly, N. M.
    Due to the importance of the TlInSe2 crystal as neutron and gamma-ray detectors, its electrical and dispersive optical parameters have been investigated. Particularly, the anisotropic current conduction mechanism in the temperature region of 100-350 K and the room temperature anisotropic dispersive optical properties were studied by means of electrical conductivity and optical reflectance, respectively. It has been shown that the mixed conduction is the most dominant transport mechanism in the TlInSe2 crystals. Particularly, when the electric field is applied perpendicular to the crystal's c-axis, the main dominant current transport mechanism is due to the mixed conduction and the variable range hopping above and below 160 K, respectively. When the electric field is applied parallel to the crystal's c-axis, the electrical conductivity is dominated by the thermionic emission, mixed conduction and variable range hopping at high, moderate and low temperatures, respectively. The optical reflectivity analysis in the wavelength range 210-1500 nm revealed a clear anisotropy effect on the dispersive optical parameters. Particularly, the static refractive index, static dielectric constant, dispersion energy and oscillator energy exhibited values of 2.50, 6.24, 20.72 eV and 3.96 eV, and values of 3.05, 9.33, 39.27 eV and 4.72 eV for light propagation parallel and perpendicular to the crystal's c-axis, respectively. Moreover, the frequency dependence of the dielectric constant, epsilon(omega), reflected strong dielectric anisotropy that exhibit maximum epsilon(omega) value of 38.80 and 11.40 at frequencies of 11.07 x 10(14) Hz for light propagation parallel and perpendicular to the crystal's c-axis, respectively. The anisotropy in the epsilon(omega) makes the TlInSe2 crystals attractive to be used as nonvolatile static memory devices. (C) 2013 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Effect of Insertion of Aluminum Nanosheets on the Structural, Optical and Dielectric Properties of Stacked Layers of Selenium
    (Natl inst R&d Materials Physics, 2019) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Abu Al Rob, O. H.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
    In this work, the time dependent metal induced crystallization process in stacked layers of selenium that are sandwiched with aluminum nanosheets of thicknesses of 50 nm are investigated by means of X-ray diffraction and optical spectrophotometry techniques. The Al nanosheets motivated the growth of orthorhombic phases of selenium and lowered the energy bang gap of the amorphous films from 2.26 to 1.82 eV when the orthorhombic phase is achieved. The time dependent monitoring of the structural and optical properties over eighteen months have shown that both of the orthorhombic and amorphous phases exhibit a second transformation to hexagonal and stabilize at that phase within ten days of the growth time. The presence of the aluminum nanosheets enhanced the light absorbability by 15 and 5 times in the orthorhombic and hexagonal phases, respectively. In addition, the dielectric spectra of the studied films display similar characteristics in the hexagonal phase with slight differences that results from Al nanosheets. The dielectric spectra for both of the amorphous and orthorhombic phases displayed resonance peaks in the visible and infrared ranges of light. The structural and optical analysis that are carried out through this study represent a guide for using the selenium films in optoelectronic technology.
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    Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Band Offsets and Optical Conduction in the Cdse/Gase Interface
    (Elsevier Science Bv, 2016) Kayed, T. S.; Qasrawi, A. F.; Elsayed, Khaled A.
    In this work, the design and characterization of CdSe/GaSe heterojunction is considered. The CdSe/GaSe thin film interface was prepared by the physical vapor deposition technique. Systematic structural and optical analysis were performed to explore the crystalline nature, the optical band gaps, the conduction and valence band offsets, the dielectric spectra, and the frequency dependent optical conductivity at terahertz frequencies. The X-ray diffraction analysis revealed a polycrystalline interface that is mostly dominated by the hexagonal CdSe oriented in the (002) direction. It was also found that the CdSe/GaSe interface exhibits conduction and valence band offsets of 1.35 and 1.23/1.14 eV, respectively. The dielectric spectra displayed two dielectric resonance peaks at 530 and 445 THz. Moreover, the computational fittings of the optical conductivity of the interface revealed a free carrier scattering time of 0.41 (fs) for a free carrier density of 7.0 x 10(18) (cm(-3)). The field effect mobility for the CdSe/GaSe interface was found to be 5.22 (cm(2)/Vs). The remarkable features of this device having large band offsets and qualitative optical conduction dominated by a scattering time in the order of femtoseconds in addition to the dielectric property nominate the device to be used in optoelectronic technology. (C) 2016 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 11
    Citation - Scopus: 11
    Post Annealing Effects on the Structural, Compositional, Optical and Dielectric Properties of Cd Doped Gase Thin Films
    (Elsevier Science Sa, 2015) Al Garni, S. E.; Qasrawi, A. F.
    In this work, the heat treatment effects at temperatures (T-a) of 200, 300 and 400 degrees C on the compositional, structural, optical and dielectric properties of Cd doped GaSe are explored by means of energy dispersive X-ray spectroscopy, X-ray diffraction and UV-VIS spectrophotometry. The annealing process of the Cd doped GaSe thin films revealed a highly oriented orthorhombic structure type that exhibit a systematic increase in the grain size. While the strain, degree of orientation and dislocation density of the annealed films are weakly affected by the annealing process. The optical energy band gap of the doped films decreased from 1.23 to 0.90 eV and the exponential energy band tails rose from 0.16 to 0.23 eV when the annealing temperature is raised from 300 to 400 degrees C. In addition, the analysis of the dielectric spectral curves which were studied in the frequency range of 270-1500 THz, allowed to investigate the oscillator and dispersion energies and the static (epsilon(s)) and lattice (epsilon(l)) dielectric constants. The annealing process on the doped samples decreased the dispersion and oscillator energies as well as es. Oppositely, el values increased from 12.52 to 24.45 as a result of larger grain size and less defect density associated with annealing process when T-a is raised from 200 to 400 degrees C, respectively. (C) 2015 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 22
    Citation - Scopus: 23
    Temperature Effects on the Structural and Optical Properties of the Tlinse2xs2(1-x)< Mixed Crystals (x=0.3)
    (Elsevier Science Sa, 2017) Omar, A.; Qasrawi, A. F.; Gasanly, N. M.
    In this work, we have studied the temperature effects on the recrystallization process and on the energy band gap of the TlInSe(2)xS(2(1 - x)) mixed crystals at the critical composition (x = 0.3) where structural phase transition from tetragonal to monoclinic takes place. Remarkable effect which included permanent recrystallization process, enlargements in the monoclinic crystallite size, decreases in the compressing strain and in the dislocation density as well as in the stacking faults and in the energy band gap with increasing temperature were observed. In addition, the temperature dependent energy band gap of the crystal which is investigated in the same temperature range that was used for the recrystallization process revealed that the recrystallization process is associated with energy band gap narrowing. (C) 2017 Elsevier B.V. All rights reserved.