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Article Citation - WoS: 2Citation - Scopus: 2Performance of Ge-Sandwiched Gase Layers(Springer, 2018) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Abdallah, Maisam M. A.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringIn the current work, we report the effect of sandwiching Ge between two stacked layers of GaSe. The GaSe and Ge-sandwiched GaSe were subjected to x-ray diffraction, optical spectrophotometry and impedance spectroscopy measurement and analysis. The presence of a Ge layer between two layers of GaSe was observed to cause uniform deformation and increase the absorption of light by GaSe. The response of the dielectric constant to incident light was also significantly enhanced by Ge sandwiching. In addition, Drude-Lorentz modeling of the imaginary part of the dielectric constant revealed that the layer of Ge layer between GaSe layers increased the drift mobility from 30.76 cm(2)/Vs to 52.49 cm(2)/Vs. It also enhanced the plasmon frequency without altering the free carrier density. Moreover, Ge improved the band filtering features of GaSe. In particular, it enhanced the sensitivity of the impedance response to the incident signal and increased the return loss factor of GaSe when it was used as a high band pass filter.Article Citation - WoS: 2Citation - Scopus: 2Dielectric and Optoelectronic Properties of Inse/Cds Heterojunctions(Springer, 2018) Abusaa, M.; Qasrawi, A. F.; Shehada, Sufyan R.The effect of an InSe substrate on the structural, optical and dielectric properties of CdS/CdSe heterojunctions prepared by physical vapor deposition technique under vacuum pressure of 10(-8) bar are reported. The structural analysis carried out by x-ray diffraction revealed a strained type of growth of the CdS/CdSe heterojunction onto the InSe along the axis of the hexagonal lattice. The lattice mismatches and strained nature of the heterojunctions associated with the InSe participation causes a quantum confinement that results in a red shift in the energy band gap, enhanced near infrared (IR) light absorbability, and valence band offsets of 0.62eV and 0.53eV for the InSe/CdS and CdS/CdSe interfaces, respectively. In addition, a pronounced enhancement in the real part of the dielectric constant by 2.5 times is observed at 1.25eV. Furthermore, the Durde-Lorentz modeling of the optical conductivity of the CdS/CdSe and InSe/CdS/CdSe reveals significant increases in the drift mobility values from 43.8cm(2)/Vs at the CdS/CdSe interface to 100.0cm(2/)Vs upon replacement of glass by an amorphous InSe substrate. The other optical conduction parameters including the free carrier scattering time at the femtosecond level, the plasmon frequency and the free carrier density are also improved accordingly. The photocurrent illumination intensity dependence for the studied system showed that the presence of InSe increases the photocurrent values and changes the recombination mechanism from sublinear at the surface to trap-assisted recombination. The smart feature of the InSe/CdS/CdSe system is that the structurally controlled quantum confinement results in having mobile photocarriers arising from the enhanced absorbability and large dielectric response in the IR region.Article Citation - WoS: 4Citation - Scopus: 3Effect of Au/Ge Substrate on the Properties of Gase(Elsevier Gmbh, 2018) Qasrawi, A. F.; Abdallah, Maisam M. A.In this work, the effect of glass/Ge and Au/Ge substrate on the structural, optical and electrical properties of the GaSe thin films is investigated by means of X-ray diffraction, ultraviolet-visible light spectrophotometry and impedance spectroscopy techniques, respectively. While the glass/Ge, glass/GaSe and glass/Ge/GaSe are observed to exhibit amorphous nature of structure, the Au/Ge, and Au/Ge/GaSe are of polycrystalline nature. The formation of the Ge/GaSe interface exhibited high conduction band offset of value of 0.90 eV and enhanced the light absorbability of GaSe at 1.47 eV by 80 times. In addition, the modeling of the dielectric spectra for the Ge/GaSe interface revealed optical conductivity parameters presented by scattering time at femtosecond level and improvement of the drift mobility. Moreover, the impedance spectroscopy measurements have shown that with the increasing frequency, the Au/Ge/GaSe/Yb interface exhibit increasing trend of variation in the resistance causing high impedance mode associated with negative capacitance values below 1300 MHz. The effect is completely reversed in the higher range of frequency. These features of the Ge/GaSe interface nominate it as plasmonic interface, microwave cavities and as voltage amplifiers in low power nanoscale devices. (C) 2018 Elsevier GmbH. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 4Structural and Optical Properties of the Zns/Gase Heterojunctions(Iop Publishing Ltd, 2017) Alharbi, S. R.; Abdallaha, Maisam M. A.; Qasrawi, A. F.In the current work, the ZnS/GaSe thin film heterojunction interfaces are experimentally designed and characterized by means of x-ray diffraction, scanning electron microscopy, energy dispersion spectroscopy and optical spectroscopy techniques. The heterojunction is observed to exhibit physical nature of formation with an induced crystallization of GaSe by the ZnS substrate. For this heterojunction, the hot probe technique suggested the formation of a p-ZnS/n-GaSe interface. In addition, the designed energy band diagram of the heterojunction which was actualized with the help of the optical spectrophotometric data analysis revealed a respective conduction and valence band offsets of 0.67 and 0.73 eV. On the other hand, the dielectric dispersion analysis and modeling which was studied in the frequency range of 270-1000 THz, have shown that the interfacing of the ZnS with GaSe strongly affects the properties of ZnS as it reduces the number of free carriers, shifts down the plasmon frequency, increases the charge carrier scattering time and results in higher values of drift mobility at Terahertz frequencies.
