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Citation - WoS: 3
EFFECT OF Y, Au AND YAu NANOSANDWICHING ON THE STRUCTURAL, OPTICAL AND DIELECTRIC PROPERTIES OF ZnSe THIN FILMS
(Natl inst R&d Materials Physics, 2019) Qasrawi, A. F.; Taleb, M. F.
In this article, we report the effects of insertion of yttrium, gold and yttrium-gold (YAu) metallic nano-slabs on the structural, optical and dielectric properties of ZnSe thin films. The ZnSe thin films which are prepared by the thermal evaporation technique under vacuum pressure of 10-5 mbar exhibit hexagonal structure. While the insertion of the 70 nm thick Y layers does not alter the lattice parameters and stress values, the Au and YAu layers increased the lattice parameters along the a- and c-axes and decreased the stress values. In addition, the insertion of these metallic layers slightly alters the value of the energy band gap and increases the width of the interbands. The light absorbability are increased by 1.4, 2.0 and 2.4 times upon insertion of Y, Au and YAu, slabs, respectively. On the other hand, the dielectric and optical conductivity analyses has shown that the use of the YAu stacked metal layers increases the real part of the dielectric constant, the optical conductivity, the drift mobility and extended the plasmon frequency range from 35.1 to 254.0 (Omega cm)(-1), from 1098 to 1766 cm(2)/vs and from 0.94-3.11 GHz to 2.13-4.83 GHz, respectively. The insertion of the two stacked metallic layers between two layers of ZnSe makes the ZnSe more appropriated for thin film transistor technology.
Citation - WoS: 2
Citation - Scopus: 2
Effect of Insertion of Aluminum Nanosheets on the Structural, Optical and Dielectric Properties of Stacked Layers of Selenium
(Natl inst R&d Materials Physics, 2019) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Abu Al Rob, O. H.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
In this work, the time dependent metal induced crystallization process in stacked layers of selenium that are sandwiched with aluminum nanosheets of thicknesses of 50 nm are investigated by means of X-ray diffraction and optical spectrophotometry techniques. The Al nanosheets motivated the growth of orthorhombic phases of selenium and lowered the energy bang gap of the amorphous films from 2.26 to 1.82 eV when the orthorhombic phase is achieved. The time dependent monitoring of the structural and optical properties over eighteen months have shown that both of the orthorhombic and amorphous phases exhibit a second transformation to hexagonal and stabilize at that phase within ten days of the growth time. The presence of the aluminum nanosheets enhanced the light absorbability by 15 and 5 times in the orthorhombic and hexagonal phases, respectively. In addition, the dielectric spectra of the studied films display similar characteristics in the hexagonal phase with slight differences that results from Al nanosheets. The dielectric spectra for both of the amorphous and orthorhombic phases displayed resonance peaks in the visible and infrared ranges of light. The structural and optical analysis that are carried out through this study represent a guide for using the selenium films in optoelectronic technology.
Citation - WoS: 2
Role 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.
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.
Citation - WoS: 10
Citation - Scopus: 9
Tunable Au/Ga_{2< Varactor Diodes Designed for High Frequency Applications}
(Natl inst R&d Materials Physics, 2017) Al Garni, S. E.; Qasrawi, A. F.; Department of Electrical & Electronics Engineering
In this work, the design and characterization of Au/Ga2S3/Yb Schottky barrier is investigated by means of transmittance electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), capacitance spectroscopy, capacitance (C)-voltage (V) characteristics and impedance spectroscopy techniques. The design of the energy band diagram of the amorphous Au/Ga2S3 interface revealed a theoretical energy barrier height (q phi(b)) and built in voltage (qV(bi)) of 2.04 and 1.88 eV, respectively. Experimentally, the qV(bi) was observed to be sensitive to the applied signal frequency. In addition, the capacitance spectra which were studied in the range of 10-1800 MHz, revealed resonance and antiresonance biasing dependent signal oscillations associated with negative capacitance values. On the other hand, impedance spectroscopy analysis revealed band pass/reject filtering properties in all the studied frequency range. The device exhibited a return loss, voltage standing wave ratio and power efficiency of 16.7 dB, 1.3 and 98.3% at 1400 MHz, respectively.
Citation - WoS: 5
Citation - Scopus: 5
Formation and Negative Capacitance Effect in Au/Bi_{2< Heterojunctions Designed as Microwave Resonators}
(Natl inst R&d Materials Physics, 2018) Al Garni, S. E.; Qasrawi, A. F.; Department of Electrical & Electronics Engineering
In this article, the physical design, energy band diagram, temperature dependent electrical resistivity and the impedance spectroscopy measurements of the Au/Bi2O3/ZnS/Ag isotype heterojunction devices are reported. The devices are prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar. Structural, compositional and morphological studies has shown the presence of an expansion in the lattice of Bi2O3 associated with increased strain and dislocation density and decreased grain size as a result of ZnS interfacing. The design of the band diagram indicated that the formed heterojunction exhibit large valence and conduction band offsets that forces charge accumulation at the interface. The Au/Bi2O3/ZnS/Ag device displays negative capacitance (NC) effect in the frequency domain of 0.01-1.50 GHz. The NC effect is interrupted by a resonance-antiresonance phenomenon in the frequency domain of 0.90-1.07 GHz. In addition to the NC effects, the device under study exhibited reflection coefficient and return loss spectra that nominate it for use as microwave cavities or as low pass band filters.

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