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Article Citation - WoS: 7Citation - Scopus: 7Design of the Zns/Ge pn Interfaces as Plasmonic, Photovoltaic and Microwave Band Stop Filters(Elsevier Science Bv, 2017) Alharbi, S. R.; Qasrawi, A. F.In the current work, we report and discuss the features of the design of a ZnS (300 nm)/Ge (300 nm)/GaSe (300 nm) thin film device. The device is characterized by the X-ray diffraction, electron microscopy, energy dispersive X-ray spectroscopy (EDS), optical spectroscopy, microwave power spectroscopy and light power dependent photoconductivity. While the X-ray diffraction technique revealed a polycrystalline ZnS coated with two amorphous layers of Ge and GaSe, the hot probe tests revealed the formation of pn interface. The optical spectra which were employed to reveal the conduction and valence band offsets at the ZnS/Ge and Ge/GaSe interface indicated information about the dielectric dispersion at the interface. The dielectric spectra of the ZnS/Ge/GaSe heterojunction which was modeled assuming the domination of surface plasmon interactions through the films revealed a pronounced increase in the drift mobility of free carriers in the three layers compared to the single and double layers. In the scope of the fitting parameters, a wave trap that exhibit filtering properties at notch frequency of 2.30 GHz was designed and tested. The ac signals power spectrum absorption reached similar to 99%. In addition, the photocurrent analysis on the ZnS/Ge/GaSe interface has shown it is suitability for photovoltaic and photosensing applications. (C) 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND licenseArticle Citation - WoS: 8Citation - Scopus: 10Structural, Electrical and Dielectric Properties of Bi1.5zn0.92< Pyrochlore Ceramics(Elsevier Sci Ltd, 2012) Qasrawi, A. F.; Mergen, A.The micro-structural, compositional, temperature dependent dielectric and electrical properties of the Bi1.5Zn0.92Nb1.5-xTaxO6.92 solid solution has been investigated. The increasing Ta content from 0.2 to 1.5 caused; single phase formation, a pronounced grain size reduction from similar to 7.0 to 2.5 mu m, sharp decrease in the dielectric constant from 198 to 88 and an increase in the electrical conductivity from 3.16 x 10(-10) to 5.0 x 10(-9) (Omega cm)(-1), respectively. The temperature dependent dielectric constant which is found to be frequency invariant in the frequency range of (0.0-2.0 MHz) exhibited a sharp change in the temperature coefficient of dielectric constant at a (doping independent) critical temperature of 395 K. The analysis of the measured data reflects a promising future for this type of pyrochlore to be used in high voltage passive device applications. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Article Citation - WoS: 14Citation - Scopus: 13Enhancement of Electrical Performance of Znse Thin Films Via Au Nanosandwiching(Sciendo, 2020) Qasrawi, A. F.; Taleb, Maram F.In this work, we report the effect of sandwiching of Au nanosheets on the structural and electrical properties of ZnSe thin films. The ZnSe films which are grown by the thermal evaporation technique onto glass and yttrium thin film substrates exhibit lattice deformation accompanied with lattice constant extension, grain size reduction and increased defect density upon Au nanosandwiching. The temperature dependent direct current conductivity analysis has shown that the 70 nm thick Au layers successfully increased the electrical conductivity by three orders of magnitude without causing degeneracy. On the other hand, the alternating current conductivity studies in the frequency domain of 10 MHz to 1800 MHz have shown that the alternating current conduction in ZnSe is dominated by both of quantum mechanical tunneling and correlated barrier hopping of electrons over the energy barriers formed at the grain boundaries. The Au nanosheets are observed to increase the density of localized states near Fermi level and reduce the average hopping energy by similar to 5 times. The conductivity, capacitance, impedance and reflection coefficient spectral analyses have shown that the nanosandwiching of Au between two layers of ZnSe makes the zinc selenide more appropriate for electronic applications and for applications which need microwave cavities.Article Citation - WoS: 3Citation - Scopus: 3Dielectric Dispersion and Energy Band Gap of Bi1.5-x< Solid Solution(Elsevier Science Bv, 2014) Qasrawi, A. F.; Mergen, A.The optical transmittance and reflectance spectra of samarium doped bismuth-zinc-niobium-oxide (BZN) pyrochlore ceramics are investigated in the wavelength range of 200-1050 nm (200-1500 THz). The Sm content in the Bi1.5-xSmxZn0.92Nb1.5O6.92 solid solution significantly alters the optical properties. Therefore, increasing the Sm doping ratio from x=0.10 to x=0.13 decreased the indirect forbidden energy band gap from 3.60 to 3.05 eV. In addition, above 350 THz, increasing the Sin content decreases the dielectric constant values and alters the dielectric dispersion parameters. The dielectric spectra which were evaluated in the frequency range of 200-1500 THz reflected a sharp decrease in the dielectric constant with increasing frequency clown to 358 THz. The spectra reflected a resonance peak at this frequency. Such resonance spectrum is promising for technological applications as it is close to the illumination of 870 am IR lasers that are used in optical communications. The calculated oscillator (E-o) and dispersion (E-d) energies near that critical range (375-425 THz) reflected an increase in both E-o and E-d with increasing Sm content. (C) 2014 Elsevier B.V. All rights reserved.Article Citation - WoS: 7Citation - Scopus: 7Enhancing the Optoelectronic Performance of As2se3< Thin Films Via Ag Slabs Sandwiching(Elsevier Gmbh, 2020) Qasrawi, A. F.; Alharbi, Seham ReefIn 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.Article Citation - WoS: 17Citation - Scopus: 19Synthesis and Characterization of Bi1.5zn0.92< Pyrochlore Ceramics(Elsevier Sci Ltd, 2012) Qasrawi, A. F.; Kmail, Bayan H.; Mergen, A.The morphological, compositional, structural, dielectric and electrical properties of Bi1.5Zn0.92Nb1.5-xSnxO6.92-x/2 ceramics have been investigated by means of scanning electron microscopy (SEM), X-ray energy dispersion spectroscopy (EDS), X-ray diffraction (XRD), temperature and frequency dependent dielectric constant and temperature dependent conductivity measurements for Sn-contents in the range of 0.00 <= x <= 0.60. It was shown that single phase of the pyrochlore ceramics can only be obtained for x <= 0.25. Above this value a ZnO phase appeared in the XRD patterns and SEM micrographs as well. An increase in the lattice constant and in the temperature coefficient of dielectric constant and a decrease in the dielectric constant values with increasing Sn content was observed for the ceramics which exhibited a single phase formation. A temperature dependent but frequency invariant dielectric constant was observed for this type of ceramics. The lowest electrical conductivity and highest dielectric constant was observed for the sample which contains 0.06 Sn. The Bi1.5Zn0.92Nb1.5-xSnxO6.92-x/2 pyrochlore ceramic conductivities are thermally active above 395 K. For temperatures greater than 395 K, the conductivity activation energy which was found to be 0.415 eV for the pure sample increased to 1.371 eV when sample was doped with 0.06 Sn. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Optoelectronic Properties of Ga4se3< Single Crystals(Iop Publishing Ltd, 2008) Qasrawi, A. F.; Gasanly, N. M.; Ilaiwi, K. F.The optoelectronic properties of Bridgman method-grown Ga(4)Se(3)S single crystals have been investigated by means of room temperature electrical resistivity, temperature-dependent photosensitivity and temperature-dependent optical absorption. The photosensitivity was observed to increase with decreasing temperature, the illumination dependence of which was found to exhibit monomolecular recombination in the bulk at 300 K. The absorption coefficient, which was calculated in the incident photon energy range of 2.01-2.35 eV, increased with increasing temperature. Consistently, the absorption edge shifts to lower energy values. The fundamental absorption edge corresponds to an indirect allowed transitions energy gap (2.08 eV at 300 K) that exhibits a temperature coefficient of -95 x 10(-4) eVK(-1).Article Citation - WoS: 4Citation - Scopus: 4Hall Mobility and Photoconductivity in Tlgases Crystals(Amer inst Physics, 2013) Qasrawi, A. F.; Gasanly, N. M.In this work, the fundamental properties of the TlGaSeS single crystals are investigated by means of temperature dependent electrical resistivity and Hall mobility. The crystal photo-responsibility as function of illumination intensity and temperature is also tested in the temperature range of 350-160 K. The study allowed the determination of acceptor centers as 230 and 450 meV below and above 260 K, and recombination centers as 181, 363, and 10 meV at low, moderate, and high temperatures, respectively. While the temperature-dependent Hall mobility behaved abnormally, the photoconductivity analysis reflected an illumination intensity dependent recombination center. Namely, the recombination center increased from 10 to 90 meV as the light intensity increased from 27.9 to 76.7 mW cm(-2), respectively. That strange behavior was attributed to the temporary shift in Fermi level caused by photoexcitation. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775577]Article Citation - WoS: 40Citation - Scopus: 42Design and Electrical Performance of Cds/Sb2< Tunneling Heterojunction Devices(Iop Publishing Ltd, 2018) Khusayfan, Najla M.; Qasrawi, A. F.; Khanfar, Hazem K.In the current work, a tunneling barrier device made of 20 nm thick Sb2Te3 layer deposited onto 500 nm thick CdS is designed and characterized. The design included a Yb metallic substrate and Ag point contact of area of 10(-3) cm(2). The heterojunction properties are investigated by means of x-ray diffraction and impedance spectroscopy techniques. It is observed that the coating of the Sb2Te3 onto the surface of CdS causes a further deformation to the already strained structure of hexagonal CdS. The designed energy band diagram for the CdS/Sb2Te3 suggests a straddling type of heterojunction with an estimated conduction and valence band offsets of 0.35 and 1.74 eV, respectively. In addition, the analysis of the capacitance-voltage characteristic curve revealed a depletion region width of 14 nm. On the other hand, the capacitance and conductivity spectra which are analyzed in the frequency domain of 0.001-1.80 GHz indicated that the conduction in the device is dominated by the quantum mechanical tunneling in the region below 0.26 GHz and by the correlated barrier hopping in the remaining region. While the modeling of the conductivity spectra allowed investigation of the density of states near Fermi levels and an average scattering time of 1.0 ns, the capacitance spectra exhibited resonance at 0.26 GHz followed by negative differential capacitance effect in the frequency domain of 0.26-1.8 GHz. Furthermore, the evaluation of the impedance and reflection coefficient spectra indicated the usability of these devices as wide range low pass filters with ideal values of voltage standing wave ratios.Article Citation - WoS: 6Citation - Scopus: 6Characterization of the A1/Ge/In2Se3/Ga2S3/Al hybrid tunneling barriers designed for Gigahertz/Terahertz applications(Elsevier Science Sa, 2018) Qasrawi, A. F.; Omareya, Olfat A.In the current work, we report the design and performance of a tunneling amorphous thin film hybrid device made of Ge/In2Se3/Ga2S3 sandwiched between two aluminum thin films. Each of the stacked semiconducting layers are of 200 nm thicknesses. The hybrid device which is composed of a p-n junction between two Schottky shoulders is designed to have two valence band offsets of 0.59 and 0.84 eV at the Ge/In2Se3 and at In2Se3/Ga2S3 interfaces, respectively The offsets which caused two quantum confinements forces the device to exhibit field effect assisted thermionic and thermionic transport mechanisms under the reverse and forward biasing conditions, respectively. When an alternating current signal is imposed between the terminals of the device, the device conducted by the quantum mechanical tunneling of charge carriers and by the correlated barrier hopping above and below 0.180 GHz, respectively. The hybrid structure are also observed to exhibit series and parallel resonance at the switching frequency between the two conduction mechanisms. It also exhibited negative differential capacitance effect in the frequency domain of 0.18-1.80 GHz. For the Al/Ge/In(2)Se3/Ga2S3/Al hybrid structure the microwave cutoff frequency reached 100 GHz. The latter value is promising as it indicates the ability of using the device as fast switches and microwave/Tera wave traps.
