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Articles 31 - 60 of 74
Full-Text Articles in Physical Sciences and Mathematics
Electron Transport Mechanism In Gan/Algan Hemt Structures, Si̇bel Gökden
Electron Transport Mechanism In Gan/Algan Hemt Structures, Si̇bel Gökden
Turkish Journal of Physics
The electron transport mechanism in GaN/AlGaN HEMT (High Electron Mobility Transistors) structures grown with MBE on sapphire substrate was investigated by using the temperature dependence of the Hall coefficient, resistivity, carrier density and Hall mobility. Hall measurements were carried out using Van der Pauw geometry. From the LO-phonon-scattering-limited component of the mobility, we obtain LO phonon energy \hbar \omega \approx 90 meV and the momentum relaxation time of \tau_{m} \approx 4 fs. Also, from the temperature dependence of the 2D carrier density, we obtain the donor activation energy E_{a} \approx 29 meV.
Characterization Of In_{4}Te_{3} Single Crystals, M. Dongol, M. M. Nassary, M. K. Gerges, M. A. Sebag
Characterization Of In_{4}Te_{3} Single Crystals, M. Dongol, M. M. Nassary, M. K. Gerges, M. A. Sebag
Turkish Journal of Physics
Single crystals of In_{4}Te_{3} grown by modified Bridgman technique were characterized by measurement of the Hall coefficient, electrical conductivity and Seebeck coefficient, in the temperature range 200-500 K. The investigated sample was found to be of P-type conductivity.R_{H} at room temperature was 3.1 \times 10^{14} cm^{3}/coul and the carrier concentration was evaluated as 2.007 \times 10^{14} cm^{3}. Energy gap \Delta E_{g} and ionization energy \Delta E_{a} were estimated as 0.28 eV and 0.12 eV, respectively, and the diffusion coefficient, the diffusion length, the mean free time between collision and the effective mass of carriers were evaluated. The variation of the …
Variation In Thickness Of Copper Films Deposited At Various Distances And Angles Using The Thermionic Vacuum Arc, Tamer Akan, Naci̇ Ekem
Variation In Thickness Of Copper Films Deposited At Various Distances And Angles Using The Thermionic Vacuum Arc, Tamer Akan, Naci̇ Ekem
Turkish Journal of Physics
The thermionic vacuum arc (TVA) is a new technique for the deposition of thin metallic films. Copper depositions were made on glass substrates placed at various distances and angles with respect to the TVA source. By measuring the thickness of the film on each substrate, the variation in the thickness as a function of the distance and angle with respect to the TVA source is investigated.
Study Of The Structure And Some Physical Properties Of Sodium-Boro-Phosphate Glasses Containing Antimony And Iron Oxides, Karam Abdel-Aati̇ Ali, Ahmet Gamal El-Din Mostafa
Study Of The Structure And Some Physical Properties Of Sodium-Boro-Phosphate Glasses Containing Antimony And Iron Oxides, Karam Abdel-Aati̇ Ali, Ahmet Gamal El-Din Mostafa
Turkish Journal of Physics
Boro-phosphate glasses containing transition metal oxides are of special interest. Hence, some sodium-Boro-phosphate glasses containing iron and antimony oxides were prepared and investigated. The structural investigation indicated the presence of different borate groups as well as tetragonal phosphate units. Most of the iron cations were found to occupy the low spin Fe^{3 +} in the tetrahedral coordination state. It was observed that some antimony act as network former cations and some others act as bridges between any two adjacent polyhedra. At high antimony oxide content, the formation of some Sb-Fe bonds was also detected. The magnetic susceptibility measurements showed a …
Extragalactic Objects In Basle Fields, Selçuk Bi̇li̇r, Yüksel Karataş, Serap Ak
Extragalactic Objects In Basle Fields, Selçuk Bi̇li̇r, Yüksel Karataş, Serap Ak
Turkish Journal of Physics
We discriminated between the extragalactic objects (galaxies and quasars) and stars for Basle star fields, Plaut I, SA 54, and SA 82 by comparing Basle fields and APS POSS I finder charts. Their numbers are 187, 70, and 93 for Plaut I, SA 54, and SA 82, respectively. Most of these objects are apparently faint in V, and they cause an overestimated local luminosity function for absolutely faint magnitudes, M(V) > 5. This effect is more conspicious for the field Plaut I.
A Study Of Direct Two-Proton Transfer Reactions Using Optical Potential Model, A. K. A. R. Al-Farra
A Study Of Direct Two-Proton Transfer Reactions Using Optical Potential Model, A. K. A. R. Al-Farra
Turkish Journal of Physics
^{12}C, ^{26}Mg(^3He,n) reactions have been studied at high bombardment energy with evaluation of the differential cross sections to the ground and the first excited states evaluated in the framework of the exact finite-range Born approximation (DWBA) calculations using the optical model. With the constraint that bound-state interactions have a Thomas-Fermi spin orbit form, different formations of the bound-state wave functions are explored. The calculated angular distributions are found to be in a good agreement with the experimental data. The present DWBA predictions are normalized to give the best overall fits to the data. The extracted spectroscopic factors are reasonable.
Microwave Rotational Components Of The \Nu_9= 1 And \Nu _{10} = 2 Vibrational Modes Of ^{13}Ch_{3}Cch Molecule In The Range 16 -- 50 Ghz, Mohammad Al-Share, J. A. Roberts
Microwave Rotational Components Of The \Nu_9= 1 And \Nu _{10} = 2 Vibrational Modes Of ^{13}Ch_{3}Cch Molecule In The Range 16 -- 50 Ghz, Mohammad Al-Share, J. A. Roberts
Turkish Journal of Physics
Some rotational components have been measured in the ground, the \nu _9 = 1 and the \nu _{10} = 2 vibrational states for ^{13}CH_3CCH isotopic species in the frequency range 16--50 GHz. A set of rotational constants has been determined, which gives the best fit between the observed and the calculated frequencies, for each vibrational state. A Fermi resonance was found between these two states.
Studies On Some Lithium-Borate Glasses Containing Iron And Copper, G. A. Yahya
Studies On Some Lithium-Borate Glasses Containing Iron And Copper, G. A. Yahya
Turkish Journal of Physics
A lithium-borate-glass system containing iron and copper cations has been thoroughly investigated, in order to obtain information about the structural role of both the iron and copper in such glass hosts. The amorphous phase of the prepared glass samples was confirmed from their X-ray diffraction. From the infrared spectra it was concluded that the glass networks are highly deformed and boron appeared in both tri- and tetra-hedral coordination states as well as in some ring structure. As copper was introduced, replacing lithium, it acts as a network modifier only while the iron acts as network former (FeO_4). The molar magnetic …
Esr Studies Of A Quartz Single Crystal From The Menderes Massif-Turkey, Ülkü Ulusoy
Esr Studies Of A Quartz Single Crystal From The Menderes Massif-Turkey, Ülkü Ulusoy
Turkish Journal of Physics
In a recent work, quartz single crystal extracted from the pegmatitic vein in the Menderes Massif (Western Turkey) was investigated and the most recent geological events of the sample was dated using Al centers by ESR (electron spin resonance) techniques. The estimated age of 1.8 \pm 0.5 My agree with neither the previous age evaluated to be 12 My by using isotopic dating techniques nor the lifetimes of these centers in the sample. It was suggested that the thermal or geothermal stressing history of the metamorphic region must have changed the apparent ESR age several cycles in this period. The …
Photoelectrochemical Properties Of Cdse:Sb Thin Film Based Solar Cells: Influence Of Electrode Thickness, Elahipasha U. Masumdar, L. P. Deshmukh
Photoelectrochemical Properties Of Cdse:Sb Thin Film Based Solar Cells: Influence Of Electrode Thickness, Elahipasha U. Masumdar, L. P. Deshmukh
Turkish Journal of Physics
CdSe:Sb (0.1 mol%) thin films of varying thicknesses (423--1838 nm) have been deposited onto the glass and stainless steel substrates in an alkaline medium (pH = 10) using a solution growth technique. The photoelectrochemical activities of these films have been examined using CdSe:Sb (0.1 mol%)/0.25 M NaOH - 0.25M Na_2S- 0.25M S/graphite cell configuration. The films were characterized under illumination of 20 mW/cm^2} intensity to evaluate various cell parameters such as \eta, ff, R_s, R_{sh} etc. It is found that the efficiency \eta and fill factor ff increased from 0.24% to 0.45%, and 51% to 52.9%, respectively, with increase in …
Change Of Birefringence In Dye-Doped Nematic Liquid Crystals Under Laser Illumination, S. Eren San, Oğuz Köysal, Serhat Özder, F. Necati̇ Ecevi̇t
Change Of Birefringence In Dye-Doped Nematic Liquid Crystals Under Laser Illumination, S. Eren San, Oğuz Köysal, Serhat Özder, F. Necati̇ Ecevi̇t
Turkish Journal of Physics
Birefringence property of E7 nematic liquid crystal is investigated via voltage dependent transmittance spectrums. Measurements are performed at wavelength 632.8 nm, which is the absorbance peak of our sample including anthraquinone derivative Disperse Blue 14. Results of dye-doped samples are compared with those undoped for dark and laser illuminated cases. It was observed that birefringence is dependent on laser illumination for dye-doped samples, up to a threshold voltage after which it is constant.
Electrical, Optical, Structural And Morphological Properties Of Nis Films, Ferhunde Atay, Sali̇h Köse, Vi̇ldan Bi̇lgi̇n, İdri̇s Akyüz
Electrical, Optical, Structural And Morphological Properties Of Nis Films, Ferhunde Atay, Sali̇h Köse, Vi̇ldan Bi̇lgi̇n, İdri̇s Akyüz
Turkish Journal of Physics
The electrical, optical, structural and morphological properties of NiS films are less studied than other materials such as CdS, CdTe, ZnS, ZnO, CdO etc. Our aim in this work is to deposit NiS films, examine some of their physical properties and investigate their suitability for photovoltaic devices. NiS films were deposited onto glass substrates at a substrate temperature of 300 \pm 5 °C using the ultrasonic spray pyrolysis (USP) technique. The variations of temperature-dependent conductivity under the conditions of light and dark were investigated and it was seen that illumination reduces conductivity. The activation energy for the doped region and …
Null Membranes In Dyonic Black Hole Background, Alexandr Lelyakov, Sergey Nikolaevich Roshchupkin
Null Membranes In Dyonic Black Hole Background, Alexandr Lelyakov, Sergey Nikolaevich Roshchupkin
Turkish Journal of Physics
We consider null bosonic p-branes in curved spacetimes. The general solutions of the classical equations of motions and constraints for the null-membrane in four-dimensional dyonic black hole background are found.
Phase Measurements In Aharonov-Bohm Interferometers, Amnon Aharony, Ora Entin-Wohlman, Yoseph Imry
Phase Measurements In Aharonov-Bohm Interferometers, Amnon Aharony, Ora Entin-Wohlman, Yoseph Imry
Turkish Journal of Physics
In this paper we address measurements of the resonant quantum transmission amplitude t_{QD} = -i t_{QD} e^{i\alpha_{QD}} through a quantum dot (QD), as function of the plunger gate voltage V. Mesoscopic solid state Aharonov-Bohm interferometers (ABI) have been used to measure the ``intrinsic" phase, \alpha_{QD}, when the QD is placed on one of the paths. In a ``closed" interferometer, connected to two terminals, the electron current is conserved, and Onsager's relations require that the conductance G through the ABI is an even function of the magnetic flux \Phi = \hbar c\phi/e threading the ABI ring. Therefore, if one fits G …
Decoherence In Two Coupled Qubits, Kristian Rabenstein, Dmitri V. Averin
Decoherence In Two Coupled Qubits, Kristian Rabenstein, Dmitri V. Averin
Turkish Journal of Physics
We have developed quantitative description of quantum coherent oscillations in the system of two coupled qubits in the presence of weak decoherence that in general can be correlated between the two qubits. It is shown that in the experimentally realized scheme of excitation of the oscillations, their waveform is not very sensitive to the magnitude of decoherence correlations. Modification of this scheme into potentially useful probe of the degree of decoherence correlations at the two qubits is suggested.
Dephasing Of Entangled Electron-Hole Pairs In A Degenerate Electron Gas, J. L. Van Velsen, M. Kindermann, C. W. J. Beenakker
Dephasing Of Entangled Electron-Hole Pairs In A Degenerate Electron Gas, J. L. Van Velsen, M. Kindermann, C. W. J. Beenakker
Turkish Journal of Physics
A tunnel barrier in a degenerate electron gas was recently discovered as a source of entangled electron-hole pairs. Here, we investigate the loss of entanglement by dephasing. We calculate both the maximal violation E_{max} of the Bell inequality and the degree of entanglement (concurrence) C. If the initially maximally entangled electron-hole pair is in a Bell state, then the Bell inequality is violated for arbitrary strong dephasing. The same relation E_{max} = 2 \sqrt{1 + C^2} then holds as in the absence of dephasing. More generally, for a maximally entangled superposition of Bell states, the Bell inequality is satisfied for …
Decoherence In Ballistic Mesoscopic Interferometers, Georg Seelig, Sebastian Pilgram, Markus Büttiker
Decoherence In Ballistic Mesoscopic Interferometers, Georg Seelig, Sebastian Pilgram, Markus Büttiker
Turkish Journal of Physics
We provide a theoretical explanation for two recent experiments on decoherence of Aharonov-Bohm oscillations in two- and multi-terminal ballistic rings. We consider decoherence due to charge fluctuations and emphasize the role of charge exchange between the system and the reservoir or nearby gates. A time-dependent scattering matrix approach is shown to be a convenient tool for the discussion of decoherence in ballistic conductors.
Qce: A Simulator For Quantum Computer Hardware, Kristel Michielsen, Hans De Raedt
Qce: A Simulator For Quantum Computer Hardware, Kristel Michielsen, Hans De Raedt
Turkish Journal of Physics
The Quantum Computer Emulator (QCE) described in this paper consists of a simulator of a generic, general purpose quantum computer and a graphical user interface. The latter is used to control the simulator, to define the hardware of the quantum computer and to debug and execute quantum algorithms. QCE runs in a Windows 98/NT/2000/ME/XP environment. It can be used to validate designs of physically realizable quantum processors and as an interactive educational tool to learn about quantum computers and quantum algorithms. A detailed exposition is given of the implementation of the CNOT and the Toffoli gate, the quantum Fourier transform, …
Adiabatic Quantum Pumping Of Coherent Electrons, Ora Entin-Wohlman, Amnon Aharony, Vyacheslavs Kashcheyevs
Adiabatic Quantum Pumping Of Coherent Electrons, Ora Entin-Wohlman, Amnon Aharony, Vyacheslavs Kashcheyevs
Turkish Journal of Physics
We review recent theoretical calculations of charge transfer through mesoscopic devices in response to slowly-oscillating, spatially-confined, potentials. The discussion is restricted to non-interacting electrons, and emphasizes the role of quantum interference and resonant transmission in producing almost integer values (in units of the electronic charge e) of the charge transmitted per cycle, Q. The expression for the pumped charge is derived from a systematic expansion of the system scattering states in terms of the temporal derivatives of the instantaneous solutions. This yields the effect of the modulating potential on the Landauer formula for the conductance in response to a constant …
Quantum Computing With Electrons On Liquid Helium, İsmai̇l Karakurt
Quantum Computing With Electrons On Liquid Helium, İsmai̇l Karakurt
Turkish Journal of Physics
A quantum computer based on electrons floating over liquid helium is described. Each qubit is made of combinations of ground and first excited states of an electron trapped over micro-electrodes just below the helium surface. We describe mechanisms for preparing the initial state of the qubit, operations with the qubits, and a proposed readout. This system is, in principle, capable of \sim 10^4 operations in a decoherence time, the time in which the wave function collapses.
Persistent Currents In Mesoscopic Loops And Networks, Igor O. Kulik
Persistent Currents In Mesoscopic Loops And Networks, Igor O. Kulik
Turkish Journal of Physics
The paper describes persistent (also termed ``permanent", or ``non-decaying") currents in mesoscopic metallic and macromolecular rings, cylinders and networks. The current arises as a response of system to Aharonov-Bohm flux threading the conducting loop and does not require external voltage to support the current. Magnitude of the current is periodic function of magnetic flux with a period of normal-metal flux quantum \Phi_0 = hc/e. Spontaneous persistent currents arise in regular macromolecular structure without the Aharonov-Bohm flux provided the azimuthal periodicity of the ring is insured by strong coupling to periodic background (a ``substrate"), otherwise the system will undergo the Peierls …
Au Nanoparticle Clusters: A New System To Model Hopping Conduction, Ç. Kurdak, J. Kim, L. A. Farina, K. M. Lewis, X. Bai, M. P. Rowe, A. J. Matzger
Au Nanoparticle Clusters: A New System To Model Hopping Conduction, Ç. Kurdak, J. Kim, L. A. Farina, K. M. Lewis, X. Bai, M. P. Rowe, A. J. Matzger
Turkish Journal of Physics
We study electrical transport through self-assembled Au nanoparticle clusters which can be viewed as a new model system to study hopping transport. The physics of such systems is governed by two parameters: the charging energy and tunnel coupling between the particles. The charging energy is determined by the size of the nanoparticles. When the diameter of the nanoparticles is less than 4-5 nm the charging energy is large enough that Coulomb blockade effects were observed in electrical transport even at room temperature. The magnitude of the tunnel coupling between the particles was determined by the thiol coating used. To study …
Towards Quantum Communication With Electron Spins, D. S. Saraga, G. Burkard, J. C. Egues, H. A. Engel, P. Recher, Daniel Loss
Towards Quantum Communication With Electron Spins, D. S. Saraga, G. Burkard, J. C. Egues, H. A. Engel, P. Recher, Daniel Loss
Turkish Journal of Physics
We review our recent work towards quantum communication in a solid-state environment with qubits carried by electron spins. We propose three schemes to produce spin-entangled electrons, where the required separation of the partner electrons is achieved via Coulomb interaction. The non-product spin-states originate either from the Cooper pairs found in a superconductor, or in the ground state of a quantum dot with an even number of electrons. In a second stage, we show how spin-entanglement carried by a singlet can be detected in a beam-splitter geometry by an increased (bunching) or decreased (antibunching) noise signal. We also discuss how a …
First Principles Modeling Of Nanostructures, Serdar Öğüt
First Principles Modeling Of Nanostructures, Serdar Öğüt
Turkish Journal of Physics
Among the various theoretical tools for investigating microscopic material properties, ab initio (first principles) methods based on density functional theory and pseudopotentials have had a very good track record over the last two decades in terms of accuracy, reliability, and efficiency. The application of these methods to nanostructures to investigate their structural, electronic, and optical properties has, however, not been quite straightforward due to the large computational demand and new physics inherent in the nanometer and sub-nanometer size region. One particularly useful extension to overcome the computational demand imposed by localized nanostructures has been the introduction of methods based on …
Quantum State Generation And Entanglement Manipulation Using Linear Optics, Şahi̇n Kaya Özdemi̇r, Takashi Yamamoto, Masato Koashi, Nobuyuki Imoto
Quantum State Generation And Entanglement Manipulation Using Linear Optics, Şahi̇n Kaya Özdemi̇r, Takashi Yamamoto, Masato Koashi, Nobuyuki Imoto
Turkish Journal of Physics
Quantum information processing (QIP) requires unitary operations, measurements and synthesis, manipulation and characterization of arbitrary quantum states. Linear optics provides efficient tools for these purposes. In this review paper, we introduce the elements of linear optics toolbox, and briefly discuss some experimental and theoretical investigations using this toolbox. Our main focus will be the qubit state generation and entanglement extraction using linear optics toolbox.
Orbital Entanglement And Violation Of Bell Inequalities In The Presence Of Dephasing, P. Samuelsson, Eugene Sukhorukov, Markus Büttiker
Orbital Entanglement And Violation Of Bell Inequalities In The Presence Of Dephasing, P. Samuelsson, Eugene Sukhorukov, Markus Büttiker
Turkish Journal of Physics
We discuss orbital entanglement in mesoscopic conductors, focusing on the effect of dephasing. The entanglement is detected via violation of a Bell Inequality formulated in terms of zero-frequency current correlations. Following closely the recent work by Samuelsson, Sukhorukov and Büttiker [1], we investigate how the dephasing affects the possibility to violate the Bell Inequality and how system parameters can be adjusted for optimal violation.
Mesoscopic D-Wave Qubits: Can High-T_C Cuprates Play A Role In Quantum Computing?, Alexandre M. Zagoskin
Mesoscopic D-Wave Qubits: Can High-T_C Cuprates Play A Role In Quantum Computing?, Alexandre M. Zagoskin
Turkish Journal of Physics
Due to nontrivial orbital pairing symmetry, surfaces and interfaces of high-T_c superconductors support states which violate time-reversal (T-) symmetry. Such naturally degenerate states, useful as working states of a qubit, are standard for atomic or molecular-size qubit prototypes (e.g. based on nuclear spins), but exceptional for mesoscopic qubits. (In particular, they hold promise of a better scalability.) In these lectures I review the physics of T-breaking on surfaces and interfaces of high-T_c superconductors; then describe existing proposals for high-T_c based qubits and the current state of experiments; finally, I discuss the decoherence sources in the system, open questions, and future …
Mean Multiplicity Of Quark And Gluon Jets As A Function Of Opening Angle In E^{+}E^{-} \Rightarrow B\Overline{B} G Events, Ayda Beddall
Mean Multiplicity Of Quark And Gluon Jets As A Function Of Opening Angle In E^{+}E^{-} \Rightarrow B\Overline{B} G Events, Ayda Beddall
Turkish Journal of Physics
A comparison of the properties of quark and gluon jets has been madeby Monte Carlo simulation of the reaction Z \rightarrow b \overline{b} g. The jet energy is held fixed for every 5 GeV between 15--30 GeV energies and the mean multiplicity of b-quark and gluon jets are obtained as function of the angle between them. It is seen that the jet properties not only depend on the jet energies but also on the angle between the jets.
Preparation And Optimization Of High Quality Tin Films, Özlem Duyar, Cengi̇z Koçum, H. Zafer Durusoy
Preparation And Optimization Of High Quality Tin Films, Özlem Duyar, Cengi̇z Koçum, H. Zafer Durusoy
Turkish Journal of Physics
TiN thin films have been deposited by DC reactive magnetron sputtering method on glass substrates. The effects of the substrate temperature and the substrate bias voltage on the structural, optical and electrical properties of the films were studied by using XRD, STM, optical transmission and resistivity measurements. The bias voltage was varied in the 0 to 200 V range for two substrate temperatures, 100 °C and 300 °C. The results showed that the substrate bias voltage influenced the stoichiometry and structure of the films. The smoothest and least porous TiN films were prepared at about 160 V substrate bias voltage …
Admittance And Impedance Spectroscopy On Cu(In,Ga)Se_2 Solar Cells, A. Sertap Kavasoglu, Habi̇be Bayhan
Admittance And Impedance Spectroscopy On Cu(In,Ga)Se_2 Solar Cells, A. Sertap Kavasoglu, Habi̇be Bayhan
Turkish Journal of Physics
The present work reports some experimental results on the electrical properties of high efficiency ZnO/CdS/Cu(In,Ga)Se_2 heterojunction solar cells. Admittance spectroscopy has been employed for characterisation of the bulk and interface levels in the absorber Cu(In,Ga)Se_2 layer. The temperature dependent capacitance-frequency analysis indicated an emission from a shallow acceptor like defect level with an activation energy of about 75 meV. Information on the equivalent circuit model of the devices has been provided by the analysis of impedance measurements. The impedance data are presented in the Nyquist plot at several dc bias voltages at 300 K. The equivalent circuit model consisting of …