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Article Citation - WoS: 6Citation - Scopus: 6Dielectric Dispersion at the Mn/Znpc Interfaces(Wiley-v C H verlag Gmbh, 2020) Qasrawi, Atef F.; Zyoud, Hadeel M.Herein, the effects of manganese transparent (150 nm) substrates on the structural, nonlinear optical, and dielectric properties of zinc phthalocyanine are explored. ZnPc thin films are observed to exhibit deformed crystal structure associated with remarkable enhancement in the light absorbability by 21 times at 2.62 eV and by 173 times in the near-infrared (NIR) region of light upon replacement of glass by transparent Mn substrates. The Mn layer also causes a redshift in the energy bandgap, allows generation of free carrier absorption process and increases the dielectric constant by more than 169% in the NIR region. The interaction between the manganese substrates with the organic ZnPc thin layers decreases the free holes density, widens the plasmon frequency range, and improves the drift mobility of holes. The nonlinear dielectric response with the highly improved light absorbability in the NIR range of light nominates the Mn/ZnPc thin films for optoelectronic applications.Article Citation - WoS: 7Citation - Scopus: 7Structural and Dielectric Properties of Ba1-x< Solid Solutions(Wiley-v C H verlag Gmbh, 2021) Qasrawi, A. F.; Sahin, Ethem Ilhan; Abed, Tamara Y.; Emek, MehribanHerein, lanthanum doping effects on the structural, dielectric, and electrical properties of Ba1-xLax(Zn1/3Nb2/3)O-3 (BZN) solid solutions are focused upon. The La contents which are varied in the range of 0.02-0.20 exhibit a solubility limit of x = 0.02. Although minor phases of Ba5Nb4O15 and Ba3LaNb3O12 appear for samples doped with La contents of x = 0.05 and x = 0.10, they play no remarkable role for the enhanced structural and dielectric properties of BZN. The La doping content of x = 0.02 succeeds in increasing the crystallite size by 51.16% and lowering the microstrain by 34.18% and defect concentration by 63.10%. La-doped BZN ceramics display higher values of relative density and electrical conductivity. The analyses of the dielectric spectra as a function of temperature display dielectric relaxation behavior above 120 degrees C. In the temperature range of 20-120 degrees C, La doping changes the temperature coefficient of dielectric constants from +30 ppm degrees C-1 in pure samples to -341 ppm degrees C-1 in samples doped with La contents of x = 0.10. The enhancements in structural parameters, density values, and dielectric responses that are achieved via La doping make BZN ceramics more suitable for electronic device fabrication.Article Citation - WoS: 4Citation - Scopus: 4Optical Dynamics at the Au/Znpc Interfaces(Univ Fed Sao Carlos, dept Engenharia Materials, 2020) Qasrawi, A. F.; Zyoud, Hadeel M.In this work, the optical dynamics and the structural properties of the zinc phthalocyanine which are coated onto 150 nm thick Au substrates are studied by the X-ray diffraction and optical spectrophotometry techniques. The Au/ZnPc interfaces appears to be strongly affected by the large lattice mismatches at the interface. It is observed that the coating ZnPc onto Au substrates increases the light absorbability by 4.7 and 128.2 times in the visible and infrared regions of light, respectively. Au substrates activated the free carrier absorption mechanism in the ZnPc thin films in the infrared range of light. In addition, the transparent Au substrates forced narrowing the energy band gap in both of the Q and B bands. It also increased the dielectric constant value by similar to 3.5 times in the IR range. The enhancements in the optical properties of ZnPc that resulted from the thin Au substrates make the ZnPc more suitable for optoelectronic, nonlinear optical applications and for electromagnetic energy storage in the infrared range of light.Article Citation - WoS: 10Citation - Scopus: 9Tunable Au/Ga2< 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 EngineeringIn 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.Article Citation - WoS: 5Citation - Scopus: 5Formation and Negative Capacitance Effect in Au/Bi2< Heterojunctions Designed as Microwave Resonators(Natl inst R&d Materials Physics, 2018) Al Garni, S. E.; Qasrawi, A. F.; Department of Electrical & Electronics EngineeringIn 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.
