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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 - Scopus: 1Samarium and Yttrium Doping Induced Phase Transitions and Their Effects on the Structural, Optical and Electrical Properties of Nd2sn2< Ceramics(Iop Publishing Ltd, 2019) Saleh, Adli A.; Qasrawi, A. F.; Hamamera, Hanan Z.; Khanfar, Hazem K.; Yumusak, G.In this work, the effects of Sm+3 and Y+3 doping onto the structural, optical and electrical properties of Nd2Sn2O7 are investigated. An atomic content of 3.49% and 4.29% of Sm and Y, respectively, were sufficient to alter the physical properties of the Nd2Sn2O7. Particularly, the Y+3 ionic substitution decreased the lattice constant, narrows the energy band gap, changed the conductivity type from n- to p- type and increased the electrical conductivity by 73 times without changing the cubic nature of structure of the pyrochlore ceramics. On the other hand, Sm+3 ionic substitutions changed the cubic structure to hexagonal or trigonal and forced optical transitions in the infrared range of light. The energy band gap shrunk from 3.40 to 1.40 eV, the defect density is reduced and the electrical conductivity increased by 47 times via Sm doping. These doping agents' makes the neodymium stannate pyrochlore ceramics more appropriates for optoelectronic applications.Article Citation - WoS: 2Citation - Scopus: 2Post Annealing Effects on the Structural and Optical Properties of Moo3 Sandwiched With Indium Slabs(Iop Publishing Ltd, 2019) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Kmail, Haifaa K.; AbuSaa, M.; Khanfar, Hazem K.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringMolybdenum trioxide thin films are prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar through insertion of indium slabs of thickness of 200 nm between layers of MoO3 and annealing the produced films in the air atmosphere at 250 degrees C for one hour. The films are studied by means of x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, and optical spectrophotometry techniques. The structure of the films is found to be composed monoclinic MoO3, tetragonal indium and cubic In2O3. The phase percentage of In2O3 in the films increased to 26.3% upon annealing at 250 degrees C. The annealing process increased the microstrain, the defect density, the oxygen atomic content and lowered the crystallites and grains sizes in the films. Optically, two energy band gaps of values of 3.20 and 1.70 eV were detected for the MoO3/In/MoO3 system. In addition, nonlinear dielectric response associated with wide range of tunability in the dielectric constant value, in the optical conductivity and in the terahertz cutoff frequency was observed in the near IR spectral range. The annealing of the samples improved the nonlinearity in these parameters and make MoO3/In/MoO3 system more appropriates for optoelectronic technology applications as terahertz cavities and frequency convertors.
