Kayed, Tarek Said

This item is non-discoverable

Kayed, Tarek Said

Name Variants

Kayed, Tarek S.
T.,Kayed
K., Tarek Said
T.S.Kayed
Kayed, Tarek Said
T., Kayed
Tarek Said, Kayed
K.,Tarek Said
Kayed,T.S.
Kayed, TS
Kayed, T. S.
Kayed, TS

Job Title

Doçent Doktor

Full item page

Scholarly Output

24

Articles

21

Citation Count

199

Supervised Theses

0 Scholarly Output Search Results

Now showing 1 - 10 of 24

Citation Count: 11
Microstructural, thermal, and electrical properties of Bi_1.7V_0.3Sr₂Ca₂Ca₃O_x glass-ceramic superconductor
(Wiley-v C H verlag Gmbh, 2004) Kayed, Tarek Said; Erhan, İnci; Aksu, E; Koralay, H; Günen, A; Ercan, I; Cavdar, S; Mathematics; Department of Electrical & Electronics Engineering
A glass-ceramic Bi1.7V0.3Sr2Ca2Cu3Ox superconductor was prepared by the melt-quenching method. The compound was characterized by scanning electron microscopy, x-ray diffraction, differential thermal analysis, current-voltage characteristics, transport resistance measurements, and Hall effect measurements. Two main phases (BSCCO 2212 and 2223) were observed in the x-ray data and the values of the lattice parameters quite agree with the known values for 2212 and 2223 phases. The glass transition temperature was found to be 426 degreesC while the activation energy for crystallization of glass has been found to be E-a = 370.5 kJ / mol. This result indicates that the substitution of vanadium increased the activation energy for the BSCCO system. An offset T-c of 80 K was measured and the onset T-c was 100 K. The Hall resistivity rho(H) was found to be almost field-independent at the normal state. A negative Hall coefficient was observed and no sign reversal of rho(H) or RH could be noticed. The mobility and carrier density at different temperatures in the range 140-300 K under different applied magnetic fields up to 1.4 T were also measured and the results are discussed.
Citation Count: 5
Properties of Se/Inse Thin-Film Interface
(Springer, 2016) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Kayed, T. S.; Elsayed, Khaled A.; Kayed, Tarek Said; Qasrawı, Atef Fayez Hasan; Kayed, Tarek Said; Qasrawı, Atef Fayez Hasan; Kayed, Tarek Said; Department of Electrical & Electronics Engineering; 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: 1
Pseudodielectric Dispersion in As₂se_{3< Thin Films}
(Wiley-v C H verlag Gmbh, 2020) Kayed, Tarek S.; Kayed, Tarek Said; Qasrawi, Atef F.; Qasrawı, Atef Fayez Hasan; Kayed, Tarek Said; Qasrawı, Atef Fayez Hasan; Kayed, Tarek Said; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
Herein, X-ray diffraction, energy dispersive X-ray spectroscopy, and spectral ellipsometry techniques are used to investigate the structural, pseudo-optical, and pseudodielectric properties of arsenic selenide thin films. The stoichiometric films which are prepared by the thermal evaporation technique are found to prefer the amorphous nature of growth. While the pseudoabsorption coefficient spectra display strong absorption bands at 1.84, 1.81, 1.41, and 1.13 eV, the preferred pseudo-optical transitions happen within a direct forbidden energy bandgap of 1.80 eV. In addition, the real part of the pseudodielectric spectra displays three strong resonance peaks at critical energy values of 2.33, 1.90, and 1.29 eV. Modeling of the imaginary part of the pseudodielectric constant spectra in accordance with the Drude-Lorentz approach results in the existence of six linear oscillators. The response of arsenic selenide to elliptically polarized light signals shows that the films exhibit drift mobility, free electron concentration, and plasmon frequency values in the ranges of 0.21-43.96 cm(2) V(-1)s(-1), 1.90-58.0 x 10(19) cm(-3), and 5.8-32.0 GHz, respectively. The optical conductivity parameters for As2Se3 film nominate it as a promising candidate for the fabrication of tunneling diodes suitable for microwaves filtering up to 32.0 GHz and as thin-film transistors.
Citation Count: 3
Effect of Magnetic Field and Γ Irradiation on the Properties of Tl-2212 Superconducting Tape
(Wiley-v C H verlag Gmbh, 2002) Kayed, TS; Kayed, Tarek Said; Ercan, I; Erhan, İnci; Mathematics; Department of Electrical & Electronics Engineering
The critical temperature and critical current of Tl-2212 superconducting sample in the form of a tape have been studied near T-c under magnetic field and gamma irradiation. T-c decreases from 109 to 94 K with increase of magnetic field up to 300 mT. In 77-109 K range, J(c) decreases rapidly in low fields up to around 50 mT followed by a very slow decrease in J(c) up to 300 mT. T-c of the sample did not change up to 100 MR gamma dose and then started to decrease from 109 to 102 K with increase of gamma dose up to 800 MR, most of the change taking place in high doses. The critical currents of the sample decreased steadily with gamma irradiation up to 600 MR after which no further change was noticed.
Citation Count: 4
Optical Characterization of the Mgo/Inse Interface
(Wiley-v C H verlag Gmbh, 2015) Kayed, T. S.; Qasrawı, Atef Fayez Hasan; Qasrawi, A. F.; Elsayed, Khaled A.; Kayed, Tarek Said; Department of Electrical & Electronics Engineering
In this work, a 500nm thick MgO layer deposited on the physically evaporated amorphous InSe thin film substrate is designed as a window for the MgO/InSe terahertz resonators. The optical properties including the reflectance and the dielectric constant dependence on the angle of incidence ((i)), the normal transmittance, and the absorption coefficient of the interface were investigated in the range of approximate to 270-1000THz. It was observed that the total reflectivity of the substrate continuously decreases with increasing (i) in the range of 33-80 degrees. The spectra of InSe and MgO/InSe revealed strong dielectric resonance patterns below 450THz. The energy bands of the direct allowed transitions in InSe film shrunk from 3.90, 2.75, and 1.49eV to 3.71, 2.10, and 0.96eV when MgO was deposited onto the InSe film. By analyzing the dielectric spectra, we were able to determine the static and lattice dielectric constants in addition to the oscillator and dispersion energies. The latter energy increased from 27.43 to 35.84 via interface construction.
Citation Count: 5
Magnetoresistance, Voltage-Current Characteristics, and Hall Effect Measurements of Bulk Mgb₂ Superconductors
(Wiley-v C H verlag Gmbh, 2004) Kayed, TS; Kayed, Tarek Said; Department of Electrical & Electronics Engineering
Bulk MgB2 samples were prepared from the commercially available powder (Alfa-Aesar). One of the samples was used in measuring the transport properties by the DC four-probe technique while the other was used in measuring Hall effect using the van-der-Pauw configuration. From the transport measurements, we noticed that the R-T curves shift to lower temperatures under applied magnetic field without any observed enlargement of the transition width. T-c gradually decreases from 37 K at zero field to 32 K at B = 1.4 T. Our V-I data were found to obey a power law expression V proportional to I-beta(T,I- B). The change of beta with temperature and magnetic field was shown and discussed. R-H is positive under positive applied magnetic field. The 1/R-H linear dependency on T, usually observed in high temperature superconductors, could not be observed in our case. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Citation Count: 2
Characterization of As₂se_{3< Heterojunction Designed for Multifunctional Operations}
(Iop Publishing Ltd, 2021) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Kayed, T. S.; Kayed, Tarek Said; Department of Electrical & Electronics Engineering
In this article, As2Se3/MoO3 heterojunction devices are structurally, compositionally, optically and electrically characterized. The heterojunction devices which are prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar are observed to exhibit amorphous nature of growth. The optical spectrophotometry measurements and analyses on the heterojunction devices revealed a conduction and valence band offsets of values of 2.64 and 4.08 eV, respectively. In addition, the dielectric dispersion and the optical conductivity parametric analyses have shown that the heterojunction could exhibit large drift mobility value up to 73.7 cm(2) V-1 s(-1). From electrical point of view, while the capacitance- voltage curves reveal characteristics of MOSFET devices, the current--voltage curves display tunneling diode characteristics. The features of the As2Se3/MoO3 devices including the band offsets, drift mobility, plasmon frequency, microwave band filtering and MOSFET characteristics make them attractive for use as thin films transistors suitable electrical and optical applications.
Citation Count: 6
Temperature and Magnetic Field Effects on the Carrier Density and Hall Mobility of Boron-Doped Tl-Ba Superconductor
(Elsevier Science Sa, 2005) Kayed, TS; Qasrawı, Atef Fayez Hasan; Qasrawi, AF; Kayed, Tarek Said; Department of Electrical & Electronics Engineering
Boron-doped T1-based superconductor was prepared by adding an amount of 1 wt.% B to the Tl1.8Ba2Ca2.2Cu3Ox, compound. The usual solid-state reaction method has been applied under optimum conditions. The X-ray data of the sample show a tetragonal structure with a high ratio of T1-2223 superconducting phase. The sample showed a transition at 125 K and the zero resistance was observed at 120 K. The magnetic field and temperature effects on the normal state electrical resistivity, carrier density, and Hall mobility have been investigated. Both temperature and magnetic field significantly affect the resistivity behavior. The zero field resistivity was found to vary exponentially with temperature with a slope revealing activation energy of 27.5 meV. When the magnetic field is applied, the resistivity varied up-normally in the temperature region of 160-240 K. The temperature dependent carrier concentration calculated from the Hall coefficient data varied linearly with the applied magnetic field. This effect was attributed to the increase in the hole effective mass upon field increment. The temperature-dependent carrier concentration data at several applied fields were analyzed by the single donor-single acceptor model to obtain the values of effective masses. The temperature and magnetic field dependent normal state Hall mobility was found to be limited by the scattering of acoustic phonons. (c) 2005 Elsevier B.V. All rights reserved.
Citation Count: 4
Band Offsets and Optical Conduction in the Cdse/Gase Interface
(Elsevier Science Bv, 2016) Kayed, T. S.; Qasrawı, Atef Fayez Hasan; Qasrawi, A. F.; Elsayed, Khaled A.; Kayed, Tarek Said; Department of Electrical & Electronics Engineering
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.
Citation Count: 9
Effect of Lithium Doping on the Properties of Tl-Based Superconductors
(Iop Publishing Ltd, 2001) Kayed, TS; Kayed, Tarek Said; Özkan, H; Özkan, Hakan; Gasanly, NM; Department of Electrical & Electronics Engineering
The effects of lithium doping on the formation and properties of the T1-based superconductors have been studied. Lithium atoms up to around 3 mol.% have been added to the oxides of nominal composition Tl1.8Ba2Ca2.2Cu3Ox, and the usual solid-state reaction method has been applied. Lithium additions in the range 0.23-0.29 mol.% increase the fraction of the Tl-2223 phase and significantly improve the critical temperature of the samples. Higher amounts of lithium additions diminish the Tl-2223 phase, reduce the fraction of the Tl-2212 phase, and cause separate non-superconducting phases to be formed.

Kayed, Tarek Said

Name Variants

Job Title

Email Address

ORCID ID

Scopus Author ID

Turkish CoHE Profile ID

Google Scholar ID

WoS Researcher ID

Scholarly Output

24

Articles

21

Citation Count

199

Supervised Theses

0

Filters

Settings

Sort By

Results per page

Scholarly Output Search Results