Yazar "Qasrawi, A. F." seçeneğine göre listele

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    Ag/SeO2/C avalanche type resonant tunneling schottky barriers
    (SciELO - Scientific Electronic Library Online, 2022) Al Garni, Sabah E.; Qasrawi, A. F.; Khusayfana, Najla M.
    Herein, the design and characterization of Ag/SeO2/C avalanche type resonant tunneling devices are reported. Thin pellets of SeO2 nano-powders pressed under hydraulic pressure of 1.0 MPa which is used as the active material are characterized. They showed tetragonal structure refereeing to space group of and lattice parameters of 7.866 ? and 5.336 ? . The current-voltage characteristic curves have shown that SeO2 can perform as active media to produce resonant tunneling diodes when forward biased and as avalanche type diode when reverse biased. The peak to valley current ratios of these diodes reached 18.3. In addition, the impedance spectroscopy measurements have shown that the device works in the low impedance mode when operated in the microwave range of frequency near 1.50 GHz. Negative conductance effect is observed in that frequency domain. The features of the Ag/SeO2/C nominate them for use as signal amplifiers and microwave oscillators.
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    Characterization and applications of ITO/SeO2 interfaces
    (Springer Link, 2022) Alfhaid, Latifah Hamad Khalid; Qasrawi, A. F.
    Herein, indium tin oxide (ITO) thin film substrates are employed to fabricate ITO/SeO2 multifunctional interfaces. The effects of ITO substrates on the physical properties of SeO2 thin films are explored by the structural, morphological, optical and electrical characterization techniques. Amorphous SeO2 thin films are prepared by the thermal evaporation technique under a vacuum, pressure of 10– 5 mbar, that exhibit induced crystallization process when it is coated onto ITO substrates. ITO substrates additionally forced evolution of SeO2 nanotubes of diameters of 10–20 nm. Optically, coating SeO2 onto ITO substrates enhance the light absorbability in the visible and infrared ranges of light, blue shifted the energy band gap of SeO2 and forced dielectric resonance at 3.42 eV and 2.27 eV. Electrically, the ITO/SeO2/Ag devices display negative conductance and negative capacitance effects in the frequency domains of 0.01–0.35 GHz and 0.01–1.80 GHz, respectively. These features are beneficial for signal amplification and noise reduction in electronic circuits. In addition, the impedance spectroscopy analyses shows that the ITO/SeO2/Ag devices operate at high impedance mode in the microwave frequency domain. It also shows band stop filter characteristics that are well performing in the gigahertz frequency domain. The features of the band stop filter nominate the ITO/SeO2/Ag devices for use in 5G technologies.
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    Enhanced structural, optical and electrical properties of polycrystalline WO3 thin films achieved by aluminum nanosheets coating
    (Iop Publishing Ltd, 2024) Qasrawi, A. F.; Khanfar, Hazem K.
    Herein the effects of aluminum nanosheets on the structural, morphological, optical and electrical properties of tungsten oxide thin films are reported. Polycrystalline phase of the thermally evaporated WO3 was achieved by the pulsed laser welding technique. The polycrystalline films are then coated with Al nanosheets of thicknesses of 100 nm and 150 nm by the ion coating technique. It is observed that Al induces the domination of the hexagonal structure of WO3 over the tetragonal. Associated with the enhanced crystallinity the light absorption in the films increased by more than 60% and the energy band gap narrowed significantly. Namely the energy band gap of the as grown WO3 decreased from 3.15 eV to 2.85 eV and 2.59 eV as the Al layer thickness increased from 100 to 150 nm, respectively. It is also observed that crystalline films of WO3 exhibited lower electrical resistivity compared to films fabricated by other techniques. The temperature dependent electrical resistivity measurement was carried out in the temperature range of 310-420 K. It showed room temperature values of 2.5 ( Omega cm), 2.2 ( Omega cm) and 1.9 ( omega cm) and impurity levels centered at 0.25 eV, 0.34 eV and 0.16 eV for uncoated and films coated with Al nanosheets of thicknesses of 100 nm and 150 nm, respectively. The enhanced crystallinity that is accompanied with narrower energy band gap and lower electrical resistivity values make crystalline WO3 films promising for optoelectronic applications.
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    ITO/MgSe interfaces designed as gigahertz/terahertz filters
    (IOP Science, 2023) Almotiri, R. A.; Qasrawi, A. F.
    Herein a new class of MgSe gigahertz/terahertz band filters operatives in the frequency domain of 1.0 GHz-1.86 THz is fabricated and experimentally tested. MgSe band filters are coated onto glass and indium tin oxide (ITO) substrates by the thermal evaporation technique under a vacuum pressure of 10-5 mbar. Thin films of MgSe are structurally, morphologically, compositionally, optically and electrically characterized. It is observed that ITO substrates induce the growth of monophasic of MgSe, enhances the crystallinity of the films and blueshifts the energy band gaps of MgSe. Practical applications were verified by impedance spectroscopy technique through imposing an ac signal of driving frequency in the domain of 10.0 MHz-1.8 GHz between the terminals of ITO/MgSe/Au (IMA) devices. It is observed that the IMA devices exhibit negative capacitance effect. Analysis of the cutoff frequency spectra has shown that IMA devices can reveal wide range of tunability in the gigahertz frequency domain. In addition, the cutoff frequency spectra show values reaching ~1.86 THz for signals of driving frequencies of ~1.0 GHz. Evaluation of the magnitude of the reflection coefficient spectra and return loss spectra for these devices show that the IMA devices can perform as bandstop filters with return loss values exceeding 20 dB at 1.0 GHz. The features of the ITO/MgSe/Au devices are appropriate for the 5G/6G technology needs indicating that the device can be employed in communication technology and other gigahertz/terahertz applications.
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    p-Si/n-CrSe2 Heterojunctions Designed as High-Frequency Capacitors and Photosensors
    (Springer, 2024) Algarni, Sabah E.; Qasrawi, A. F.; Khusayfan, Najla M.; Alharbi, Seham R.; Alfhaid, Latifah Hamad Khalid
    In this work, polycrystalline n-CrSe2 nanosheets with thickness of 100 nm are grown on p-type Si wafers by the thermal deposition technique under vacuum pressure of 10(-5) mbar. Structural and optical investigations showed the preferred growth of the trigonal phase of CrSe2 on Si substrates. Direct allowed transitions within an energy band gap of 2.60 eV were found to be dominant in the films. Silver contacts on the layers allowed construction of hybrid optoelectronic device structure formed from Ag/p-Si Schottky arm and p-Si/n-CrSe(2)pn junction. The device runs in such a way that forward biasing of the Schottky arm is accompanied by a reverse biasing of the pn junction. It is observed that the hybrid device structure can perform as a high-frequency capacitor. The capacitance-voltage characteristic curves show that these capacitors can respond to ac signals with frequencies of 100 MHz. They also exhibit bandstop filter characteristics allowing the passing of signals with return loss and voltage standing wave ratios exceeding 10 dB and 1.76, respectively, at 60 MHz. The device under study displayed rectifying and photo-sensing properties with an asymmetry ratio of 60 in the dark and 217 under excitation of visible light. Visible light excitation of these photosensors displayed voltage biasing dependence in their current responsivity, external quantum efficiency and specific detectivity, reaching values of 0.24 A/W, 65.2% and 4.83 x 10(9) Jones, respectively. The features of the hybrid devices which use CrSe2 nanosheets as active media make them good candidates for use in radio wave and visible light communication technologies.
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    Yb/WO3/Ga2S3/Au multifunctional electronic hybrid devices fabricated as tunneling diodes, MOSFETS, microwave resonators and 5G band pass/reject filters
    (Virtual Co Physics Srl, 2022) Qasrawi, A. F.; Abu Alrub, S. N.
    Herein, Tungsten trioxide-gallium sulfide heterojunctions which are prepared by the thermal evaporation technique under a vacuum pressure of 10(-5) mbar are employed as active media to fabricate a multifunctional device. The WO3/Ga2S3 (WG) heterojunctions which are deposited onto Yb substrates and top contacted with Au pads of areas of 1.5x 10(-2) cm(2) displayed electronic hybrid device structure composed of two Schottky arms connected to a pn junction. The constructed Yb/WG/Au devices showed tunneling diode characteristics with current conduction dominated by thermionic emission and quantum mechanical tunneling. In additions, the capacitance-voltage characteristic curves indicated the formation of PMOS and NMOS under reverse and forwards biasing conditions demonstrating a metal oxide semiconductor fields effect (MOSFET) transistor characteristics. Moreover, the impedance spectroscopy tests on the devices have shown that the device can perform as tunable microwave resonator suitable for 5G technologies. The resonator showed frequency based capacitance tunability and displayed microwave band pass/reject filter characteristics. The microwave cutoff frequency of the Yb/WG/Au band filters reaches 9.65 GHz with voltage standing wave ratios of 1.06 and return loss factor of similar to 29 dB.
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    ZnPc based multifunctional devices designed as fast capacitors, rectifiers, infrared detectors and microwave resonators adequate for 6 G technology applications
    (Iop Publishing Ltd, 2024) Qasrawi, A. F.; Daragme, Rana B.
    Herein Zinc phthalocyanine (ZnPc) based multifunctional devices are fabricated and characterized. The device fabrication included formation of an Au nanosheets onto n-Si wafers and coating these nanosheets with 500 nm thick ZnPc layer. Silver and platinum were used to form a Schottky and an ohmic contacts with n-Si and ZnPc, respectively. The device hybrid structure (Ag/n-Si/Au/p-ZnPc/Pt; abbreviated as ASZ) is composed of Ag/n-Si Schottky arm and p- and n- layers forming pn junction separated by Au nanosheets. Electrical and photoelectrical measurements on the ASZ devices have shown their ability to perform as conventional metal-oxide-semiconductor capacitors (CMOS). These CMOS devices showed light and frequency controlled charge accumulation, depletion and inversion mechanisms within the range of 1.0-50 MHz. The flat band and threshold voltages of the ASZ capacitors are engineered by the imposed ac signal frequency and by infrared (IR) light. In addition, ASZ devices performed as biasing controlled IR photosensors and as current rectifiers. A rectification ratio of 103, IR light sensitivity of 39, specific detectivity of .96 x 10 9 Jones and current responsivity exceeding 9.0 mA W-1 are recorded at biasing voltage of 4.5 V. Moreover ASZ devices displayed microwave resonator characteristics presented by negative capacitance effect, resonance -antiresonance phenomena and high microwave cutoff frequency. The latter is larger than 10 GHz nominating the device for 6 G technology applications.