Browsing by Author "Kmail, Renal R. N."

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Citation - WoS: 5
Citation - Scopus: 6
Mechanical and Electrical Properties of Bi_1.5-xla_{x< Pyrochlore Ceramics}
(Springer, 2016) Qasrawi, A. F.; Kmail, Renal R. N.; Mergen, A.; Genc, Seval
The physical properties of Bi1.5-xLaxZn0.92Nb1.5O6.92 solid solutions are investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy (EDS), and temperature dependent relative permittivity and electrical resistivity measurements. The La content which was varied from 0.10 to 0.60 is found to be solvable up to 0.21. Further increase in the amount of the La content caused the appearance of Bi0.4La0.6O1.5, LaNbO4, and ZnO minor phases in the pyrochlore matrix. While the lattice parameter and the theoretical, bulk and relative density are hardly affected by the increase in the La content, the strain, the dislocation density and the crystallite size are remarkably varied. The relative permittivity and temperature coefficient of relative permittivity are found to be sensitive to the La-Content. The electrical resistivity is observed to be temperature invariant below 390 K. It exhibits an insulator-semiconductor transition property at a critical temperature that increases with the increasing La content. Such observation is assigned to the increase in the dislocation density, which arises from the increment in the La content. The activation energies of the doped ceramics, which are determined from the electrical resistivity analysis are found to be similar to 1.12-1.00 eV.
Citation - WoS: 11
Citation - Scopus: 10
Optical Conduction in Amorphous Gase Thin Films
(Elsevier Gmbh, 2016) Qasrawi, A. F.; Khanfar, Hazem. K.; Kmail, Renal R. N.
In this work, the optical conduction mechanism in GaSe thin films was explored by means of dielectric spectral analysis in the 270-1000 THz range of frequency. The GaSe films which are found to be amorphous in nature are observed to follow the Lorentz approach for optical conduction. The modeling of the optical conductivity which takes into account the damped electronic motion resulting from the collision of photogenerated carriers with impurities, phonons and other damping sources allowed determining the optical conduction parameters. Particularly, an average carrier scattering time, a free carrier density, a reduced resonant frequency, a field effect mobility and an electron bounded plasma frequency of 0.142 (fs), 1.7 x 10(19) (cm(-3)), 875.8 (THz), 1.25 (cm(2)/Vs) and 82.8 (THz), respectively, were determined. These parameters are promising as they indicate the applicability of GaSe in the technology of mid-infrared plasmonic nanoantennas. In addition, the dielectric optical signal which displayed a resonance peak at 500 THz seems to be attractive for use in passive modes operating optoelectronic devices like field effect transistors as they exhibit an increasing signal quality factor with decreasing incident light frequency (C) 2016 Elsevier GmbH. All rights reserved.
Citation - WoS: 7
Citation - Scopus: 7
Physical Design and Dynamical Analysis of Resonant-Antiresonant Ag/MgO/GaSe/Al Optoelectronic Microwave Devices
(Springer, 2015) Kmail, Renal R. N.; Qasrawi, A. F.
In this work, the design and optical and electrical properties of MgO/GaSe heterojunction devices are reported and discussed. The device was designed using 0.4-mu m-thick n-type GaSe as substrate for a 1.6-mu m-thick p-type MgO optoelectronic window. The device was characterized by means of ultraviolet-visible optical spectrophotometry in the wavelength region from 200 nm to 1100 nm, current-voltage (I-V) characteristics, impedance spectroscopy in the range from 1.0 MHz to 1.8 GHz, and microwave amplitude spectroscopy in the frequency range from 1.0 MHz to 3.0 GHz. Optical analysis of the MgO/GaSe heterojunction revealed enhanced absorbing ability of the GaSe below 2.90 eV with an energy bandgap shift from 2.10 eV for the GaSe substrate to 1.90 eV for the heterojunction design. On the other hand, analysis of I-V characteristics revealed a tunneling-type device conducting current by electric field-assisted tunneling of charged particles through a barrier with height of 0.81 eV and depletion region width of 670 nm and 116 nm when forward and reverse biased, respectively. Very interesting features of the device are observed when subjected to alternating current (ac) signal analysis. In particular, the device exhibited resonance-antiresonance behavior and negative capacitance characteristics near 1.0 GHz. The device quality factor was similar to 10(2). In addition, when a small ac signal of Bluetooth amplitude (0.0 dBm) was imposed between the device terminals, the power spectra of the device displayed tunable band-stop filter characteristics with maximum notch frequency of 1.6 GHz. The energy bandgap discontinuity, the resonance-antiresonance behavior, the negative capacitance features, and the tunability of the electromagnetic power spectra at microwave frequencies nominate the Ag/MgO/GaSe/Al device as a promising optoelectronic device for use in multipurpose operations at microwave frequencies.