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Structural and Optical Properties of GaAs_(0.5)Sb_(0.5) and In_(0.5)Ga_(0.5)As_(0.5)Sb_(0.5):ab initio Calculations for Pure and Doped Materials

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Chinese Physics Letters 2012年第3期29卷 193-196页

作者： Mazin SH.Othman Khudheir A.Mishjil Nadir F.Habubi Department of General Science Faculty of EducationSoran UniversitySoran-ErbilIraq Department of Physics College of EducationAl-Mustansiriyah UniversityIraq

We perform a first-principles study to evaluate the structural,electronic and optical properties of GaAs_(x)Sb_(1-x) ternary and In_(y)Ga_(1-y)As_(x)Sb_(1-x) quaternary semiconductor alloys up to x=0.5,y=*** employ the Perdew-Burke-Ernzerhof form of the generalized gradient approximation(GGA)within the framework of density functional theory(DFT)by using a simulation *** are carried out in different *** these alloys,lattice parameters and optical band gap energy are *** optical band gaps varywith increasing and decreasing As and In concentrations,*** optical conductivity,absorption and the real part of the dielectric function ε1(ω) are *** results agree well with the theoretical and experimental data available in the literature.

关键词： alloys quaternary ternary

Ab Initio Study on Hypothetical Silver Nitride

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Chinese Physics Letters 2008年第6期25卷 2154-2157页

作者： DELIGOZ Enginl COLAKOGLU Kemal CIFTCI Yasemin Oztekin Department of Physics Aksaray University 68100 Aksaray Turkey Department of Physics Gazi University Teknikokullar 06500 Ankara Turkey

We perform the ab initio calculations based on norm-conserving pseudopotentials and density functional theory to investigate the structural, elastic, and thermodynamical properties for silver nitride （AgN） compound that is a member of the 4d transition metal group and has not been synthesized yet. The obtained results are compared with the other available theoretical data, and the agreement is, generally, quite good. We also present the pressure-dependent behaviour of some mechanical and thermodynamical properties for the same compounds.

关键词： ELASTIC PROPERTIES 1ST-PRINCIPLES CALCULATIONS CONSTANTS STABILITY MODEL

Comparative study of the electrical properties of Au/n-Si(MS) and Au/Si_3N_4 /n-Si(MIS) Schottky diodes

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Chinese Physics B 2013年第6期22卷 627-632页

作者： Adem Tataroglu Department of Physics Faculty SciencesGazi University06500AnkaraTurkey

In this paper, the electrical parameters of Au/n-Si （MS） and Au/Si3N4/n-Si （MIS） Schottky diodes are obtained from the forward bias current-voltage （I-V） and capacitance-voltage （C-V） measurements at room temperature. Experimental results show that the rectifying ratios of the MS and MIS diodes at ± 5 V are found to be 1.25 ×103 and 1.27 ×104, respectively. The main electrical parameters of the MS and MIS diodes, such as the zero-bias barrier height （rbBo） and ideality factor （n）, are calculated to be 0.51 eV （I-V）, 0.53 eV （C-V）, and 4.43, and 0.65 eV （I-V）, 0.70 eV （C-V）, and 3.44, respectively. In addition, the energy density distribution profile of the interface states （Nss） is obtained from the forward bias I-V, and the series resistance （Rs） values for the two diodes are calculated from Cheung＇s method and Ohm＇s law.

关键词： Au/n-Si and Au/Si3N4/n-Si type diodes I-V and C-V measurements ideality factor barrier height

Electronic structure calculations of rare-earth intermetallic compound YAg using ab initio methods

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Journal of Rare Earths 2009年第4期27卷 664-666页

作者： S.Ugur G.Ugur F.Soyalp R.Ellialt1oglu Department of Physics Gazi University Teknikokullar Ankara 06500 Turkey Department of Physics Yüzüncü Yll University Zeve Kampüsü Van 65080 Turkey Department of Physics Engineering Hacettepe University Beytepe Ankara 06800 Turkey

The structural, elastic and electronic properties of YAg-B2（CsCl） were investigated using the first-principles calculations. The energy band structure and the density of states were studied in detail, including partial density of states （PDOS）, in order to identify the character of each band. The structural parameters （lattice constant, bulk modulus, pressure derivative of bulk modulus） and elastic constants were also obtained. The results were consistent with the experimental data available in the literature, as well as other theoretical results.

关键词： YAg electronic band structure density of states elastic constants ab initio rare earths

Structural,electronic and elastic properties of YCu from first principles

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Journal of Rare Earths 2009年第4期27卷 661-663页

作者： G.Ugur M.ivi S.Ugur F.Soyalp R.Ellialt1oglu Department of Physics Gazi University Teknikokullar Ankara 06500 Turkey Department of Physics Yüzüncü Yll University Zeve Kampüsü Van 65080 Turkey Department of Physics Engineering Hacettepe University Beytepe Ankara 06800 Turkey

The structural, electronic and elastic properties of YCu compound in the B2 （CsCl） phase were investigated using the density functional theory （DFT） within the generalized gradient approximation （GGA）. The electronic density of states （DOS） obtained in this way accorded weU with the results of a recent study utilizing the full-potential linearized augmented plane wave （FLAPW） method. We also found that the density of d-states at the Fermi energy was low. The calculated equilibrium properties such as lattice constant, bulk modulus and its first derivative, and the elastic constants were in good agreement with experimental and theoretical results.

关键词： YCu, electronic band structure, density of states, elastic constants, bulk modulus, ab initio rare earths

Temperature-dependent dielectric properties of Au/Si_3N_4/n-Si (metal insulator semiconductor) structures

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Chinese Physics B 2013年第11期22卷 541-546页

作者： T.Ataseven A.Tataroglu Physics Department Faculty of Sciences Gazi University Teknikokullar

The dielectric properties of Au/Si3N4/n-Si （MIS） structures are studied using the admittance measurements （C–V and G/ω–V） each as a function of temperature in a range from 80 K to 400 K for two frequencies （100 kHz and 1 MHz）. Experimental results show that both the dielectric constant （ε’） and the dielectric loss （ε＂） increase with temperature increasing and decrease with frequency increasing. The measurements also show that the ac conductivity （σac） increases with temperature and frequency increasing. The lnσac versus 1000/T plot shows two linear regions with different slopes which correspond to low （120 K–240 K） and high （280 K–400 K） temperature ranges for the two frequencies. It is found that activation energy increases with frequency and temperature increasing.

关键词： Au/Si3N4/n-Si (metal-insulator-semiconductor) structure admittance measurements dielectricproperties ac conductivity

Quantification and spatial distribution of salicylic acid in film tablets using FT-Raman mapping with multivariate curve resolution

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Asian Journal of Pharmaceutical Sciences 2018年第2期13卷 155-162页

作者： Haslet Eksi-Kocak Sibel Ilbasmis Tamer Sebnem Yilmaz Merve Eryilmaz Ismail Hakkl Boyaci Ugur Tamer Department of Biomedical Engineering Faculty of Engineering Istanbul Aydin University Department of Pharmaceutical Technology Faculty of Pharmacy Gazi University Department of Analytical Chemistry Faculty of Pharmacy Gazi University Food Research Center Hacettepe University

In this study, we proposed a rapid and sensitive method for quantification and spatial distribution of salicylic acid in film tablets using FT-Raman spectroscopy with multivariate curve resolution(MCR). For this purpose, the constituents of film tablets were identified by using FT-Raman spectroscopy, and then eight different concentrations of salicylic acid tablets were visualized by Raman mapping. MCR was applied to mapping data to expose the active pharmaceutical ingredients in the presence of other excipients by monitoring distribution maps and combination of FT-Raman mapping with MCR enabled the determination of lower salicylic acid concentrations. In addition, the distribution of major excipient, lactose, was examined in the tablet form. A calibration curve was obtained by plotting the intensity of the Raman signal at 1635 cm^(-1) versus the concentration of salicylic acid and the correlation was found to be linear within the range of 0.5%–3.9% with a correlation coefficient of 0.99. The limit of detection for the technique was determined 0.35%. The ability of the technique to quantify salicylic acid in tablet test samples was also investigated.

关键词： Raman mapping Multivariate curve resolution FT-Raman spectroscopy Salicylic acid

Exploration of the Townsend regime by discharge light emission in a gas discharge device

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Chinese Physics B 2014年第1期23卷 289-296页

作者： Hilal Yucel Kurt hyucelkurt@*** []gazi university Faculty of Sciences Department of Physics 06500 Ankara Turkey

The Townsend discharge mechanism has been explored in a planar microelectronic gas discharge device （MGDD） with different applied voltages U and interelectrode distance d under various pressures in air. The anode and the cathode of the MGDD are formed by a transparent SnO2 covered glass and a GaAs semiconductor, respectively. In the experiments, the discharge is found to be unstable just below the breakdown voltage Ub, whereas the discharge passes through a homo- geneous stable Townsend mode beyond the breakdown voltage. The measurements are made by an electrical circuit and a CCD camera by recording the currents and light emission （LE） intensities. The intensity profiles, which are converted from the 3D light emission images along the semiconductor diameter, have been analysed for different system parameters. Dif- ferent instantaneous conductivity ~t regimes are found below and beyond the Townsend region. These regimes govern the current and spatio-temporal LE stabilities in the plasma system. It has been proven that the stable LE region increases up to 550 Torr as a function of pressure for small d. If the active area of the semiconductor becomes larger and the interlectrode distance d becomes smaller, the stable LE region stays nearly constant with pressure.

关键词： Townsend discharge breakdown microelectronic gas discharge device semiconductor cathode

Tensile fracture behavior of AA7075 alloy produced by thixocasting

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Transactions of Nonferrous Metals Society of China 2016年第5期26卷 1222-1231页

作者： Volkan KILICLI Neset AKAR Mehmet ERDOGAN Kadir KOCATEPE Department of Metallurgical and Materials Engineering Faculty of TechnologyGazi University

Tensile fracture behaviors of thixocast, artificially aged thixocast （thixocast＋T6） and as-extruded AA7075 alloys were investigated. The microstructural and fractographic observations were carried out using optical microscope （OM） and scanning electron microscope （SEM）. Experimental studies showed that as-extruded and thixocast＋T6 specimens exhibited considerably more excellent mechanical properties than as-thixocast AA7075 specimen. T6 artificial heat treatment with prolonged solution treatment significantly improved the tensile properties of the thixocast AA7075 alloy. The tensile properties of as-extruded and thixocast＋T6 specimens were close to each other. In as-thixocast specimen having remarkable micro-cracks, fracture was intergranular brittle type. The ductile fracture surfaces were observed in as-extruded and thixocast＋T6 specimens. In as-thixocast specimens, decohesion started between the eutectic-matrix interfaces and propagated through grains. Micro-void coalescence was the dominant form of fracture in thixocast＋T6 heat treated specimens. The micro-voids nucleation was initiated at the interface between the matrix and multinary eutectic structure.

关键词： AA7075 alloy semi-solid processing thixocasting tensile fracture behavior tensile properties