6 results
Search Results
Now showing 1 - 6 of 6
Article Citation - WoS: 4Citation - Scopus: 4Characterization of the Ge/Bi2< Interfaces(Univ Fed Sao Carlos, dept Engenharia Materials, 2019) Alharbi, Seham Reef; Qasrawi, Atef FayezIn this article, the properties of the Ge/Bi2O3 interfaces as microwave cavities are reported and discussed. The interface is composed of monoclinic Bi2O3 films grown onto polycrystalline cubic Ge substrate. It is observed that consistent with the theoretical design of the energy band diagram, the experimental current-voltage characteristics of the Yb/Ge/Bi2O3/C hybrid device structure exhibits electronic switching property. In addition, the capacitance, resistance and microwave cutoff frequency spectral analysis in the frequency domain of 0.01-1.50 GHz revealed a frequency dependent tunability of the device. Moreover, while the Yb/Bi2O3/C interface displays negative capacitance effect, the Yb/Ge/Bi2O3/C interfaces are also found to have the ability of altering the resistance up to three orders of magnitude. Such property allowed reaching a cut off frequency up to 116 GHz. The electronic features of the device indicated that the Ge/Bi2O3 interfaces are attractive for production of negative capacitance field effect transistors and band pass/reject filters.Article Citation - WoS: 2Role of Au Nanosheets in Enhancing the Performance of Yb/Zns Tunneling Photosensors(Natl inst R&d Materials Physics, 2020) Abusaa, M.; Qasrawi, A. F.; Assad, B. M.; Khanfar, H. K.In this study, the effects of Au nanosheets of thicknesses of 50 nm on the structural, electrical and photoelectrical properties of Yb/ZnS/CdS/Au (ZAC-0) devices is considered. Stacked layers of ZnS and CdS which are prepared by the thermal evaporation technique onto Yb substrates under vacuum pressure of 10(-5) mbar exhibits rectifying characteristics. For these diodes a reverse to forward current ratios of similar to 10(5) at biasing voltage of 0.60 V is determined. Insertion of Au nanosheets between the stacked layers of ZnS and CdS increased the current values by three orders of magnitude and changed the current conduction mechanism from thermionic emission to tunneling under reverse biasing conditions. The ZAC-0 device, exhibit a barrier height lowering and barrier widening upon insertion of Au nanosheets. After the participation of Au nanosheets in the structure of the ZAC-0 devices, large photosensitivity and responsivity accompanied with high external quantum efficiency is observed. The responsivity to 406 nm laser radiation is biasing voltage dependent and reaches 135 mA/W at 0.60 V. The features of the Yb/ZnS/Au/CdS/Au photosensors nominate them as promising candidates for use in light communication technology as signal receivers.Article Citation - WoS: 10Citation - Scopus: 9Structural and Optoelectronic Properties of Moo3 Interfaces(Wiley-v C H verlag Gmbh, 2019) Alharbi, Seham Reef; Qasrawi, Atef FayezIn this article, the authors discuss the growth nature, the structural, optical and dielectric properties of CuSe thin films deposited onto MoO3 substrate. The films are studied by the X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and ultraviolet-visible light spectroscopy techniques. CuSe thin films are observed to exhibit strained nature of growth when grown onto MoO3 amorphous substrates. Optically, the MoO3/CuSe films are found to exhibit conduction (Delta Ec) and valence (Delta Ev) band offsets of values of 3.70 and 3.42 eV, respectively. In addition, a remarkable increase in the absorbability (R lambda) of MoO3 by 72 times at 3.0 eV is obtained as a result of coating it with CuSe. The Delta Ec, Delta Ev, and R lambda values are significantly high and nominate the MoO3/CuSe interfaces for use in many optoelectronic applications. In addition, the dielectric analysis shows that the MoO3/CuSe heterojunction exhibit optical conductivity parameters that make it suitable for use in optical communications. Particularly, the Drude-Lorentz modeling of the imaginary part of the dielectric constant for the MoO3/CuSe interfaces displays mobility and plasmon frequency values of 7.76 cm(2) V-1 s(-1) and 3.78 GHz, respectively. The obtained plasmon frequency values indicate the applicability of this device in microwave technology.Article Citation - Scopus: 2Role of au nanosheets in enhancing the performance of yb/zns/cds/au tunneling photosensors(S.C. Virtual Company of Phisics S.R.L, 2020) Abusaa,M.; Qasrawi,A.F.; Asaad,B.M.; Khanfar,H.K.In this study, the effects of Au nanosheets of thicknesses of 50 nm on the structural, electrical and photoelectrical properties of Yb/ZnS/CdS/Au (ZAC-0) devices is considered. Stacked layers of ZnS and CdS which are prepared by the thermal evaporation technique onto Yb substrates under vacuum pressure of 10-5 mbar exhibits rectifying characteristics. For these diodes a reverse to forward current ratios of ~105 at biasing voltage of 0.60 V is determined. Insertion of Au nanosheets between the stacked layers of ZnS and CdS increased the current values by three orders of magnitude and changed the current conduction mechanism from thermionic emission to tunneling under reverse biasing conditions. The ZAC-0 device, exhibit a barrier height lowering and barrier widening upon insertion of Au nanosheets. After the participation of Au nanosheets in the structure of the ZAC-0 devices, large photosensitivity and responsivity accompanied with high external quantum efficiency is observed. The responsivity to 406 nm laser radiation is biasing voltage dependent and reaches 135 mA/W at 0.60 V. The features of the Yb/ZnS/Au/CdS/Au photosensors nominate them as promising candidates for use in light communication technology as signal receivers. © 2020, S.C. Virtual Company of Phisics S.R.L. All rights reserved.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: 3Citation - Scopus: 3Structural, Compositional and Optical Properties of Gallium Selenide Thin Films Doped With Cadmium(Wiley-v C H verlag Gmbh, 2008) Qasrawi, A. F.; Saleh, A. A.Polycrystalline cadmium doped gallium selenide thin films were obtained by the thermal co-evaporation of GaSe crystals and Cd grains onto glass substrates. The structural, compositional and optical properties of these films have been investigated by means of X-ray diffraction, energy dispersive X-ray analysis and UV-visible spectroscopy techniques, respectively. Particularly, the elemental analysis, the crystalline nature, the energy band gap, the refractive index, the dispersion energy and static dielectric constant have been identified. The absorption coefficient spectral analysis in the sharp absorption region revealed a direct forbidden energy band gap of 1.22 eV. The cadmium doping has caused a significant decrease in the values of the energy band gap and in all the dispersive optical parameters, as well. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinbeim.
