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Article
Analytical Study of near Mobility Edge Density of States of Hydrogenated Amorphous Silicon
دراسة تحليلية لكثافة الحالات للسليكون العشوائي المهدرج قرب حافة التحركية

Author: Abdullah Ibrahim Abbo عبدالله ابراهيم عبو
Journal: Baghdad Science Journal مجلة بغداد للعلوم ISSN: 20788665 24117986 Year: 2014 Volume: 11 Issue: 3 Pages: 1243-1249
Publisher: Baghdad University جامعة بغداد

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Abstract

Experimental results for the density of states of hydrogenated amorphous silicon due to Jackson et al near the valence and conduction band edges were analyzed using Levenberg-Marquardt nonlinear fitting method. It is found that the density of states of the valence band and the conduction band can be fitted to a simple power law, with a power index 0.60 near the valence band edge, and 0.55 near the conduction band edge. These results indicate a modest but noticeable deviation from the square root law (power index=0.5) which is found in crystalline semiconductors. Analysis of Jackson et al density of states integral J(E) data over about (1.4 eV) of photon energy range, showed a significant fit to a simple power law with a power index of 2.11 close to that predicted from the density of states fitting results 2.15

تم تحليل النتائج التجريبية لكثافة الحالات للسليكون العشوائي المهدرج لجاكسون وجماعته قرب حافتي التكافؤ و التوصيل باستخدام طريقة ليفينبرك وماركوارد للموائمة غير الخطية. لقد وجد ان توزيع كثافة الحالات قرب حافتي حزمة التكافؤ والتوصيل يتوائم مع قانون قوى بسيط بمعامل قوى 0.60 لحزمة التكافؤ و 0.55 لحزمة التوصيل. هذه النتائج تشير الى انحراف معتدل لكن ملحوظ عن قانون الجذر التربيعي (معامل قوى0.5 ) الذي ينطبق في اشباه الموصلات البلورية.تم تحليل بيانات حاكسون وجماعته لتكامل كثافة الحالات J(E) في مدى يغطي1.4 eV من طاقة الفوتون وقد اظهرت النتائج توائما جيدا مغ قانون قوى بسيط بمعامل قوى 2.11 قريبا من ذلك المتوقع من نتائج الموائمة مع بيانات كثافة الحالات 2.15 .


Article
First Principle Calculation of Pressure-Induced Phase Transition and Band Structure of Gallium Phosphide

Author: Kh. Kabita et al.
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2013 Volume: 9 Issue: 4 Pages: 17-20
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

A first principle study of the electronic, structural and phase transition of the III-V binary compound semiconductor gallium phosphide (GaP) is performed under the framework of density functional theory (DFT). Structural transformation from the zinc-blende (ZB) to rocksalt (RS) structure is observed at a pressure of about 21.9 GPa and the dependence of the volume decrease of ZB to RS structure at the transition pressure is 14.11% . The variation of the energy band gap, elastic constants and debye’s temperature with pressure are also obtained successfully. Our results are found to be in consistent with other experimental and theoretical results.


Article
The Resonance Tunneling Process in the Scanning Tunneling Microscope with Carbon Nanotube as a Tip

Authors: Jenan M.AL-Mukh --- Alaa Khalid
Journal: Journal of Basrah Researches (Sciences) مجلة ابحاث البصرة ( العلميات) ISSN: 18172695 Year: 2018 Volume: 44 Issue: 1A Pages: 76-95
Publisher: Basrah University جامعة البصرة

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Abstract

In our work we present an integrated calculation model to investigate the possibility of using carbon nanotubes as a tip for the scanning tunneling microscope. Our model takes into consideration the electronic properties of the substrate and tip that fabricated by using carbon nanomaterials . since we calculated the hybridization function and the quantum shift(as well as the assistant function) due to coupling between the molecule and the tip and the substrate . This calculation are utilized to calculate the local density of states on the molecule . We firstly studied the effect of all the properties of the carbon nanotube tip , since different carbon nanotubes chiral and achiral , metallic and semiconductor with different diameters are considered . Also , we calculated the transport properties for the used system (substrate - molecule – carbon nanotube tip) , these calculations can be considered as an additional step to enhance our results . We conclude that the carbon nanotube tip is not suitable for investigation in the most cases ,since that depends on the molecule effective energy level position with respect to the Van Hove (V.H) singularities in the electronic density of states of the carbon nanotube . And as the normal distance between the tip and the molecule is one of the most important experimental parameters that enhance the process of investigation , the effect of the tip distance on the process of investigation is studied for the carbon nanotube (12,0) . According to our calculations , it's concluded that it is possible to get the exact density of states by controlling the distance which is a function of the molecule effective energy level position .


Article
TIME DEPENDENT SPIN TRANSPORT THROUGH T – SHAPED DOUBLE QUANTUM DOTS EMBEDDED BETWEEN TWO (HALF – METALLIC ScC BULK) LEADS

Authors: MAGED A. NATTIQ --- JENAN M. Al-MUKH --- JABBAR M. KHALAF Al-ZYADI
Journal: Journal of Basrah Researches (Sciences) مجلة ابحاث البصرة ( العلميات) ISSN: 18172695 Year: 2019 Volume: 45 Issue: 2A Pages: 187-201
Publisher: Basrah University جامعة البصرة

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Abstract

For the experimental and theoretical importance of the time – dependent spin transport through quantum dots structures, the electromagnetic field–assisted spin transport through T–shaped double quantum dots embedded between two not normal leads are studied and analyzed. The time – dependent Hamiltonian, that describes the device, follows the tight binding scheme by taking all the spin dependent coupling interactions between the subsystems into consideration. The theoretical treatment is accomplished using the time – evolution operator approach, since the equations of motion in the interaction representation for the time – evolution operator matrix elements are derived. The thirty two intgro-differential equations of motion for both spin are solved numerically by using sixth order Runge Kutta method, since the error is checked in each step of time. The energy dependent calculations are achieved by considering the density of states of the not normal leads. While the adiabatic approximation is used to treat the effects of the external electromagnetic field characteristic (frequency and amplitude) theoretically. In concern to the not normal leads, the study concentrated the first-principles full-potential linearized augmented plane-wave method (FPLAPW), this method depends on the use of the density functional theory to examine the structural, magnetic, and electronic characteristics of the bulk of Zinc-blende ScC. This study has proven that both of the bulk ZB ScC is half- metallic ferromagnet at an equilibrium lattice constant of (0.5121 nm). The main goal of our study is to investigate the effects of the electromagnetic field on the T–shaped double quantum dots device, so all the electronic properties of the device as well as the electromagnetic field parameters are taken into consideration in our treatment. The role of the field frequency and the spin dependent coupling interaction are well analyzed and explained for the ScC bulk leads.


Article
Statistical Study of Nuclear Energy Levels for 6 Particles in The Nuclear N82 Model Space

Authors: Adel K. Hamoudi --- Shatha F. Murad
Journal: Iraqi Journal of Science المجلة العراقية للعلوم ISSN: 00672904/23121637 Year: 2018 Volume: 59 Issue: 4C Pages: 2225-2233
Publisher: Baghdad University جامعة بغداد

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Abstract

The statistical fluctuations of nuclear excitation energies in nucleus are investigated. This nucleus is described as a core of with 6 active protons move in the space of The OXBASH shell-model program together with the interaction of are used to obtain the excitation energies in To reflect the transition from regular (ordered) to chaos in , we consider different strengths parameter to the off diagonal elements of The level density for the states is found to have a Gaussian shape, which is in agreement with the predicted studies for a many-body system with two-body residual interaction. Both distributions for the level spacing and statistics show an ordered performance at strength parameter a chaotic performance at and an in-between situation at

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