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Citation - WoS: 11
Citation - Scopus: 12
Effect of Au Nanosandwiching on the Structural, Optical and Dielectric Properties of the as Grown and Annealed Inse Thin Films
(Elsevier Science Bv, 2017) Omareya, Olfat A.; Qasrawi, A. F.; Al Garni, S. E.
In the current work, the structural, optical and dielectric properties of the InSe/Au/InSe nanosandwiched structures are investigated by means of X-ray diffraction and UV-visible light spectrophotometry techniques. The insertion of a 20 and 100 nm thick Au metal slabs between two InSe layers did not alter the amorphous nature of the as grown InSe films but decreased the energy band gap and the free carrier density. It also increased; the absorption ratio and the values of dielectric constant by similar to 3 times. The insertion of 100 nm Au layers as a nanosandwich enhanced the drift mobility (31.3 cm(2)/V s) and plasmon frequency (1.53 GHz) of the InSe films. On the other hand, upon annealing, a metal induced crystallization process is observed for the InSe/Au (100 nm)/InSe sandwiches. Particularly, while the samples sandwiched with a layer of 20 nm thickness hardly revealed hexagonal gamma -In2Se3 when annealed at 300 degrees C, those sandwiched with 100 nm Au slab, displayed well crystalline phase of hexagonal gamma -In2Se3 at annealing temperature of 200 degrees C. The further annealing at 300 degrees C, forced the appearing of the orthorhombic In4Se3 phase. Optically, the annealing of the InSe/Au(100 nm)/InSe at 200 degrees C improved the absorption ratio by similar to 9 times and decreased the energy band gap. The nanosandwiching technique of InSe seems to be promising for the engineering of the optical properties of the InSe photovoltaic material.
Citation - WoS: 6
Citation - Scopus: 6
Design and characterization of (Al, C)/p-Ge/p-BN/C isotype resonant electronic devices
(Wiley-v C H verlag Gmbh, 2015) Al Garni, S. E.; Qasrawi, A. F.
In this work, a Ge/BN isotype electronic device that works as a selective microwave bandstop filter is designed and characterized. The interface is designed using a 50-m thick p-type BN on a 0.2-m thick p-type germanium thin film. The modeling of current-voltage characteristics of the Al/Ge/BN/C channel of the device revealed that the current is dominated by thermionic emission and by the tunneling of charged particles through energy barriers. The evaluation of the conduction parameters reflected a resonant circuit with a peak-to-valley current ratio of (PVCR) of 63 at a peak (V-p) and valley (V-v) voltages of 1.84 and 2.30V, respectively. The ac signal analysis of the Al/Ge/BN/C channel that was carried out in the frequency range of 1.0-3.0GHz displayed a bandstop filter properties with notch frequency (f(n)) of 2.04GHz and quality factor (Q) of 102. The replacement of the Al electrode by C through the C/Ge/BN/C channel caused the disappearance of the PVCR and shifted f(n) and Q to 2.70GHz and 100, respectively. The features of the Ge/BN device are promising as they indicate the applicability of these sensors in communication technology.
Citation - WoS: 9
Citation - Scopus: 8
Exploring the Optical Dynamics in the Ito/As_{2< Interfaces}
(Springer, 2019) Al Garni, S. E.; Qasrawi, A. F.
In this work, the effects of indium tin oxide (ITO) substrates on the structural, compositional, optical dielectric and optical conduction properties of arsenic selenide thin films are investigated. The As2Se3 films which are prepared by the thermal deposition technique under vacuum pressure of 10(-5) mbar exhibit an induced crystallization process, improved stoichiometry, increased optical transmittance in the visible range of light and increased dielectric response in the infrared range of light upon replacement of glass substrates by ITO. The ITO/As2Se3 interfaces exhibit conduction and valence band offset values of 0.46 eV and 0.91 eV, respectively. The experimental optical conductivity spectra are theoretically reproduced with the help of the Drude-Lorentz approach for optical conduction. In accordance with this approach, owing to the improved crystallinity of the arsenic selenide, the deposition of As2Se3 onto ITO substrates increases the drift mobility value from similar to 17.6 cm(2)/Vs to 34.6 cm(2)/Vs. It also reduces the density of free carriers by one order of magnitude. The ITO/As2Se3/C heterojunction devices which are tested as band filters which may operate in the frequency domain of 0.01-3.0 GHz revealed low pass filter characteristics below 0.35 GHz and band pass filter characteristics in the remaining spectral range.
Citation - WoS: 6
Citation - Scopus: 6
Physical Properties of the Bi_1.5zn_{0.92-2x< Solid Solutions}
(Elsevier Sci Ltd, 2016) Al Garni, S. E.; Qasrawi, A. F.; Mergen, A.
The Hf doping effect on the structural, compositional, optical, electrical and dielectric properties of the bismuth-zinc-niobium oxide pyrochlore ceramics is explored by means of scanning electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet-visible light spectroscopy in the wavelength range of 200-1100 nm, temperature dependent electrical resistivity measurements in the range of 300-460 K and dielectric spectroscopy in the frequency range of 0.1-1.0 GHz. The optimum solubility limit in the Bi1.5Zn0.92-2xHfxNb1.5O6.92 solid solution is observed for the Hf content of 0.06. Increasing the Hf content from 0.03 to 0.06 decreased the room temperature, lattice constant, strain, dislocation density, optical energy band gap and electrical resistivity. It also increased the crystallite size and the dielectric constant. The energy band gap of the pure BZN (3.30 eV) decreased to 2.21 and reached 2.10 eV as the Hf content increased from 0.03 to 0.06. This behavior of the BZN suggests its suitability for optical applications of the visible region of light like photovoltaic devices. In addition, the remarkable increase in the dielectric constant from 258 to 280 and 456 nominates the Hf doped pyrochlore for passive mode operation devices like microwave capacitors. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Citation - WoS: 19
Citation - Scopus: 19
Effect of Indium Nano-Sandwiching on the Structural and Optical Performance of Znse Films
(Elsevier Science Bv, 2017) Al Garni, S. E.; Qasrawi, A. F.
In the current study, we attempted to explore the effects of the Indium nanosandwiching on the mechanical and optical properties of the physically evaporated ZnSe thin films by means of X-ray diffractions and ultraviolet spectrophotometry techniques. While the thickness of each layer of ZnSe was fixed at 1.0 mu m, the thickness of the nanosandwiched Indium thin films was varied in the range of 25- 100 nm. It was observed that the as grown ZnSe films exhibits cubic and hexagonal nature of crystallization as those of the ZnSe powders before the film deposition. The cubic phases weighs similar to 70% of the structure. The analysis of this phases revealed that there is a systematic variation process presented by the decreasing of; the lattice constant, compressing strain, stress, stacking faults and dislocation intensity and increasing grain size resulted from increasing the Indium layer thickness in the range of 50-100 nm. In addition, the nanosandwiching of Indium between two layers of ZnSe is observed to enhance the absorbability of the ZnSe. Particularly, at incident photon energy of 2.38 eV the absorbability of the ZnSe films which are sandwiched with 100 nm Indium is increased by 13.8 times. Moreover, increasing the thickness of the Indium layer shrinks the optical energy band gap. These systematic variations in mechanical and optical properties are assigned to the better recrystallization process that is associated with Indium insertion which in turn allows total internal energy redistribution in the ZnSe films through the enlargement of grains. (C) 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license.
Citation - WoS: 14
Citation - Scopus: 15
Investigation of the Physical Properties of the Yb Nanosandwiched Cds Films
(Elsevier Science Sa, 2018) Abed, Tamara Y.; Qasrawi, A. F.; Al Garni, S. E.
In this study, the effects of the sandwiching of a 70 nm thick ytterbium film between two layers of CdS on the structural, compositional, optical and electrical properties are investigated. The X-ray diffraction, scanning electron microscopy, energy dispersion X-ray, visible light spectroscopy and impedance spectroscopy techniques are employed to achieve these effects. It was observed that, the nanosandwiching of Yb between two 500 nm thick films of CdS enhances the crystalline nature of the films without altering the lattice parameters. Particularly, the grain size is increased by 25%, the strain, the defect density and the stacking faults are reduced by 31.5%, 43.7% and 25%, respectively. Optically, the Yb nanosandwiching is observed to enhance the visible light absorbability by at least 2.7 times of the whole range and by 8 times at 1.64 eV. The enhancement of the absorbability is associated with shrinking in the band gap and more interband states. In addition, an increase in the real part of the dielectric constant by 54% is observed when Yb was nanosandwiched in the CdS structure. The modeling of the imaginary part allowed exploring the electron-plasmon interaction parameters. A remarkable increase in the drift mobility from 281 to 996 cm2/Vs associated with plasmon frequency enhancement from 0.84 to 1.38 GHz was determined upon Yb nanosandwiching. The effectiveness of this modeling was verified from the impedance spectra in the frequency domain of 0.01-1.80 GHz, which revealed wave trapping property of ideal values of return loss at notch frequency of 1.35 GHz. Furthermore, the electrical resistivity measurements on the studied samples have shown that the presence of Yb reduced the electrical resistivity and shifts the donor level closer to the conduction band of CdS. The studies nominate the nanosandwiched CdS for use in optical and microwave technologies as dual devices. (C) 2017 Elsevier B.V. All rights reserved.
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.
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 - Scopus: 1
Structural and Electrical Performance of Moo₃ Films Designed as Microwave Resonators
(inst Materials Physics, 2020) Al Garni, S. E.; Qasrawi, A. F.; Alharbi, S. R.; Department of Electrical & Electronics Engineering
In this work, the effect of the insertion of lithium slabs of thicknesses of 50 nm between stacked layers of MoO3 is considered. Stacked layers of MoO3 comprising lithium slabs are prepared by the thermal evaporation technique onto Au substrates under vacuum pressure of 10(-5) mbar. The effects of Li slabs are explored by the X-ray diffraction, scanning electron microscopy, current-voltage characteristics and impedance spectroscopy techniques in the frequency domain of 0.01-1.80 GHz. While the presence of Li slabs did not alter the amorphous nature of structure, it forced the growth of rod-like grains of diameters of 100-160 nm and lengths of 1.5 mu m. Electrically, the presence of Li in the samples enhanced the rectifying properties of the devices and force reverse to forward current ratios larger than 60 times. Li slabs also controlled the negative capacitance effect and resonance -antiresonance regions in the Au/MoO3/MoO3/C stacked layers. While the Au/MoO3/MoO3/C devices displayed high conductance and low impedance values in the studied frequency domain, the Au/MoO3/Li/MOO3/C devices exhibited low conductance and high impedance mode in the frequency domain of 0.01-0.59 GHz. It is also found that the presence of Li slabs improved the performance of the devices through driving it to exhibit lower reflection coefficient and high return loss values near 0.80 GHz. The features of the devices nominate them for use as RF-Microwave traps or resonators.
Citation - WoS: 10
Citation - Scopus: 10
Fabrication and Characterization of Yb/Moo_{3< Devices}
(Elsevier Science Bv, 2019) Al Garni, S. E.; Qasrawi, A. F.
In this study we have explored some of the properties of Yb/MoO3/(C, Yb) thin films as a multifunctional optoelectronic device. While the MoO3 films which are deposited onto glass substrate are found to be of amorphous nature, the Yb metal induced the growth of orthorhombic phase of MoO3. The films are high transparent and exhibit energy band gap value of 3.0 eV which make it sensitive to light signals in the near ultraviolet range of light. In addition, the frequency dependent capacitance-voltage characteristics of Yb/MoO3/(C,Yb) structure display pronounced accumulation, depletion and inversion regions that nominate it for use as tunable metal-oxide-semiconductor MOS device. The physical parameters including the built in voltage, barrier height, flat band and threshold voltages of the MOS capacitors are also determined. Furthermore, the current-voltage characteristics displayed high rectification ratio that could reach 1.26 x 10(4) at biasing voltage of 0.5 V nominating the Yb/MoO3/C device for use as electronic switches. On the other hand, the impedance spectroscopy analysis in the frequency domain of 0.01-1.80 GHz, have shown that the Yb/MoO3/Yb structures are more appropriate for microwave applications than Yb/MoO3/C device. The microwave cutoff frequency for the Yb sandwiched MoO3 exceeds 140 GHz. The return loss for the Yb/MoO3/Yb reaches 26 dB at 1.8 GHz. These values are attractive as they suit microwave low/high pass band fillers.
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.
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.

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