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Citation - WoS: 7
Citation - Scopus: 6
Temperature-Dependent Structural Transition, Electronic Properties and Impedance Spectroscopy Analysis of Tl₂ingas_{4< Crystals Grown by the Bridgman Method}
(Elsevier Sci Ltd, 2018) Qasrawi, A. F.; Alkarem, Qotaibah A.; Gasanly, N. M.
In this work, we report the temporary structural modifications associated with the in situ heating of the Tl2InGaS4 crystals in the temperature range of 300-420 K. The analysis of the X-ray diffraction patterns revealed the temperature-independent possible phase transformations between the monoclinic and triclinic phases. The temperature analysis of the lattice parameters, crystallite size, strain, dislocation density and stacking faults has shown a temporary enhancement in the crystallinity of this compound above 375 K. Significant increase in the grain size accompanied to decrease in the strain, defect density and stacking faults was observed above this temperature. The scanning electron microscopy imaging has shown that the crystals are layer structured with high quality layers of thicknesses of similar to 12 nm. In addition the energy dispersive X-ray analysis has shown that the crystal comprise no detectable impurity. Moreover, the room temperature optical characterizations has shown that the Tl2InGaS4 exhibit an energy band gap of 2.5 eV. The temperature dependent electrical resistivity measurements indicated highly resistive crystal with activation energy values of 0.84 and 0.19 eV above and below 375 K, respectively. On the other hand, room temperature impedance spectroscopy analysis in the frequency domain of 10-1800 MHz has shown that the crystal exhibits negative resistance and negative capacitance effects below and above 1580 MHz. The crystals are observed also to behave as band stop filter with notch frequency of 1711 MHz.
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: 7
Citation - Scopus: 7
Enhancing the Optoelectronic Performance of As₂se_{3< Thin Films Via Ag Slabs Sandwiching}
(Elsevier Gmbh, 2020) Qasrawi, A. F.; Alharbi, Seham Reef
In this work, the effects of insertion of Ag slabs of thicknesses of 50, 100 and 200 nm between layers of arsenic selenide are reported. The glassy structured As2Se3 is characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, ultraviolet-visible light spectrophotometry and impedance spectroscopy techniques. While the two stacked layers of As2Se3 exhibited high absorption and energy band gap values that nominate them for optoelectronic applications, the Ag slabs enhanced the light absorbability by 3.98, 5.77, 6.13 times and shrunk the energy band gap by 1.16 %, 7.40 % and 13.8 % for Ag slabs of thicknesses of 50, 100 and 200 nm, respectively. In addition, even though the As2Se3/As2Se3 layers exhibited negative capacitance effect in the frequency domain of 0.01-1.80 GHz, the insertion of Ag slabs removed the negative capacitance effect and forced the capacitance spectra to exhibit resonance at critical frequency of value of 0.23 GHz. The modeling of the capacitance spectra have shown that the geometrical capacitance is increased by one order of magnitude upon Ag slabs insertion. The dynamic capacitance is limited by electrons (holes) plasmonic interaction at the interface between the As2Se3/Ag/As2Se3 layers. Furthermore, the capacitance- voltage characteristics of the As2Se3/Ag/As2Se3 films confirmed the suitability of the devices to exhibit MOS device features. The characteristics of the stacked layers of As2Se3 indicate their multi-functionality as an optical absorbers/receivers and as microwave cavities.
Citation - WoS: 3
Citation - Scopus: 3
Ytterbium Induced Structural Phase Transitions and Their Effects on the Optical and Electrical Properties of Znpc Thin Films
(Springer, 2020) Qasrawi, A. F.; Zyoud, Hadeel M.
In this work, the effects of ytterbium substrates of thicknesses of 150 (Yb-150) and 1000 nm (Yb-1000) on the structural, optical and electrical properties of zinc phthalocyanine (ZnPc) are investigated. While the Yb-150/ZnPc exhibited strained monoclinic structure, the Yb-1000/ZnPc thin films are observed to exhibit phase transitions from monoclinic to triclinic structure. Analysis which targeted observatories of the effects of the Yb-150 substrate on the optical properties indicated that the transparent Yb-150 substrate enhanced the light absorbability by more than 11 times at 1.27 eV. On the other hand, the impedance spectroscopy measurements on the nontransparent Yb-1000/ZnPc/Ag sandwiched structures have shown that these devices could exhibit negative capacitance (NC) effect in the frequency domain of 0.244-1.800 GHz. The NC effect is associated with resonance-anti-resonance response at 0.235 and 0.244 GHz, respectively. The structural, optical and electrical properties of the Yb/ZnPc interfaces indicate its applicability as optoelectronic and/or radio/microwave components.
Citation - WoS: 27
Citation - Scopus: 30
Effects of Au Nanoslabs on the Performance of Cdo Thin Films Designed for Optoelectronic Applications
(Elsevier, 2021) Alharbi, Seham Reef; Qasrawi, A. F.
In this work, the effect of 50 nm thick gold nanosheets on the structural, morphological, optical and electrical properties of stacked layers of CdO are investigated. The insertion of Au nanoslabs decreased the lattice parameters of the cubic unit cells of CdO. It also decreased the microstrain, the defect density, the stacking fault percentage and increased the crystallite and grain sizes. Optically, the light absorbability is enhanced, the energy band gap is shrunk and the optical conductivity is increased. The optical conductivity parameters presented by scattering time, plasmon frequency, drift mobility and free carrier density are all engineered via participation of Au nanosheets. On the other hand, electrical measurements in the frequency domain of 0.01-1.80 GHz indicated that the Au nanosheets forced the capacitance spectra to exhibit negative values and increased the electrical conductivity in the studied frequency domain. The terahertz cutoff frequency is tuned in the range of 5.0-22.0 THz indicating the applicability of the CdO/Au/CdO (CAC) films as terahertz filters. The direct current electrical conductivity measurements have shown that while the CC samples exhibit nondegenerate extrinsic nature of conduction, the CAC samples displayed degenerate/nondegenerate transitions at 400 K. With the feature of negative capacitance that can be used for noise reduction and parasitic capacitance cancellation, the CAC films can be regarded as promising structure for multifunctional device applications.
Citation - WoS: 10
Citation - Scopus: 10
Effects of Indium Slabs on the Structural and Electrical Properties of Stacked Layers of Cu₂o
(Natl inst R&d Materials Physics, 2020) Qasrawi, A. F.; Omar, A.; Department of Electrical & Electronics Engineering
In this work, the structural and electrical properties of stacked layers of Cu2O that comprises indium slabs in its structure are reported. The stacked layers which are coated onto glass and Au substrates under vacuum pressure of 10(-5) mbar are characterized by the X-ray diffraction and impedance spectrometry techniques. While the Cu2O/Cu2O (CC) layers exhibited amorphous nature of growth, those which contained indium slabs (CIC) displayed weak crystallinity The insertion of indium slabs between stacked layers of cuprous oxide highly increased the electrical resistivity and shifted the acceptor level closer to the valance band edge. In addition, the analyses of the conductance and capacitance spectra in the frequency domain of 0.01-1.0 GHz have shown that these two physical parameters are strongly affected by the insertion of indium slabs and by surface deformation effects. The capacitance spectra showed negative capacitance effect (NC) in all the studied frequency domain The NC effects become less pronounced in the CIC samples owing to the changes in the polarization mechanism. The feature of NC effects make both of the CC and CIC samples more appropriate for electronic and telecommunication technology as it can be used in amplifiers to enhance he gain, as parasitic cancellers and as noise reducers.

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