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    (An - Najah National University, 2023-05-15) Ayham Anwar Ahmad Shaer
    The anisotropic quantum dot (QD) Hamiltonian has been solved using the diagonalization method in the presence of a perpendicular magnetic field and Gaussian impurity, considering both types of spin-orbit interaction (SOI): Rashba and Dresselhaus. The diagonalization process has been carried out using the one-dimensional harmonic oscillator basis. The acceptor impurity's presence significantly affects the system's eigensolution, specifically causing an interesting level crossing between the states and changing the ground state order. Furthermore, the impurity's strength, position, and spatial stretch have been investigated, and the result shows that the impurity plays an important role in manipulating the QD properties. The magnetization and magnetic susceptibility as important quantities of the QD system made from InAs are studied. The results show a diamagnetic-paramagnetic phase transition at low temperatures due to the impurity presence. This magnetic transition strongly correlates with the impurity profiles (strength, position, and influence domain), magnetic field, and temperature. As the strength of the impurity increases, the diamagnetic-paramagnetic transition occurs at a lower value of the magnetic field. In addition, the effective Lande factor g of the system has been studied. The result shows that, as the electric field increases, the Rashba SOI increases |g|, while the Dresselhaus SOI reduced |g| of the QD. Furthermore, in the presence of both types of SOI, increasing the electric field enhances the |g| since in the InAs material, the Rashba SOI dominates the Dresselhaus SOI. The result emphasizes the role of Rashba SOI in spintronics devices. The confinement strength effect on the g has been investigated, the g shows a peak value at particular confinement strength. In addition, the anisotropy of the QD shows a significant role in controlling g. The density of states of the system has also been computed to physically describe the impact of each system parameter on the energy spectrum. As the magnetic field turns on, the figures demonstrate how the anisotropy of the confinement potential also causes the harmonic oscillator symmetry to be broken.
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    (An Najah National University, 2022-02-27) Mahmoud Elaiyan Al-Masri, Khadejah
    In this study, we investigate the structural, electronic, magnetic and elastic properties of the normal and inverse Heusler Sc2TiAl and Sc2TiSi compounds using a full potential linearized augmented plane wave (FP-LAPW) method, within the density functional theory. The band structure and DOS calculations are made within the generalized gradient approximation (GGA) and modified Becke Johnson approaches (mBJ-GGA), employed in the Wien2K code. The density of states (DOS) and band structure (BS) show metallic nature. We calculate the structural properties such as the lattice constants, bulk moduli and elastic properties like Poisson ratio v, shear modulus S, Young modulus (Y) and B/s ratio. Results are in agreement with previous studies so these properties provide a road map for its possible uses in electronic devices.
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    Characterization of Dissolved Organic Matter in Wadi Al-Badan using Fourier Transform Infrared Microspectroscopy at SESAME
    (An Najah National University, 2019-05-15) Atari, Amal
    Wadi Al-Badan is one the Faria catchment tributaries that drains from the eastern parts of Nablus city. Water quality in the Wadi is being deteriorated due to the continuous effluent of untreated wastewater from the city of Nablus. Contamination by Dissolved Organic Matter (DOM) is a predominant problem in the Wadi which in turn can activate microorganisms growth in the Wadi flow. The presences of microbiological contaminants will potentially contaminate the surface water and groundwater resources in the catchment. The contaminated water will endanger the local consumers mainly those use water for drinking purposes. Therefore, it is important to study and characterize the DOM in Wadi Al-Badan. Selected water samples were collected along the main Wadi (stream flow) and analyzed using two methods: firstly, traditional analysis that was conducted at the labs of the Water and Environmental Studies Institute (WESI) of An-Najah National University and secondly, using FTIR analysis at Synchrotron light for Experimental Science and Applications (SESAME) in Jordan. For FTIR analysis, after survey spectra were obtained, they were analyzed using Essential FTIR software, which allows for identifying various peaks of DOM components. FTIR results showed that the considerable presences of different compounds of DOM are: Amide, aromatic, aliphatic, and carbohydrate compounds. In addition, DOM chemical compositions are affected by DOM inputs from the surrounding environment and natural purification that take place along the main Wadi. The study demonstrated that FTIR method could be used to characterize DOM in aquatic system, as well as to track the potential sources of DOM in Wadi flow.
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    Development of Efficient Photovoltaic Solar Cells’ Various Models
    (Aya Mahmoud Abu Baker, 2019-03-21) Abu Baker, Aya
    This thesis deals with three different types of photovoltaic (PV) cells namely monocrystalline silicon and polycrystalline silicon and organic PV cells. We studied four models of PV cells equivalent circuits for each of mono- and polycrystalline silicon cells by QUCS software. The input parameters were extracted from the datasheet of the cells. The main goal of this research is to conclude the most efficient model of DC PV cells that gives the highest maximum power point. This work also deals with the main factors affecting the behavior of the PV cell: the cell temperature and solar irradiance. I-V characteristic curves will be drawn properly under the variation of temperature and irradiance. Depending on varying the models of PV cells, cell temperature and irradiance we saw how efficiency and different parameters of the cell will be varied. This thesis opens up a new field which is the organic solar cells devices or third generation of PV cells devices. The electrical simulation of an organic bulk heterojunction (BHJ) PV cell based on P3HT:PCBM as an active layer was done using GPVDM software under STC. The conversion efficiency of organic BHJ cells is studied under changing the thickness of the active layer. Furthermore, the current density-voltage characteristics were obtained under changing series resistance value. The simulation results confirmed, as expected, that monocrystalline silicon solar cells are more efficient than polycrystalline silicon solar cells but polycrystalline solar cells have higher quality than monocrystalline solar cells. It was concluded also that the non-crystalline solar cells are not as efficient as the crystalline ones but they are cheaper.
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    FP-LAPW Study of Structural, Electronic, Elastic and Optical Properties of Alkali Hydrides Compounds XH (X= Li, Na, K, Rb, Cs)
    (An-Najah National University, 2018-04-18) Jaradat, Raed
    Based on the density functional theory, the full-potential linearized augmented plane wave (FP-LAPW) method has been carried out to determine the structural stability of different crystallographic phases, the pressure-induced phase transition, the electronic properties, the elastic constants and their related properties, the mechanical properties, the thermodynamic properties as well as the optical properties of LiH, NaH, KH, RbH and CsH compounds. The rocksalt (RS), zincblende (ZB), cesium chloride (CsCl) and wurtzite (WZ) structures are considered. The Perdew, Burke and Ernzerhof Generalized Gradient Approximation (PBE-GGA) approach was used for the exchange-correlation potential to compute the equilibrium structural parameters, transition pressure, elastic constants and their related properties, the mechanical properties as well as the thermodynamic properties. The PBE-GGA and modified Becke-Johnson (mBJ-GGA) schemes have been used for the exchange-correlation potential to calculate the band structures and optical properties. The alkali hydrides lattice constant increases as going from Li to Cs in the periodic table, while bulk modulus decreases. The calculated band structures using the mBJ-GGA approach have an insulating nature for these compounds in all the considered structures, except the LiH and CsH in CsCl structure, which show a semi-conducting behavior. The calculated elastic constants for alkali hydrides in the four structures RS, CsCl, ZB and WZ at ambient pressure are mechanically stable, except LiH and NaH in CsCl structure. The mBJ-GGA scheme is found to be more accurate than PBE-GGA in computing the energy-band gap and optical properties compared to the experimental results. The elastic constants (C11, C44, B) and their related properties in the RS structure are increasing with increasing pressure, C12 decreases as the pressure increases indicates that these compounds are unstable under high pressure, and the RS structure transforms to CsCl structure. Elastic constants, bulk modulus, Shear modulus (stiffness) and Debye temperatures of these compounds decrease as going from Li to Cs in the periodic table. These compounds in the RS structure are more mechanically stronger at ambient conditions. Alkali hydrides except the LiH and CsH in CsCl structure are suitable as dielectric compounds; they have a wide direct energy band gap. Alkali hydrides have a wide absorption region, on the other hand NaH and RbH absorption is very huge compared with LiH, KH and CsH absorption. NaH and RbH are excellent absorbent materials; maximum absorption regions are located in the middle ultraviolet (MUV) region and far ultraviolet (FUV) region. LiH, RbH and CsH compounds are also found to be a wide direct energy band gap; therefore, they could be suitable for the optoelectronic UV device applications. The absorption coefficient α(w), imaginary part of dielectric constant ε_2 (w) and the extinction coefficient k(w) for alkali compounds vary in the same way. The calculated ground state parameters for these compounds in each structure are well compared with the available theoretical and experimental results, and most of them are in good agreement with other calculations and experimental measurements.