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Article Citation - WoS: 3Citation - Scopus: 3Current 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 EngineeringAu/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.Article Citation - WoS: 3Citation - Scopus: 3Effect of Ionic Substitution on the Structural, Dielectric and Electrical Properties of Bismuth Zinc Niobate Ceramics(Korean Assoc Crystal Growth, inc, 2012) Qasrawi, A. F.; Abu Je'ib, Hussein A.; Mergen, A.; Department of Electrical & Electronics EngineeringThe effects of tin substitution on the structural, dielectric and electrical properties of the Bi1.5Zn0.92Nb1.5O6.92 pyrochlore ceramics have been investigated. Tin atoms was substituted in the A (Bi1.5Zn0.46)-site instead of zinc and in the B ((Zn0.46Nb1.5)-site instead of niobium in accordance to the chemical formulae Bi1.5Zn0.92Nb1.5-xO6.92-x/2 and (Bi1.5-x/3Zn0.46-3x/2Snx)(Nb1.5Zn0.46)O-6.92, for 0.00 <= x <= 0.40 and 0.00 <= x <= 0.60, respectively. A relative single phase formation of the structures was possible for x values less than 0.25 and less than 0.10. Pronounced tunability in the dielectric constant values associated with very low dielectric loss are obtainable by Sn substitution. Furthermore, a frequency invariant but linearly varying temperature dependent dielectric constant is observed. The electrical conductivity decreased by two and one order of magnitude for the A and B-site substitutions, respectively. The temperature-dependent conductivity analysis in the temperature region of 300-500 K, reflected the existence of shallow and deep impurity energy levels being created by the doping process.Article Citation - WoS: 2Citation - Scopus: 2Effect 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 EngineeringIn 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.Article Driving Electric Field Effects on the Space Charge Limited Photocurrent of In6s7<(Natl inst Optoelectronics, 2013) Qasrawi, A. F.; Al-Balshi, Madleen A.; Gasanly, N. M.; Department of Electrical & Electronics EngineeringA new type of photovoltaic materials, which are designed on the base of In6S7 single crystals using silver and gold metals to construct Ag/In6S7/Au point contacted photocells, are reported and discussed. The influence of the driving electric field on the performance of the device was tested. The current density-electric field dependence curve reflected a space charge limited photocurrent effect being dominant in the field region of 1.0-4.3 V/cm. In addition, the In6S7 photocell short circuit and loaded current dependencies on the excitation intensity were measured. The short circuit current was observed to exhibit exponential trap distribution effect and supralinear recombination at low and high illumination intensities, respectively. The device displays a current density of 0.5 mA/cm(2) for excitation intensity of 76 klux. When loaded, it displayed a stable power dissipation curve. Such behavior reflects the novelty of these types of cells for future application.Article Citation - WoS: 10Citation - Scopus: 9Tunable Au/Ga2< Varactor Diodes Designed for High Frequency Applications(Natl inst R&d Materials Physics, 2017) Al Garni, S. E.; Qasrawi, A. F.; Department of Electrical & Electronics EngineeringIn this work, the design and characterization of Au/Ga2S3/Yb Schottky barrier is investigated by means of transmittance electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), capacitance spectroscopy, capacitance (C)-voltage (V) characteristics and impedance spectroscopy techniques. The design of the energy band diagram of the amorphous Au/Ga2S3 interface revealed a theoretical energy barrier height (q phi(b)) and built in voltage (qV(bi)) of 2.04 and 1.88 eV, respectively. Experimentally, the qV(bi) was observed to be sensitive to the applied signal frequency. In addition, the capacitance spectra which were studied in the range of 10-1800 MHz, revealed resonance and antiresonance biasing dependent signal oscillations associated with negative capacitance values. On the other hand, impedance spectroscopy analysis revealed band pass/reject filtering properties in all the studied frequency range. The device exhibited a return loss, voltage standing wave ratio and power efficiency of 16.7 dB, 1.3 and 98.3% at 1400 MHz, respectively.Article Citation - WoS: 5Citation - Scopus: 5Formation and Negative Capacitance Effect in Au/Bi2< Heterojunctions Designed as Microwave Resonators(Natl inst R&d Materials Physics, 2018) Al Garni, S. E.; Qasrawi, A. F.; Department of Electrical & Electronics EngineeringIn this article, the physical design, energy band diagram, temperature dependent electrical resistivity and the impedance spectroscopy measurements of the Au/Bi2O3/ZnS/Ag isotype heterojunction devices are reported. The devices are prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar. Structural, compositional and morphological studies has shown the presence of an expansion in the lattice of Bi2O3 associated with increased strain and dislocation density and decreased grain size as a result of ZnS interfacing. The design of the band diagram indicated that the formed heterojunction exhibit large valence and conduction band offsets that forces charge accumulation at the interface. The Au/Bi2O3/ZnS/Ag device displays negative capacitance (NC) effect in the frequency domain of 0.01-1.50 GHz. The NC effect is interrupted by a resonance-antiresonance phenomenon in the frequency domain of 0.90-1.07 GHz. In addition to the NC effects, the device under study exhibited reflection coefficient and return loss spectra that nominate it for use as microwave cavities or as low pass band filters.
