Open Access Published by De Gruyter Open Access

Volume 6 Issue 4

December 2008

Issue of Open Physics

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Journal Overview

Open Access September 27, 2008

Structural and optical properties of layers of pentacene formed by PLD method

Piotr Potera, Piotr Sagan, Ihor Virt, Marian Kuzma, Grzegorz Wisz, Ihor Rudyj, Marian Frugynski

Page range: 765-770

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Abstract

Organic films fabrication offers the possibility of producing electronic devices of low weight, mechanical flexibility and low cost. One suitable material for organic film fabrigation which is the subject of the great interest is pentacene, because it is characterized by the large carrier mobility (∼1 cm2/Vs). In this work, the growth of pentacene layers using pulse laser deposition (PLD) on different substrates (glass/ITO, Si) is described and various processing parameters are investigated. Two pulsed YAG:Nd3+ laser wavelengths were used for the ablation of the PLD target: the first harmonic at 1064 nm aGn:dNdth3+e second at 532 nm. The structure of the layers formed was examined using SEM and RHEED methods. The results were compared with results of optical spectroscopy studies. It will be shown that layers deposed using second harmonics have a higher quality than those for first harmonic. The other PLD parametersalso have a strong influence on the structure quality of layers.

Open Access September 27, 2008

On excited states of the Au3 cluster: an ab initio study

Alexander Rusakov, André Zaitsevskii

Page range: 771-774

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Abstract

Excited electronic states of the Au3 cluster are studied within the shape-consistent small-core relativistic pseudopotential model using many-body multipartitioning perturbation theory. Vertical transition energies and dipole moments are evaluated. For highly symmetric isomer, these theoretical results are in reasonable agreement with spectroscopic data from experiments.

Open Access September 27, 2008

In situ study of the 41Ar plume released from the Ignalina NPP

Rimvydas Jasiulionis, Linas Vyčinas, Andrej Rožkov

Page range: 775-780

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Abstract

The 41Ar gamma ray radiation was registered using the in situ method in the vicinity of the Ignalina nuclear power plant (NPP). The sum of gamma rays, that are reaching the HPGe detector, situated along the wind direction, from a number of plume segments and which are registered in the energy range of about 1.29 MeV, is calculated. An independent technological regime of the operating reactor method of the determination of the 41Ar emission rate from NPP stack is introduced.

Open Access September 27, 2008

The charge exchange reaction dp → (pp)n

Viktor Glagolev, Gabriela Martinská, Jan Mušinský, Nikolaj Piskunov, Jozef Urbán

Page range: 781-785

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Abstract

The ratio of the differential cross section of the charge exchange reaction of the deuteron to that of the nucleon, at small transferred momenta, has been discussed in order to estimate the spin-dependent part of the np → pn charge exchange amplitude.

Open Access September 27, 2008

Variable slip coefficient in binary lattice Boltzmann models

Lajos Szalmás

Page range: 786-791

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Abstract

We present a new method in order to obtain variable slip coefficient in binary lattice Boltzmann models to simulate gaseous flows. We present the Boundary layer theory. We study both the single-and multi-fluid BGK-type models as well. The boundary slip and the Knudsen layer are analyzed in detail. Benchmark simulations are carried out in order to compare the analytical derivation with the numerical results. Excellent agreement is found between the two analytical formalism and the numerical simulations.

Open Access September 27, 2008

On a current mechanism in Ta2O5 thin films

Povilas Pipinys, Alfonsas Rimeika

Page range: 792-796

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Abstract

Electrical conduction in the temperature range of 120–370 K has been studied in sandwiched structures of Al/Ta2O5/Si. The tantalum oxide films were prepared by evaporation of tantalum on a p-Si crystal substrate, followed by oxidation at a temperature of 600°C. The temperature-dependent current-voltage (I–V) characteristics are explained on the basis of a phonon-assisted tunnelling model. The same explanation is given for I–V data measured on Ta2O5 films by other investigators. From the comparison of experimental data with theory the density of states in the interface layer is derived and the electron-phonon interaction constant is assessed.

Open Access September 27, 2008

Electron irradiation effects in doped high temperature superconductors YBa2Cu3−x MxOy (M = Fe, Ni; x=0; x=0:01)

Aram Sahakyan, Sergei Nikoghosyan, Hrant Yeritsyan

Page range: 797-801

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Abstract

The influence of irradiation by electrons with an energy of 8 MeV, at dose intervals between 1013 and 2×1018el/cm2, on the properties of impurity doped, high-temperature superconductor YBa2Cu3−x MxOy (M = Fe, Ni; x=0; x=0:01) ceramics has been studied. It has been established that, as the irradiation dose is increased, the onset temperature of the transition to the superconducting state (T con), and the intergranular weak link coupling temperature between granules (T mJ), exhibit an oscillation around their initial values of approximately about 1–1.5 K. This oscillation indicates that the process of radiation defect formation in HTSC occurs in multiple stages. It was also found that the critical current (J c)decreases with an increase of the irradiation dose, and exhibits a local minimum at a dose of 8×1016el/cm2coinciding with minima for T con and T mJ at this dose. It was found that the introduction of Fe atoms to the ceramic decreases T mJ, while introducing Ni atoms decreases both T con and T mJ; it is suggested that this is a result of Ni substitution of Cu both in Cu2 plane sites and Cu1 chain sites. The introduction of Ni causes a large change in the intergranular critical current density, J c. A critical irradiation dose is obtained (2×1018)after which all HTSC parameters strongly decrease, i. e. the superconductivity of HTSC is destroyed.

Open Access September 27, 2008

A first-principles studies on TlX (X=P, As)

Yasemin Ciftci, Kemal Colakoglu, Engin Deligoz

Page range: 802-807

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Abstract

We present an ab initio study of the structural, electronic and thermodynamic properties of TlX(X=P,As). The plane-wave pseudopotential approach to the density-functional theory within the LDA and GGA approximations implemented in VASP (Viena Ab-initio Simulation Package) is used. The calculated lattice parameter, elastic constants, and band structures are compared with other available theoretical results, and good agreement is obtained. In addition, we have calculated the transition pressure (P t) from zinc-blende (ZB) to (rock-salt) NaCl structures, and have examined some thermodynamic properties.

Open Access September 27, 2008

Electronic properties of austenite and martensite Fe-9%Mn alloys

Ercan Uçgun, Hamza Ocak

Page range: 808-811

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Abstract

We calculate the electronic properties of austenite and martensite Fe-9%Mn alloys using the self consistent full-potential linearized-plane-wave method under the generalized gradient approximation full lattice relaxation. By minimizing total-energy, the lattice constants in their ground states were determined. We discuss the total energy dependence of the volume, and density of states (DOS).

Open Access September 27, 2008

The magnetic field dependence of the deformation potential materials in the square well confinement potential

Joung Sug, Su Lee, Jong Kim

Page range: 812-823

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Abstract

We study the optical Quantum Transition Line Shapes (QTLS) which show the absorption power and the Quantum Transition Line Widths (QTLW) of electron-deformation potential phonon interacting systems. In order to analyze the quantum transition, we compare the magnetic field dependencies of the QTLWand the QTLS on two transition processes, namely the intra-Landau level transition process and the inter-Landau level transition process. We apply the Quantum Transport theory (QTR) to the system in the confinement of electrons by square well confinement potential. We use the projected Liouville equation method with Equilibrium Average Projection Scheme (EAPS).

Open Access September 27, 2008

A symmetry based investigation of the band gap of SWCNTs

Mehdi Pakkhesal, Rahim Ghayour

Page range: 824-833

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Abstract

In this paper we use symmetry of Single Walled Carbon Nanotubes (SWCNTs) to generate some types of virtual sub-bands that are lower in number than the real sub-bands obtained through conventional-TB. It is shown that the virtual sub-bands maintain the value of band gap. In obtaining the sub bands, the interactions of the nearest and the second and third-nearest neighbors are taken into account. As the consequence of lower number of sub-bands, a significant reduction in computational effort has occurred and made the approach useful.

Open Access September 27, 2008

Onset of local ordering in some copper-based alloys: critical solute concentration vis-a-vis various solutionhardening parameters

Muhammad Butt, Mozina Noshi, Farooq Bashir

Page range: 834-842

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Abstract

The mode of planar distribution of solute atoms in Cu single crystals alloyed with 0.5 to 8.0 at.%Ge has been investigated via the temperature dependence of the critical resolved shear stress of these alloys. It is found that there exists a critical solute concentration c m ≈ 5 at.%Ge below which the distribution of solute atoms in the crystal is random, and above which some local ordering occurs. This together with such data available in the literature for Cu-Zn, Cu-Al and Cu-Mn alloys, i.e. c m ≈7 at. %Zn, 7 at.%Al and 1 at.%Mn, when examined as a function of the size-misfit factor δ = (1/b)(db/dc)of a given binary alloy system, shows that the value of c m strongly depends on δ; the smaller the magnitude of δ, the greater the value of c m and vice versa. Also, the value of c m is found to correlate well with the electron-to-atom ratio (e/a)of the Cu-Zn, Cu-Al, Cu-Ge and Cu-Mn alloys with the solute concentration c = c m. However, no systematic correlation exists between the critical solute concentration c m for the onset of local ordering and the modulus-mismatch parameter η = (1/G)(dG/dc).

Open Access September 27, 2008

Structural, dielectric, electrical and piezoelectric properties of Ba4SrRTi3V7O30 (R=Sm, Dy) ceramics

Priyadarshini Sahoo, Anuradha Panigrahi, Sunanda Patri, Ram Choudhary

Page range: 843-848

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Abstract

Polycrystalline samples of Ba4SrRTi3V7O30 (R=Sm and Dy), members of the tungsten-bronze family, were prepared using a high-temperature, solid-state reaction technique and studied their electrical properties (using complex impedance spectroscopy) in a wide range of temperature (31–500°C) and frequency (1 kHz-1 MHz). Preliminary structural (XRD) analyses of these compounds show the formation of single-phase, orthorhombic structures at room temperature. The scanning electron micrographs (SEM) provided information on the quality of the samples and uniform distribution of grains over the entire surface of the samples. Detailed studies of the dielectric properties suggest that they have undergone ferroelectric-paraelectric phase transition well above the room temperatures (i.e., 432 and 355°C for R= Sm and Dy, respectively, at frequency 100 kHz). Measurements of electrical conductivity (ac and dc) as a function of temperature suggest that the compounds have semiconducting properties much above the room temperature, with negative temperature coefficient of resistance (NTCR) behavior. The existence of ferroelectricity in these compounds was confirmed from a polarization study.

Open Access September 27, 2008

Structural and dielectric studies of lead-free ceramics: Na1/2Y1/2TiO3

Subrat Barik, Ram Choudhary, Prasanta Mahapatra

Page range: 849-852

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Abstract

The polycrystalline samples of Na1/2Y1/2TiO3 were prepared by the mixed-oxide method. A preliminary X-ray structural analysis was shown to exhibit the formation of a single-phase compound with an orthorhombic structure. Microstructural analysis by scanning electron microscopy (SEM) exhibits well defined grains distributed uniformly through out the sample suggesting the compactness and homogeneity of the sample. Detailed studies of dielectric properties of Na1/2Y1/2TiO3 in a wide frequency range (102–106 Hz) at different temperatures (31–500°C) show a dielectric anomaly at 105°C, which may be related to a ferroelectricparaelectric phase transition as suggested by hysteresis loop at room temperature. An ac conductivity (σ ac) of the material is mainly governed by the polaron hopping mechanism, which is also influenced by both frequency and temperature. The activation energy was obtained from the plot of temperature with a.c. conductivity.

Open Access September 27, 2008

Wide bandpass optical filters with TiO2 and Ta2O5

Muhammad Asghar, Muhammad Shoaib, Frank Placido, Shahzad Naseem

Page range: 853-863

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Abstract

Complex multilayer thin film filters for optical applications have been designed, prepared and characterized in this work. E-beam reactive evaporation technique has been used as a deposition process. In the first stage, optimized individual film layers of TiO2, Ta2O5, and SiO2 are deposited and characterized optically and structurally before the deposition of multilayered structures. The filter designs are based upon 33 layered SiO2/TiO2 and SiO2/Ta2O5 configurations on glass substrate. These designs are optimized to achieve wideband transmission in the visible spectrum. After deposition, the two filter configurations are characterized optically and structurally using spectrophotometery, atomic force microscopy (AFM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). SiO2/Ta2O5/glass filter has been found sensitive to deposition conditions since high absorption is observed in multilayered configuration for the as-deposited samples. Post-deposition annealing of the filter in the temperature range 150 to 250°C was also performed in order to study the effect of temperature on absorption and spectral characteristics of the filter. Comparison of the two filter configurations was also performed to analyze their suitability for optical applications. Adhesion of the two filters was found to be very good by means of tape-peel test.

Open Access September 27, 2008

On the Dirac eigenvalues as observables of the on-shell N = 2D = 4 Euclidean supergravity

Ion Vancea

Page range: 864-871

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Abstract

We generalize previous works on the Dirac eigenvalues as dynamical variables of Euclidean gravity and N =1 D = 4 supergravity to on-shell N = 2 D = 4 Euclidean supergravity. The covariant phase space of the theory is defined as the space of the solutions of the equations of motion modulo the on-shell gauge transformations. In this space we define the Poisson brackets and compute their value for the Dirac eigenvalues.

Open Access September 27, 2008

Left-handed chiral metamaterials

Cumali Sabah

Page range: 872-878

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Abstract

In this work, the concept of left-handed chiral metamaterials is analyzed by emphasizing their optical ability on the rotation of the plane of polarization of a wave. The possibilities of a negative phase velocity, negative and positive propagation constants, and basic electromagnetic properties of this novel medium are also presented. After the characterization of left-handed chiral metamaterial, we provide a reflection and transmission study for two planar boundaries of nonchiral-left-handed chiral metamaterial for normal angles of incidence. Some numerical results are also provided to validate the formulation found in the analysis and to show the role of the chirality in the propagation constants, phase velocities, reflection and transmission.

Open Access September 27, 2008

Application of asymptotic iteration method to the Khare-Mandal and its PT-symmetric QES partner potential

Okan Özer, Vedat Aslan

Page range: 879-883

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Abstract

We study the application of the asymptotic iteration method to the Khare-Mandal potential and its PT-symmetric partner. The eigenvalues and eigenfunctions for both potentials are obtained analytically. We have shown that although the quasi-exactly solvable energy eigenvalues of the Khare-Mandal potential are found to be in complex conjugate pairs for certain values of potential parameters, its PT-symmetric partner exhibits real energy eigenvalues in all cases.

Open Access September 27, 2008

Approximate analytical solutions of scattering states for Klein-Gordon equation with Hulthén potentials for nonzero angular momentum

Chang-Yuan Chen, Fa-Lin Lu, Dong-Sheng Sun

Page range: 884-890

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Abstract

In this paper, using the exponential function transformation approach along with an approximation for the centrifugal potential, the radial Klein-Gordon equation with the vector and scalar Hulthén potential is transformed to a hypergeometric differential equation. The approximate analytical solutions of t-waves scattering states are presented. The normalized wave functions expressed in terms of hypergeometric functions of scattering states on the “k/2π scale” and the calculation formula of phase shifts are given. The physical meaning of the approximate analytical solution is discussed.

Open Access September 27, 2008

A concise quantum mechanical treatment of the forced damped harmonic oscillator

Ti Li

Page range: 891-894

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Abstract

By selecting a right generalized coordinate X, which contains the general solutions of the classical motion equation of a forced damped harmonic oscillator, we obtain a simple Hamiltonian which does not contain time for the oscillator such that Schrödinger equation and its solutions can be directly written out in X representation. The wave functin in x representation are also given with the help of the eigenfunctions of the operator $$ \hat X $$ in x representation. The evolution of $$ \left\langle {\hat x} \right\rangle $$ is the same as in the classical mechanics, and the uncertainty in position is independent of an external influence; one part of energy mean is quantized and attenuated, and the other is equal to the classical energy.

Open Access September 27, 2008

An optical system with aberrations on diffraction integrals written in terms of a generalized ABCD matrix

Chaoying Zhao, Weihan Tan

Page range: 895-902

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Abstract

Abstract: In this paper, we consider the transformation of a ray beam as it passes through an optical system containing a glass plate with parallel surfaces inclined to the optical axis at the Brewster’s angle, by investigating the effects of the optical system on amplitude and phase distributions. By applying generalized matrix optics and diffraction integrals and considering the influence of a quarter of a wavelength of aberration on the transmitted amplitude and phase distributions at the focus of a de-collimating lens, we find that the central peak amplitude descends from 1.0 to 0.8 and the phase distortion is less than π/2. The general feature of the amplitude distribution shows an elongation along the y-axis perpendicular to the optical axis in the direction of tilt of the inclined plate, and conforms to the inclination direction of the glass plate.

Open Access September 27, 2008

Instability analysis of Gaussian beam propagation in a nonlinear refractive index medium

Chaoying Zhao, Weihan Tan

Page range: 903-911

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Abstract

In this paper, we use a thin filament two dimensional Gaussian beam to model the self-trapping filament. The instability of the propagation of a Gaussian beam through a nonlinear refractive index media is investigated, theoretically and numerically. Specifically, the small scale instability of the beam is examined. The numerical results show that the propagation of the two dimensional Gaussian beam presents one or more nonlinear focal points.

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Open Physics is a peer-reviewed, open access, electronic journal devoted to the publication of fundamental research results in all fields of physics. The journal provides the readers with free, instant, and permanent access to all content worldwide; and the authors with extensive promotion of published articles, long-time preservation, language-correction services, no space constraints and immediate publication.
Open Physics is listed inter alia by Clarivate Analytics (formerly Thomson Reuters) - Current Contents/Physical, Chemical and Earth Sciences, JCR and SCIE. Our standard policy requires each paper to be reviewed by at least two Referees and the peer-review process is single-blind.

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Special Issue on Predicting Patern Alterations in Nature
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Prof. Dr. Emile Franc Goufo, University of South Africa
Prof. Dr Seda İğret Araz, Siirt University, Turkey

The journal publishes research and review articles, rapid and short communications, comments and replies that cover the following areas of physical sciences:

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