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Article Citation - WoS: 5Citation - Scopus: 5Structural and Electrical Characterizations of the as Grown and Annealed Au/Mοo3< Bandpass Filters(Wiley, 2019) Khanfar, Hazem K.; Qasrawi, Atef; Daraghmeh, Masa; Abusaa, MuayadIn this work, the structural, morphology, and electrical properties of two 500 nm thick molybdenum trioxide layers that are sandwiched with indium slab of thickness of 200 nm (MoO3/In/MoO3 [MIM]) to form a bandpass filter are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and impedance spectroscopy techniques, respectively. The MIM films which coated onto Au thin film substrates by the thermal evaporation technique under vacuum pressure of 10(-5) mbar was post annealed at 250 degrees C in air atmosphere. While the XRD analysis revealed polycrystalline hexagonal lattice structure of the Au/MLM samples, the SEM and EDS analysis displayed grains of sizes of 350 nm and stoichiometric structure of MoO3. Electrically, indium layer which caused n-type conduction with donor level of 299 meV, forced the material to exhibit negative capacitance (NC) effect at high frequencies (above 1.1 GHz). The impedance spectroscopy which was recorded in the frequency domain of 0.01 to 1.80 GHz, also revealed low pass and high pass filters characteristics in the low and high frequency domains, respectively. The annealing of the Au/MIM samples, decreased the crystallite and grain sizes and increased the microstrain, the defect density and the stacking faults. Small amount of excess oxygen and some indium deficiency are observed upon annealing. In addition, the annealing shifted the donor level closer to the bottom of the conduction band and inverted the NC effect from high to low frequency regions. The study indicates the applicability of the Au/MIM/C structures as microwave cavities and parasitic capacitance cancellers in electronic circuits.Article Citation - WoS: 3Citation - Scopus: 3Analysis of the Junction Properties of C/Gase0.5< Back-To Schottky-Type Photodetectors(Ieee-inst Electrical Electronics Engineers inc, 2015) Khanfar, Hazem K.; Qasrawi, Atef F.; Gasanly, Nizami M.In this paper, a C/GaSe0.5S0.5/C metal-semiconductor-metal photodetector is suggested and described. The device is explored by means of current-voltage and capacitance-voltage (C-V) characteristics under different photoexcitation intensities. It was observed that the design of the back-to-back Schottky device has reduced the dark current of the normal Ag/GaSe0.5S0.5/C Schottky diode by 13 times and increased the photosensitivity from 3.8 to similar to 2.1x10(3). The device exhibited a barrier height of 0.842 eV in the dark. The barrier height is reduced via photoexcitation. In addition, the C/GaSe0.5S0.5/C device exhibited an ON/OFF switching property from low injection OFF to high injection ON at specific biasing voltages. This voltage decreased with the increasing illumination intensity. On the other hand, the C-V characteristics of the device, which was recorded for an ac input signal with 100 MHz at different levels of photoexcitation shifted up when the intensity of light was increased. When the same measurement was repeated at signal frequency of 1.6 GHz, the C-V characteristics reflected a different level of capacitance response. These features of C/GaSe0.5S0.5/C photodetectors nominate the device to be used as multipurpose optical switches being suitable to store different levels of electromagnetic energy at microwave frequencies.Article Citation - WoS: 2Citation - Scopus: 2Post Annealing Effects on the Structural and Optical Properties of Moo3 Sandwiched With Indium Slabs(Iop Publishing Ltd, 2019) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Kmail, Haifaa K.; AbuSaa, M.; Khanfar, Hazem K.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringMolybdenum trioxide thin films are prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar through insertion of indium slabs of thickness of 200 nm between layers of MoO3 and annealing the produced films in the air atmosphere at 250 degrees C for one hour. The films are studied by means of x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, and optical spectrophotometry techniques. The structure of the films is found to be composed monoclinic MoO3, tetragonal indium and cubic In2O3. The phase percentage of In2O3 in the films increased to 26.3% upon annealing at 250 degrees C. The annealing process increased the microstrain, the defect density, the oxygen atomic content and lowered the crystallites and grains sizes in the films. Optically, two energy band gaps of values of 3.20 and 1.70 eV were detected for the MoO3/In/MoO3 system. In addition, nonlinear dielectric response associated with wide range of tunability in the dielectric constant value, in the optical conductivity and in the terahertz cutoff frequency was observed in the near IR spectral range. The annealing of the samples improved the nonlinearity in these parameters and make MoO3/In/MoO3 system more appropriates for optoelectronic technology applications as terahertz cavities and frequency convertors.Article Citation - WoS: 40Citation - Scopus: 42Design and Electrical Performance of Cds/Sb2< Tunneling Heterojunction Devices(Iop Publishing Ltd, 2018) Khusayfan, Najla M.; Qasrawi, A. F.; Khanfar, Hazem K.In the current work, a tunneling barrier device made of 20 nm thick Sb2Te3 layer deposited onto 500 nm thick CdS is designed and characterized. The design included a Yb metallic substrate and Ag point contact of area of 10(-3) cm(2). The heterojunction properties are investigated by means of x-ray diffraction and impedance spectroscopy techniques. It is observed that the coating of the Sb2Te3 onto the surface of CdS causes a further deformation to the already strained structure of hexagonal CdS. The designed energy band diagram for the CdS/Sb2Te3 suggests a straddling type of heterojunction with an estimated conduction and valence band offsets of 0.35 and 1.74 eV, respectively. In addition, the analysis of the capacitance-voltage characteristic curve revealed a depletion region width of 14 nm. On the other hand, the capacitance and conductivity spectra which are analyzed in the frequency domain of 0.001-1.80 GHz indicated that the conduction in the device is dominated by the quantum mechanical tunneling in the region below 0.26 GHz and by the correlated barrier hopping in the remaining region. While the modeling of the conductivity spectra allowed investigation of the density of states near Fermi levels and an average scattering time of 1.0 ns, the capacitance spectra exhibited resonance at 0.26 GHz followed by negative differential capacitance effect in the frequency domain of 0.26-1.8 GHz. Furthermore, the evaluation of the impedance and reflection coefficient spectra indicated the usability of these devices as wide range low pass filters with ideal values of voltage standing wave ratios.Article Citation - WoS: 11Citation - Scopus: 11Design and Applications of Al/Inse Hybrid Device(Ieee-inst Electrical Electronics Engineers inc, 2015) Qasrawi, Atef F.; Khanfar, Hazem K.In this paper, a hybrid device made of Ag/BN Schottky barrier and anisotype InSe/BN heterojunction is designed and characterized. The design of the energy band diagram of the device revealed a valance band splitting at the InSe/BN interface and a barrier height at the Ag/BN junction of 3.04 and 6.49 eV, respectively. These parameters which were designed to force current conduction by tunneling were experimentally confirmed by the dark I-V characteristics which revealed an electric field assisted tunneling process. The hybrid device exhibited high/low current switching property at Vs = 2.60 V when forward biased. When the device was exposed to 850-nm lasers light, Vs regularly increased with increasing light power indicating the applicability of these devices as IR photodetectors. In addition, when it was used as capacitor and depleted with signal of frequency of 0.1 GHz and varying amplitude it showed good energy storing property with a quality factor of similar to 200. On the other hand, when the hybrid device was used as microwave resonator it behaves like bandstop filter that blocks signals of various notch frequencies in the range of 1.58-2.30 GHz. The features of the device are promising as they indicate the applicability of the Al/InSe/BN/Ag in communication technology.Article Citation - WoS: 4Citation - Scopus: 5Gd and Tb Doping Effects on the Physical Properties of Nd2sn2<(Elsevier Sci Ltd, 2018) Saleh, Adli A.; Hamamera, Hanan Z.; Khanfar, Hazem K.; Qasrawi, A. F.; Yumusak, G.In the current study, we report the light doping effects of the gadolinium and the terbium on the structural, morphological, optical and electrical properties of Nd2Sn2O7 pyrochlore ceramics. The pyrochlore which is prepared by the conventional solid state reaction technique is analyzed by means of scanning electron microscopy, energy dispersive X-ray analyzer, X-ray diffraction, ultraviolet- visible light spectrophotometry and temperature dependent current -voltage characteristics techniques. It is found that even though the doping content of both metals is low (2%), they significantly alter the physical properties of the pyrochlore. Particularly, it is observed that, these two doping agents increases the lattice parameter and strain and reduces the crystallite size and dislocation density. Optically, the effect of Gd doping on shrinking the energy band gap value of the Nd(2)Sn(2)O(7 )pyrochlore ceramic is more pronounced than that of Tb. On the other hand, the electrical investigations have shown that while the Gd make the pyrochlore exhibit p-type conductivity through forming shallow acceptor levels, the Tb forces n-type conductivity by forming deep donor levels below the conduction band edge. Such acceptor and donor impurity levels increases the electrical conductivity of the Nd(2)Sn(2)O(7 )pyrochlore ceramics by 390 and 58 times, respectively.Article Citation - WoS: 26Citation - Scopus: 27Impact of Yb, In, Ag and Au Thin Film Substrates on the Crystalline Nature, Schottky Barrier Formation and Microwave Trapping Properties of Bi2o3< Films(Elsevier Sci Ltd, 2017) Khusayfan, Najla M.; Qasrawi, A. F.; Khanfar, Hazem K.The effect of the Yb, In, Ag and Au thin film metal substrates on the structural and electrical properties of Bi2O3 thin films are investigated by means of X-ray diffraction, impedance spectroscopy an current-voltage characteristic techniques. The Bi2O3 films are observed to exhibit a crystallization nature depending on the crystal structure of the substrate. Particularly, when the metal substrate is facing centered cubic, the Bi2O3 prefers the gamma-phase of body centered cubic crystallization for the (Yb, Ag and Au)/Bi2O3 interfaces. Whereas when a tetragonal substrate (indium) is used, the tetragonal beta-Bi2O3 single phase is preferred. All structural parameters presented by the lattice constant, degree of orientation, dislocation density, micro-strain and grain size are observed to strongly depend on the crystal type. In addition, the evaluation of the Schottky barrier formation at the (Yb, In, Ag, Au)/Bi2O3/Au interfaces by the current-voltage characteristics, revealed that the (In, Au)/Bi2O3/Au interface exhibit ohmic nature of contact and the (Yb,Ag)/Bi2O3/Au are of Schottky type, the rectification ratio for the Yb/Bi2O3/Au interface reaches a value of 10(5) indicating the applicability of these interfaces in CMOS digital logic devices. Moreover, the impedance spectroscopy analysis revealed that the ohmic interfaces exhibit a negative capacitance effect. The In/beta-Bi2O3/Au and Yb/.-Bi2O3/Au interfaces are performing as microwave traps with wave absorption percentage of 62% and 92% at frequencies of 193 and 1200 MHz, respectively. The features of the devices are promising as they indicate the applicability as microwave resonator and fast electronic switches.Article Citation - WoS: 3Citation - Scopus: 3Enhancement of the Performance of the Cu2se Band Filters Via Yb Nanosandwiching(Wiley, 2019) Khusayfan, Najla M.; Qasrawı, Atef Fayez Hasan; Qasrawi, A. F.; Khanfar, Hazem K.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringIn this article, we report the experimental and theoretical modeling on the band pass filters that are made of two thin film layers of Cu2Se coated onto aluminum substrates and nanosandwiched with 50 nm ytterbium layers. The nanosandwiching of Yb between two layers of Cu2Se is found to decrease the lattice constant, the defect density, and the strain and increase the grain size in the Cu2Se. Electrically, it is observed that, Al/Cu2Se/Al structure exhibits wave trap characteristics with notch frequency of 1.31 GHz. The Yb-layers improved the performance of the band pass filters by increasing the amplitude of the reflection coefficients, increasing the return loss values and decreasing the voltage standing wave ratios. The calculated conduction and wave trapping parameters nominate the Yb-nanosandwiched Cu2Se films for use in communication technology as they exhibit negative capacitance effect and narrow band pass range.Article Citation - WoS: 21Citation - Scopus: 21Design and Applications of Yb/Ga2< Schottky Barriers(Ieee-inst Electrical Electronics Engineers inc, 2017) Khanfar, Hazem K.; Qasrawı, Atef Fayez Hasan; Qasrawi, Atef F.; Zakarneh, Yasmeen A.; Gasanly, N. M.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringIn this paper, the Ga2Se3 crystals are used to design a Yb/Ga2Se3/C Schottky barrier. The device structure is investigated by the X-ray diffraction technique, which reveals a monoclinic-face-centered cubic interfacing type of structure. The barrier is studied by means of current (I)-voltage (V) characteristics in the dark and under light through photoexcitation from tungsten lamp and from the He-Ne laser. In addition, the impedance spectroscopy of these devices is studied in the frequency range of 10-1400 MHz. The photoexcited I-V curve analysis allowed investigating the biasing voltage, illumination power, and energy effects on the diode physical parameters, which are presented by the rectification ratio, the Schottky barrier height, the ideality factor, the series resistance, the photosensitivity, the responsivity, and the external quantum efficiency (EQE). While a maximum photosensitivity of 42 was observed for laser excitation with a wavelength of 632 nm at a reverse bias of 4.4 V, the EQE reached value of 1652% at 19.0 V. On the other hand, the ac current conduction analysis of the electrical conductivity, which was determined from the impedance spectral analysis, indicated that the ac signal processing through the Yb/Ga2Se3/C samples is due to the correlated hopping conduction through localized states of Fermi density of 3.98 x 10(19) eV(-1) cm(-3). The high-and biasing-dependent EQE% nominates the Yb/Ga2Se3/C as a tunable optoelectronic device.Article Citation - WoS: 2Citation - Scopus: 2Mgo/Gase0.5< Heterojunction as Photodiodes and Microwave Resonators(Ieee-inst Electrical Electronics Engineers inc, 2016) Qasrawi, Atef F.; Khanfar, Hazem K.; Gasanly, N. M.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.
