Browsing by Author "Qasrawi, A. F."

Now showing 1 - 20 of 165

Citation - WoS: 9
Absorption and Optical Conduction in Inse/Znse Thin Film Transistors
(World Scientific Publ Co Pte Ltd, 2016) Al Garni, S. E.; Qasrawi, A. F.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
In this work, (n)InSe/(p)ZnSe and (n)InSe/(p)ZnSe/(n)InSe heterojunction thin film transistor (TFT) devices are produced by the thermal evaporation technique. They are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy and optical spectroscopy techniques. While the InSe films are found to be amorphous, the ZnSe and InSe/ZnSe films exhibited polycrystalline nature of crystallization. The optical analysis has shown that these devices exhibit a conduction band offsets of 0.47 and valence band offsets of 0.67 and 0.74 eV, respectively. In addition, while the dielectric spectra of the InSe and ZnSe displayed resonance peaks at 416 and 528 THz, the dielectric spectra of InSe/ZnSe and InSe/ZnSe/InSe layers indicated two additional peaks at 305 and 350 THz, respectively. On the other hand, the optical conductivity analysis and modeling in the light of free carrier absorption theory reflected low values of drift mobilities associated with incident alternating electric fields at terahertz frequencies. The drift mobility of the charge carrier particles at femtoseconds scattering times increased as a result of the ZnSe sandwiching between two InSe layers. The valence band offsets, the dielectric resonance at 305 and 350 THz and the optical conductivity values nominate TFT devices for use in optoelectronics.
Citation - WoS: 5
Citation - Scopus: 5
Acoustic Phonons Scattering Mobility and Carrier Effective Mass in In₆s_{7< Crystals}
(Elsevier Science Sa, 2006) Qasrawi, A. F.; Gasanly, N. M.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
Systematic dark electrical resistivity and Hall coefficient measurements have been carried out in the temperature range of 170-320 K on n-type In6S7 crystals. The analysis of the electrical resistivity and carrier concentration reveals the intrinsic type of conduction with an average energy band gap of similar to 0.75 eV The carrier effective masses of the conduction and valence bands were calculated from the intrinsic temperature-dependent carrier concentration data and were found to be 0.565m(0) and 2.020m(0), respectively. The temperature-dependent Hall mobility was observed to follow the mu alpha T-3/2 law and was analyzed assuming the domination of acoustic phonons scattering. The acoustic phonons scattering mobility was calculated from the crystal's structural data with no assumptions. The experimental Hall mobility data of In6S7 crystals coincides with the theoretical acoustic phonons scattering mobility data with acoustic deformation potential of 6.4 eV. (c) 2006 Elsevier B.V. All rights reserved.
Citation - WoS: 6
Citation - Scopus: 6
Al/Cdse Resonant Tunneling Thin Film Transistors
(Elsevier Science Bv, 2017) Qasrawi, A. F.; Kayed, T. S.; Elsayed, Khaled A.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
An Al/CdSe/GaSe/C thin film transistor device was prepared by the physical vapor deposition technique at a vacuum pressure of 10(-5) mbar. The x-ray diffraction measurements demonstrated the polycrystalline nature of the surface of the device. The de current-voltage characteristics recorded for the Al/CdSe/C and Al/CdSe/GaSe/C channels displayed a resonant tunneling diode features during the forward and reverse voltage biasing, respectively. In addition, the switching current ratio of the Al/CdSe/C increased from 18.6 to 9.62x10(3) as a result of the GaSe deposition on the CdSe surface. Moreover, the alternating electrical signal analyses in the frequency range of 1.0 MHz to 1.8 GHz, showed some remarkable properties of negative resistance and negative capacitance spectra of the AVCdSe/GaSe/C thin film transistors. Two distinct resonance-antiresonance phenomena in the resistance spectra and one in the capacitance spectra were observed at 0.53, 1.04 and 1.40 GHz for the Al/CdSe/C channel, respectively. The respective resonating peak positions of the resistance spectra shift to 0.38 and 0.95 GHz when GaSe is interfaced with CdSe. These features of the thin film transistors are promising for use in high quality microwave filtering circuits and also for use as ultrafast switches.
Citation - WoS: 7
Citation - Scopus: 9
Analysis of the Hall Effect in Tlgate₂ Single Crystals
(Iop Publishing Ltd, 2009) Qasrawi, A. F.; Gasanly, N. M.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
The electrical resistivity and Hall coefficient of p-type TlGaTe2 crystals were measured in the temperature range of 110-320 K. The electrical resistivity, charge carrier density and Hall mobility data for the crystals have been analyzed by means of existing theories and models to determine the extrinsic energy levels, the carrier effective mass, the donor and acceptor concentrations and the dominant scattering mechanism in the crystal as well. The analysis of the temperature-dependent electrical resistivity recorded parallel and perpendicular to the crystal's axis ( c-axis) reflected the existence of energy levels located at 0.26 and at 0.20 eV, respectively. The difference of these two energy levels is due to crystal anisotropy. The energy level at 0.26 eV was found to represent an acceptor level, as confirmed from Hall data analysis. The temperature dependence of the carrier density was analyzed by using the single-donor-single-acceptor model. The latter analysis revealed the carrier effective mass and the acceptor and donor concentrations as 0.73m(0), 4.10 x 10(17) cm(-3) and 1.20 x 10(17) cm(-3), respectively. The Hall mobility of TlGaTe2 is found to be limited by the scattering of hole-acoustic phonon interactions. The calculated theoretical mobility fits to the experimental one under the condition that the acoustic deformation potential is 11.0 eV, which is the energy position of the top of valence band maximum that is formed by the Te 5s states.
Citation - WoS: 2
Citation - Scopus: 2
Anisotropic Electrical and Dispersive Optical Parameters in Ins Layered Crystals
(Pergamon-elsevier Science Ltd, 2010) Qasrawi, A. F.; Gasanly, N. M.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
The anisotropy effect on the current transport mechanism and on the dispersive optical parameters of indium monosulfide crystals has been studied by means of electrical conductivity and polarized reflectance measurements along the a-axis and the b-axis, respectively. The temperature-dependent electrical conductivity analysis in the range 10-350 K for the a-axis and in the range 30-350 K for the b-axis revealed the domination of the thermionic emission of charge carriers and the domination of variable range hopping above and below 100 K, respectively. At high temperatures (T > 100 K) the conductivity anisotropy, s, decreased sharply with decreasing temperature following the law s proportional to exp(-E(s)/kT). The anisotropy activation energy, E(s), was found to be 330 and 17 meV above and below 220 K, respectively. Below 100 K, the conductivity anisotropy is invariant with temperature. in that region, the calculated hopping parameters are altered significantly by the conductivity anisotropy. The optical reflectivity analysis in the wavelength range 250-650 nm revealed a clear anisotropy effect on the dispersive optical parameters. In particular, the static refractive index, static dielectric constant, lattice dielectric constant, dispersion energy and oscillator energy exhibited values of 2.89, 8.39, 19.7, 30.02 eV and 4.06 eV, and values of 2.76, 7.64, 25.9, 22.26 eV and 3.35 eV for light polarized along the a-axis and the b-axis, respectively. (C) 2009 Elsevier Ltd. All rights reserved.
Citation - WoS: 27
Citation - Scopus: 28
Annealing Effects on the Structural and Optical Properties of Agin₅s_{8< Thin Films}
(Elsevier Science Sa, 2008) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
Due to its importance as a perspective material for application in optoelectronic semiconductor devices, the thermal annealing effects on the structural and optical properties of the as-grown vacuum evaporated AgIn5S8 thin films have been investigated. The X-ray data analysis have shown that these films are polycrystalline in nature and exhibit better crystallization with increasing crystallite size and slightly, decreasing unit cell lattice parameter as annealing temperature is raised from 450 to 600 K. The optical energy band gap for the as-grown and thermally annealed films is found to be of direct allowed transitions type. The energy band gap exhibited values of 1.78, 1.74 and 1.62 eV as the samples were annealed at, 450 and 600 K, respectively. This indicates the ability of altering the band gap values of this material by the thermal annealing process. The structural and optical features seem to be suitable for semiconductor device production such as solar cell converters, which has successfully been fabricated by others, metal-insulator-semiconductor (MIS) and metal - oxide - semiconductor (MOS) devices, as well. (c) 2007 Elsevier B.V. All rights reserved.
Citation - WoS: 3
Citation - Scopus: 4
Au/As_{2< Schottky Barriers Designed as Multifunctional Devices}
(Ieee-inst Electrical Electronics Engineers inc, 2020) Al Harbi, S. R.; Qasrawi, A. F.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
In this article, Au/As2Se3/Ag/As2Se3/Yb Schottky barriers are formed and characterized. The devices prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar are observed to exhibit metal-induced crystallization process when coated onto Au substrates. Electrically, the arsenic selenide-based Schottky devices exhibited typical metal-oxide-semiconductor (MOS) characteristics with a built-in potential of 0.17 eV. The device shows resonance-antiresonance switching, negative capacitance (NC) effect, and high to low conductance switching features in the frequency domain of 10-1800 MHz. In addition, measurement of the impedance, amplitude of reflection coefficient, return loss (L-r), and voltage standing wave ratio (VSWR) spectra in the same domain have shown that the Au/As2Se3/Ag/As2Se3/Yb Schottky barriers display band stop features at 1180 MHz. The L-r and VSWR values at this critical frequency are 29.1 dB and 1.1, respectively. The electrical characterizations of the Au/As2Se3/Ag/As2Se3/Yb MOS devices have confirmed their suitability for use as parasitic capacitance cancellers, noise reducers, and as switching clock with selective switching time scales of switching delay time less than 0.40 ns.
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.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
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 - WoS: 3
Citation - Scopus: 3
Characterization of Ag/Tlinse_{2< Structure}
(Wiley-blackwell, 2011) Qasrawi, A. F.; Gasanly, N. M.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
In this work, the current voltage characteristics of Ag/TlInSe2/Ag and In/TlInSe2/In structures, the incident light intensity and time dependencies of photocurrent as well as the response time-illumination intensity dependence of Ag/TlInSe2/Ag structures have been studied. For bias voltages larger than 1200. and 4.0 V, the current injection was found to be space charge limited and was assigned to the existing of deep and shallow hole traps being located at 210 and 16 meV for Ag and In-contacted samples, respectively. While indium-contacted samples show S-shaped I-V dependence above bias voltage of 10.0V, silver contacted samples does not show this behavior even at 200.0 V. For the Ag/TlInSe2/Ag structure, photocurrent was observed to exhibit stable values in a very short period of time. The device response time decreases with increasing illumination intensity, it exhibits a value of 0.13 s at incident light intensity of 53.6 mW cm(-2). The decrement in response time with increasing illumination intensity is associated with an increment in photocurrent at the same ratio. The ohmic behavior up to high voltages (120 V), the fast response time and the large spatial photocurrent make the Ag/TlInSe2/Ag structure promising IR detectors. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Citation - WoS: 3
Citation - Scopus: 3
Characterization of As₂se_{3< Heterojunction Designed for Multifunctional Operations}
(Iop Publishing Ltd, 2021) Qasrawi, A. F.; Kayed, T. S.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
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 - WoS: 11
Citation - Scopus: 12
Characterization of Au/As_{2< Hybrid Devices Designed for Dual Optoelectronic Applications}
(Elsevier, 2020) Kayed, T. S.; Qasrawi, A. F.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
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 - WoS: 4
Citation - Scopus: 4
Characterization of Bi₂o_{3< Heterojunctions Designed for Visible Light Communications}
(Iop Publishing Ltd, 2019) Al Garni, S. E.; Qasrawi, A. F.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
In the current work, the structural, morphological and optical properties of the Bi2O3/ZnS heterojunctions as visible light communication (VLC) technology element are explored. Bismuth oxide layers of thicknesses of 200 nm are used as substrate to evaporate ZnS films of thicknesses of 500 nm by the thermal evaporation technique under vacuum pressure of 10(-5) mbar. The heterojunction devices are studied by the x-ray diffraction, scanning electron microscopy, optical spectrophotometry and microwave spectroscopy techniques. The Bi2O3/ZnS heterojunctions are found to form a highly strained structure with extremely large lattice mismatches. By the strained structure and with the valence and conduction band offsets that exhibit values of 1.04 and 0.41 eV, respectively, it was possible to enhance the light absorbability of ZnS by 459 times at 3.10 eV. In addition, the dielectric constant spectra of the device display a linear and nonlinear optical properties below and above 1.94 eV, respectively. Moreover, the optical conductivity parameters including the drift mobility and plasmon frequency and the cutoff frequency spectra of an area of 0.50 cm(2) of Bi2O3/ZnS interfaces have shown the ability of using these heterojunction devices as light signal receivers that attenuate signals at terahertz frequencies in the range of 0.27-1.00 THz. As an additional demonstration, the Bi2O3/ZnS heterojunction devices were subjected to a microwave signal propagation in the frequency domain of 0.01-2.90 GHz. The device performed as band filters at gigahertz frequencies.
Citation - WoS: 1
Citation - Scopus: 1
Characterization of T1ins1.8se0.2 as Advanced Functional Crystals
(Elsevier Sci Ltd, 2018) Qasrawi, A. F.; Atatreh, Areen A. M.; Gasanly, N. M.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
In this work, selenium doped TlInS1.8Se0.2 crystals are used to fabricate multifunctional devices that can handle more than one duty at a time. After revealing the morphological, compositional, structural and optical properties of the doped crystal, it is sandwiched between Ag and carbon metals. The crystals are characterized by means of ultraviolet-visible light spectrophotometry, impedance spectroscopy and illumination dependent current-voltage characteristics techniques. While the optical spectroscopy allowed determining the energy band gap of the crystals as well as the optical conductivity in the terahertz frequency domain, the impedance spectroscopy allowed identifying the conductance and reflectance spectra in the gigahertz frequency domain. The two techniques reveal promising characteristics presented by optical switching at 2.20 eV and band pass filtering properties in mega/gigahertz frequency domains. On the other hand, the analysis of the current (I)- voltage (V) characteristics which are recorded in the dark and under photoexcitation of unfiltered tungsten light in the light power range of 25-130 mW, revealed light intensity dependent rectifying properties. Particularly, the modeling of the experimental I-V curves in accordance with the Richardson Schottky and Chueng's theoretical approaches have shown that the Schottky diode ideality factor, series resistance and barrier height decreases with increasing light power. Such behavior indicates wide tunability of the device when used as photosensors. With the features presented by small size, photosensitivity, gigahertz/terahertz spectral responses, the device can be promising element for use in visible light and microwave communications.
Citation - WoS: 6
Citation - Scopus: 6
Characterization of the A1/Ge/In₂Se₃/Ga₂S₃/Al hybrid tunneling barriers designed for Gigahertz/Terahertz applications
(Elsevier Science Sa, 2018) Qasrawi, A. F.; Omareya, Olfat A.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
In the current work, we report the design and performance of a tunneling amorphous thin film hybrid device made of Ge/In2Se3/Ga2S3 sandwiched between two aluminum thin films. Each of the stacked semiconducting layers are of 200 nm thicknesses. The hybrid device which is composed of a p-n junction between two Schottky shoulders is designed to have two valence band offsets of 0.59 and 0.84 eV at the Ge/In2Se3 and at In2Se3/Ga2S3 interfaces, respectively The offsets which caused two quantum confinements forces the device to exhibit field effect assisted thermionic and thermionic transport mechanisms under the reverse and forward biasing conditions, respectively. When an alternating current signal is imposed between the terminals of the device, the device conducted by the quantum mechanical tunneling of charge carriers and by the correlated barrier hopping above and below 0.180 GHz, respectively. The hybrid structure are also observed to exhibit series and parallel resonance at the switching frequency between the two conduction mechanisms. It also exhibited negative differential capacitance effect in the frequency domain of 0.18-1.80 GHz. For the Al/Ge/In(2)Se3/Ga2S3/Al hybrid structure the microwave cutoff frequency reached 100 GHz. The latter value is promising as it indicates the ability of using the device as fast switches and microwave/Tera wave traps.
Citation - WoS: 2
Citation - Scopus: 2
Characterization of the Mgo/Gase_{0.5< Heterojunction Designed for Visible Light Communications}
(Elsevier Sci Ltd, 2015) Qasrawi, A. F.; AlGarni, S. E.; Gasanly, N. M.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
In this study an optoelectronic design is reported and characterized. The device is made of p-type MgO solved in sodium silicate binder and n-type GaSe0.5S0.5 heterojunction. It is described by means of X-ray diffraction, optical absorption and reflection in the incident light wavelength range of 190-1100 nm and by means of dark and 406 nm laser excited current (I)-voltage (V) characteristics. The optical reflectance was also measured as a function of angle of incidence of light in the range of 35-80. The structural analysis revealed no change in the existing phases of the device composers. In addition, it was observed that for pure sodium silicate and for a 67% content of MgO solved in sodium silicate binder (33%), the heterojunction exhibits a valence band shift of 0.40 and 0.70 eV, respectively. The painting of MgO improved the light absorbability significantly. On the other hand, the angle-dependent reflectance measurements on the crystal displayed a Brewster condition at 70. The MgO/ GaSe0.5S0.5 heterojunction exhibited no Brewster condition when irradiated from the MgO side. Moreover, for the crystal and the MgO/ GaSe0.5S0.5 heterojunction, the dielectric spectral analysis revealed a pronounced increase in the quality factor of the device. The I-V characteristics of the device revealed typical optoelectronic properties with high photo-response that could amplify the dark current 24 times when irradiated with 5 mW power laser light. The structural, optical, dielectric and electrical features of the MgO/GaSe0.5S0.5 heterojunction nominate it for use in visible light communication technology. (C) 2015 Elsevier Ltd. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 1
Characterization of the Nanosandwiched Ga₂s_{3< Interfaces as Microwave Filters and Thermally Controlled Electric Switches}
(Elsevier Gmbh, 2018) Alharbi, S. R.; Nazzal, Eman O.; Qasrawi, A. F.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
In this work, an indium layer of 50 nm thicknesses is sandwiched between two 500 nm thick Ga2S3 layers. The effect of indium nansandwiching on the composition, structure, morphology, light absorbability, capacitance and reactance spectra, and temperature dependent electrical conductivity of the Ga2S3 films are investigated by means of X-ray diffraction, scanning electron microscopy, energy dispersion X-ray spectroscopy, Raman spectroscopy, visible light spectrophotometry, impedance spectroscopy and current voltage characteristics. While the nansandwiched films are observed to exhibit an amorphous nature of structure with indium content of Owing to the nucleation mechanisms that take place during the film growth, the accumulation of some unit cells in groups to form grains should be a significant reason for the existence of many different sizes of grains in the nanosand-wiched films (Alharbi and Qasrawi, 2016). 0, the Raman spectra displayed three vibrational modes at 127.7,145.0 and 274.3 cm(-1). It was also observed that the indium insertion in the structure of the Ga2S3 shrinks the energy band gap by 0.18 eV. The nanosandwiched films are observed to exhibit a semiconductor metal (SM) transition at 310 K. The SM transition is associated with thermal hysteresis that exhibited a maximum value of 16% at 352 K. This behavior of the nanosandwiched films nominate it for use as thermally controlled electric switches. In addition, the impedance spectral analysis in the range of 10-1800 MHz has shown a capacitance tunability of more than 70%. The measurements of the wave trapping property displayed a bandpass/reject filter characteristics above 1.0 GHz which allow using the Ga2S3/In/Ga2S3 thin films as microwave resonator. (C) 2017 Elsevier GmbH. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 1
Cobalt Doping Effects on the Mechanical and Electrical Parameters of Bi_1.5zn_{0.92< Solid Solution}
(indian Ceramic Soc, 2014) Qasrawi, A. F.; Jaradat, Haneen N. M.; Mergen, A.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
The cobalt doping effects on the lattice constant, strain, grain size, dislocation density and electrical conduction are investigated by means of X-ray diffraction and electrical resistivity measurements on the Bi1.5Zn0.92Nb1.5-xCoxO6.92-x (x=0.03-0.20) ceramics, respectively. Increasing cobalt content sharply increases compressing strain and dislocation density and decreases both the lattice constant and the grain size of the pyrochlore. At a doping content of 0.05 new minor phase of ZnO appears. The ZnO grains increase with increasing cobalt content. When the cobalt doping is repeated in accordance with the formula Bi1.5Zn0.92Nb1.5-xCoxO6.92-x, a single phase pyrochlore is obtained with cobalt content up to 0.10. The electrical resistivity analysis reflects increasing activation energy with increasing cobalt content. The cobalt creates an impurity level in the energy gap of the pyrochlore that shifts towards the mid gap converting the extrinsic nature of conductivity to intrinsic at a cobalt content of 0.10.
Citation - WoS: 4
Citation - Scopus: 4
Crystal Data and Indirect Optical Transitions in Tl₂ingase_{4< Crystals}
(Pergamon-elsevier Science Ltd, 2008) Qasrawi, A. F.; Gasanly, N. M.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
The room temperature crystal data and the optical properties of the Bridgman method grown Tl2InGaSe4 crystals are reported and discussed. The X-ray diffraction technique has revealed that Tl2InGaSe4 is a single phase crystal of monoclinic structure. The unit cell lattice parameters, which were recalculated from the X-ray data, are found to be a = 0.77244 nm, b = 0.64945 nm, c = 0.92205 nm and beta = 95.03 degrees. The temperature dependence of the optical band gap of Tl2InGaSe4 single crystal in the temperature region of 290-500 K has also been investigated. The absorption coefficient was calculated from the transmittance and reflectance data in the incident photon energy range of 1.60-2.10 eV. The absorption edge is observed to shift toward lower energy values as temperature increases. The fundamental absorption edge corresponds to indirect allowed transition energy gap of 1.86 eV that exhibited a temperature coefficient gamma = -3.53 x 10(-4) eV/K. (C) 2007 Elsevier Ltd. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 3
Crystal Data and Some Physical Properties of Tl₂ingate_{4< Crystals}
(Wiley-v C H verlag Gmbh, 2007) Qasrawi, A. F.; Gasanly, N. M.; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
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 - WoS: 3
Citation - Scopus: 3
Current Transport Mechanism in Au-p-mgo-ni Schottky Device Designed for Microwave Sensing
(Natl inst Optoelectronics, 2016) Qasrawi, A. F.; Khanfar, H. K.; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
Au/MgO/Ni back to back Schottky tunnelling barriers are designed on the surface of an MgO thin layer and are electrically characterized. The current voltage curve analysis has shown that thermionic emission, field effect thermionic (FET) emission and space charge limited current are dominant transport mechanism in distinct biasing regions. It was shown that, while the device is reverse biased with voltages less than 0.31 V, it conducts by tunnelling (FED though an energy barrier of 0.88 eV with a depletion region width of 15.7 nm. As the voltage exceeds 0.46 V, the tunnelling energy barrier is lowered to 0.76 eV and the depletion region widens and arrives at the reach-through running mode. The device was tested in the microwave electromagnetic power range that extends from Bluetooth to WLAN radiation levels at oscillating frequencies of 0.5 and 2.9 GHz. In addition, a low power resonating signal that suits mobile data is superimposed in the device. It was observed that the Au/MgO/Au sensors exhibit a wide tunability range via voltage biasing or via frequency control. The signal quality factor is 3.53 x 10(3) at 2.9 GHz. These properties reflect applicability in microwave technology as wireless and connectorized microwave amplifiers, microwave resonators and mixers.