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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14411/18
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Article Citation - WoS: 2Citation - Scopus: 1Characterization of Pbmo<sub>0.3</Sub>w<sub>0.7< Crystal: a Potential Material for Photocatalysis and Optoelectronic Applications(Wiley-v C H verlag Gmbh, 2024) Isik, Mehmet; Gasanly, Nizami MamedPbMo0.3W0.7O4 semiconductor crystal, which contains the balanced ratios of Mo and W, is grown for the first time by Czochralski method. The structural and optical properties of the crystal are investigated in detail in the present study. Structural analysis shows that crystal has tetragonal structure like PbMoO4 and PbWO4 compounds. The optical characteristics are studied by transmission, Raman, FTIR and photoluminescence methods. The bandgap energy is found to be 3.18 eV, and the positions of the conduction and valence bands are determined. The vibrational characteristics are studied by means of Raman and FTIR spectroscopy techniques. Photoluminescence spectrum presents three peaks around 486, 529, and 544 nm which fall into the green emission spectral range. Taking into account the properties of the compound, it is stated that PbMo0.3W0.7O4 (or Pb(MoO4)(0.3)(WO4)(0.7)) has the potential to be used in water splitting applications and optoelectronic devices that emit green light.Article Citation - WoS: 11Cd-Doping Effects on the Properties of Polycrystalline Α-in<sub>2</Sub>se<sub>3< Thin Films(Wiley-v C H verlag Gmbh, 2002) Qasrawi, AFThe X-ray diffraction has revealed that the polycrystalline hexagonal structured alpha-In2Se3 thin films grown at substrate temperature of 200degreesC with the unit cell parameters a=4.03degreesA and c=19.23degreesA becomes polycrystalline hexagonal structured InSe with a unit cell parameters of a=4.00degreesA and c=16.63degreesA by Cd-doping. The analysis of the conductivity temperature dependence in the range 300-40 K revealed that the thermionic emission of charged carriers and the variable range hopping are the predominant conduction mechanism above and below 100 K, respectively. Hall measurements revealed that the mobility is limited by the scattering of charged carriers through the grain boundaries above 200 K and 120 K for the undoped and Cd-doped samples, respectively. The photocurrent (I-ph) increases with increasing illumination intensity (T) and decreasing temperature up to a maximum temperature of similar to100 K, below which I-ph is temperature invariant. It is found to have the monomolecular and bimolccular recombination characters at low and high illumination intensities, respectively. The Cd-doping increases the density of trapping states that changes the position of the dark Fermi level leading to the deviation from linearity in the dependence of I-ph on F at low illumination intensities.Article Citation - WoS: 1Citation - Scopus: 1Pseudodielectric Dispersion in As<sub>2</Sub>se<sub>3< Thin Films(Wiley-v C H verlag Gmbh, 2020) Kayed, Tarek S.; Kayed, Tarek Said; Qasrawi, Atef F.; Qasrawı, Atef Fayez Hasan; Kayed, Tarek Said; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringHerein, X-ray diffraction, energy dispersive X-ray spectroscopy, and spectral ellipsometry techniques are used to investigate the structural, pseudo-optical, and pseudodielectric properties of arsenic selenide thin films. The stoichiometric films which are prepared by the thermal evaporation technique are found to prefer the amorphous nature of growth. While the pseudoabsorption coefficient spectra display strong absorption bands at 1.84, 1.81, 1.41, and 1.13 eV, the preferred pseudo-optical transitions happen within a direct forbidden energy bandgap of 1.80 eV. In addition, the real part of the pseudodielectric spectra displays three strong resonance peaks at critical energy values of 2.33, 1.90, and 1.29 eV. Modeling of the imaginary part of the pseudodielectric constant spectra in accordance with the Drude-Lorentz approach results in the existence of six linear oscillators. The response of arsenic selenide to elliptically polarized light signals shows that the films exhibit drift mobility, free electron concentration, and plasmon frequency values in the ranges of 0.21-43.96 cm(2) V(-1)s(-1), 1.90-58.0 x 10(19) cm(-3), and 5.8-32.0 GHz, respectively. The optical conductivity parameters for As2Se3 film nominate it as a promising candidate for the fabrication of tunneling diodes suitable for microwaves filtering up to 32.0 GHz and as thin-film transistors.Article Citation - WoS: 6Citation - Scopus: 5Characterization of Au/As<sub>2< Multifunctional Tunneling Devices(Wiley-v C H verlag Gmbh, 2020) Qasrawi, Atef FayezHerein, the physical design and characterization of the Au/As2Se3 Schottky barrier that is prepared under a vacuum pressure of 10(-5) mbar are reported. The Schottky diodes are characterized by means of X-ray diffraction, energy-dispersive X-ray spectroscopy, current-voltage characteristics, and conductivity, capacitance, and impedance spectroscopy. It is observed that the Schottky barriers exhibit a biasing-dependent large rectification ratio with current conduction mechanisms dominated by the electric field-assisted quantum mechanical tunneling through a barrier height of 0.29 eV and depletion width of 13.3 nm. While the spectral analysis of the alternating current (AC) conductivity reveals mixed conduction with the contribution of both of the tunneling and correlated barriers hopping mechanisms, the capacitance spectra display resonance-antiresonance phenomena at 0.201 GHz. A wide range (0.21-1.80 GHz) of negative capacitance (NC) effects is observed in devices. In addition, the impedance spectroscopy analyses show that the Au/As2Se3 devices exhibit band-stop features with a notch frequency of 1.14 GHz and return loss value of 16 dB. The NC effect, resonance-antiresonance, filtering features, as well as the high rectification ratio at a relatively low biasing voltage (approximate to 0.30 V) nominate the Au/As2Se3 devices for applications which require noise reduction, parasitic effect cancellations, and microwave filtering.Article Citation - WoS: 7Citation - Scopus: 7Enhancements of Light Absorbability, Optical Conductivity, and Terahertz Cutoff Frequency in Stacked Layers of Selenium Via Ag Nanoslabs Sandwiching(Wiley-v C H verlag Gmbh, 2019) Qasrawi, Atef F.; Abu Al Rob, Osama H.Herein, the effects of insertion of Ag layer of thickness of 100 nm between two stacked layers of selenium are investigated by means of X-ray diffraction, scanning electron microscopy, and optical spectrophotometry techniques. While the structural analysis shows the amorphous nature of growth of the stacked layers of Se, the morphology analysis shows the formation of nanorods and nanowires that exhibit lengths and diameters in the ranges of 1.5-2.5 mu m and 36-146 nm, respectively. The optical spectroscopy analysis shows that the presence of Ag between stacked layers of selenium enhances the light absorbability, increases the optical conductivity, and widens the range of the terahertz cutoff frequency. In addition, Ag layers increase the drift mobility from 15.07 to 35.64 cm(2) Vs(-1) and extend the plasmon frequency domain of stacked layers of selenium from 0.45-5.60 to 0.62-5.90 GHz. The calculated optical conductivity parameters and the spectral analysis of the terahertz cutoff frequency that vary in the range of 0.35-13.20 THz indicate the applicability of the Ag sandwiched selenium stacked layers as terahertz cavities suitable for visible-light communications as band-pass filters.Article Citation - WoS: 6Citation - Scopus: 6Fabrication of (au, Mn)/Znpc Interfaces as Radiowave/Microwave Band Filters(Wiley-v C H verlag Gmbh, 2020) Qasrawi, Atef Fayez; Zyoud, Hadeel MohammadHerein, zinc phthalocyanine (ZnPc) layers are used as an active material to fabricated radiowave/microwave band filters. The thin layers of ZnPc are coated onto Au and Mn thin-film substrates to form ohmic and Schottky interfaces, respectively. The Au/ZnPc and Mn/ZnPc devices are structurally and electrically characterized by means of X-ray diffraction and impedance spectroscopy techniques in the frequency domain of 0.01-1.80 GHz, respectively. The structural investigations show that both interfaces exhibit strained structures of the monoclinic phase of ZnPc. It is also observed that while the Au/ZnPc/Ag devices display negative capacitance (NC) effects in the microwave region above 1.46 GHz, the Mn/ZnPc/Ag devices show resonance-antiresonance capacitive response in the radiowave region accompanied with NC effects in the range of 0.06-1.80 GHz. In addition, analyses of the reflection coefficient spectra have shown the ability of the (Mn, Au)/ZnPc/Ag interfaces to behave as a typical high-/low-bandpass filters. The filters can be operated in microwaves and radiowave ranges. The return loss spectral investigations on these filters have shown their ability to reach the market standards.Article Citation - WoS: 12Citation - Scopus: 12Band Offsets, Optical Conduction, and Microwave Band Filtering Characteristics of Γ-in<sub>2</Sub>se<sub>3< Heterojunctions(Wiley-v C H verlag Gmbh, 2020) Qasrawi, Atef F.; Kmail, Reham R.Herein, the design and experimental characterization of gamma-In2Se3/CuO interfaces are considered. Thin films of gamma-In(2)Se(3)are coated with thin layers of CuO at room temperature. The heterojunction device is structurally, morphologically, and optically characterized. It is observed that the coating of CuO onto gamma-In(2)Se(3)engenders the formation of CuSe(2)at the ultrathin interface. The gamma-In2Se3/CuO heterojunctions exhibit maximum possible conduction and valence band offsets of values 0.47 and 0.96 eV, respectively. The dielectric spectra display two dielectric resonance peaks at 2.96 and 1.78 eV. In addition, analyses of the optical conductivity spectra reveal accurate drift mobility and plasmon frequency values of 31.31 cm(2) Vs(-1)and 1.5 GHz, respectively. The ability of the device to control the signal propagation at gigahertz level is experimentally tested by the impedance spectroscopy technique which proved the ability of the device to behave as bandpass filters of notch frequency of 1.49 GHz. The gamma-In2Se3/CuO heterojunction devices are also observed to display terahertz cutoff frequency values of approximate to 24 THz in the infrared (IR) range of incident photon energy and approximate to 193 THz in the ultraviolet light range. The nonlinear optical performance of the device nominates it for use as terahertz/gigahertz band filters.Article Citation - WoS: 7Citation - Scopus: 7Structural and Dielectric Properties of Ba<sub>1-<i>x</I>< 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: 3Citation - Scopus: 3Enhancement of Nonlinear Optical and Dielectric Properties of Cu<sub>2</Sub>o Films Sandwiched With Indium Slabs(Wiley-v C H verlag Gmbh, 2020) Omar, Ahmad; Qasrawi, Atef F.In this work, the effects of the insertion of indium slabs of thickness 100 nm on the performance of stacked layers of Cu2O are reported. Cu2O/In/Cu2O thin films coated onto ultrasonically cleaned glass substrates are structurally, morphologically, optically, and dielectrically studied. The glassy films of Cu2O display larger, well-ordered grains in an amorphous sea of Cu2O upon insertion of indium slabs between layers of Cu2O. Optically, the indium slabs increase the light absorbability in the IR region by 12.5 times, narrow the energy bandgap, and widen the energy band tails region. They also enhance the nonlinearity in the dielectric response and increase the dielectric constant values by 2.5 times. In addition, the optical conductivity parameters are obtained from the fittings of the dielectric spectra. The analyses reveal an enhancement in the drift mobility, plasmon frequency, and free carrier density via stacking of the indium layer between layers of Cu2O. The drift mobility and plasmon frequency values reach 232.4 cm(2) V-1 s(-1) and 3.95 GHz at a reduced hole-plasmon frequency value of 6.0 x 10(14) Hz (2.48 eV). The values are promising as they indicate the applicability of Cu2O/In/Cu2O interfaces in optoelectronics as thin film transistors and electromagnetic wave cavities.Article Citation - WoS: 14Citation - Scopus: 14Ruthenium Nanoparticles Supported on Reduced Graphene Oxide: Efficient Catalyst for the Catalytic Reduction of Cr(vi) in the Presence of Amine-Boranes(Wiley-v C H verlag Gmbh, 2020) Yurderi, Mehmet; Bulut, Ahmet; Kanberoglu, Gulsah Saydan; Kaya, Murat; Kanbur, Yasin; Zahmakiran, MehmetHexavalent chromium (Cr(VI)) is a toxic, mutagen and carcinogen contaminant exist in surface and groundwater, while its reduced form trivalent chromium (Cr(III)) is known as an essential element to normal carbohydrate, lipid and protein metabolism in nature. Addressed herein, for the first time, ruthenium nanoparticles supported on reduced graphene oxide (Ru@rGO) catalyze the reduction of aqueous Cr(VI) to Cr(III) in the presence of amine-boranes; ammonia-borane (AB; NH3BH3), methylamine-borane (MeAB; CH3NH2BH3), dimethylamine-borane (DMAB; (CH3)(2)NHBH3) as reducing agents under mild conditions (at room temperature and under air). Ru@rGO catalyst was reproducibly fabricated through a double-solvent method followed by wet-chemical reduction and characterized by using various spectroscopic and visualization techniques, which showed that the formation of well-dispersed and highly crystalline ruthenium(0) nanoparticles with a mean particle size of 2.7 +/- 0.9 nm on the surface of rGO. The catalytic performance of Ru@rGO was investigated in terms of activity and stability in the ammonia-borane assisted reduction of Cr(VI) to Cr(III), and the sum of the results gained from these catalytic tests revealed that Ru@rGO acts as both active (TOF=7.6 mol Cr2O72-/mol Ru.min) and stable (80% of its initial activity at 90% conversion at 5(th)reuse) heterogeneous catalyst in this significant catalytic transformation. This study also reports kinetic studies for Ru@rGO catalyzed Cr(VI) reduction in the presence of ammonia-borane depending on ruthenium ([Ru]), ammonia-borane ([AB]) concentrations and temperature to shed some light on the nature of the catalytic reaction and activation parameters.