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Electrical Characterization of Al/Ta_2O_5/Al Structures Grown by Electron Beam Deposition

100%
Yahia I., Farag A.
Acta Physica Polonica A
|
2014
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vol. 125
|
issue 5
1191-1196
EN
We report study of current density-voltage (J-V) and capacitance-voltage (C-V) characteristics of Al/Ta_2O_5/Al metal-insulator-metal structures prepared by electron beam deposition. At low bias voltages the J-V characteristics of Al/Ta_2O_5/Al structures show ohmic conduction. At higher voltages the conductivity becomes limited by space charge. The space charge limited conductivity is due to carrier trap centers located within the energy gap of Ta_2O_5. The distribution of the trap appears to be exponential above the valence band. Basing on the comparison of the measured temperature dependences of the current density with the theoretical model one can determine important material parameters, such as the trap density. The density of states at the Fermi level N(E_{F}) for the Ta_2O_5 film is found to be 2.75 × 10^{19} eV^{-1} cm^{-3}. The capacitance-voltage-temperature (C-V-T) characteristics of Al/Ta_2O_5/Al structures were carried out in the bias range -5 to +5 V and at temperatures from 300 to 550 K. The capacitance of Al/Ta_2O_5/Al structures increases with the increasing temperature.
2
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Ground States of Helium Atom and Hydrogen Negative Ion in the Presence of Magnetic Field Using Variational Monte Carlo Technique

81%
Doma S., Shaker M., Farag A., El-Gammal F.
Acta Physica Polonica A
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2014
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vol. 126
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issue 3
700-705
EN
Using variational Monte Carlo method, we calculated the 1^1 0^{+} state energies, the derivatives of the total energy and the ionisation energies of the helium atom, and hydrogen negative ion in the presence of magnetic field regime between 0 a.u. and 10 a.u. Our calculations are based on using two types of compact and accurate trial wave functions used before to calculate energies in the absence of magnetic field. Our results are in good agreement with the most recent previous accurate values and also with the exact values.
3
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Influence of Temperature and Illumination on the Electrical Characteristics of Nanocrystalline Cu_2S Based Heterojunctions for Photodetector Application

81%
Soliman H., Farag A., Saadeldin M., Sawaby K.
Acta Physica Polonica A
|
2015
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vol. 127
|
issue 6
1688-1693
EN
In this work, heterojunctions of Cu_2S/p-Si were prepared by high vacuum thermal evaporation technique and examined as a photodetector structure. The dark current-voltage (I-V) characteristics of the heterojunctions measured at different temperatures ranging from 303 to 373 K were investigated. The predominant conduction mechanisms, series resistance, ideality factor and potential barrier height were determined. The downward curvature at sufficiently large voltages in the I-V characteristics is caused by the effect of series resistance R_{s}. The ideality factor obtained from I-V characteristics is larger than unity which can be attributed to the presence of a thin interfacial insulator layer between the metal and semiconductor. The photocurrent properties of the device under reverse bias using various illuminations were also explored for checking the validity of photodetector application of the studied device. The responsivity of light for the device under reverse bias confirms that the Cu_2S/p-Si heterojunctions are valid for photodetector application. Moreover, these results suggest that the fabricated diode can be used for optical sensor applications. The capacitance-voltage characteristics of diode were also investigated at high frequency of 1 MHz.
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