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Current Tunnelling in MOS Devices with Al2O3/SiO2 Gate DielectricEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
With the continued scaling of the SiO2 thickness below 2 nm in CMOS devices, a large direct-tunnelling current flow between the gate electrode and silicon substrate is greatly impacting device performance. Therefore, higher dielectric constant materials are desirable for reducing the gate leakage while maintaining transistor performance for very thin dielectric layers. Despite its not very high dielectric constant (∼10), Al2O3 has emerged as one of the most promising high-k candidates in terms of its chemical and thermal stability as its high-barrier offset. In this paper, a theoretical study of the physical ...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Nanopinholes-Based Optical SuperlensEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A type of nanopinhole-based plasmonic structure is presented. It can realize superfocusing within micron-scale propagation distance with spatial resolution beyond diffraction limit. Cut-off wavelength effect is highlighted for understanding how periodicity distribution of the nanopinholes influences transmission and focusing through the structure. Redshift peak transmission occurs while the periodicity increases. In addition, focusing property of the plasmonic structures is analyzed for the monochromatic illumination with different incident wavelengths ranging from 400 nm to 750 nm. The easy fabricat...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

On the Spheroidal Semiseparation for Stokes FlowEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Many heat and mass transport problems involve particle-fluid systems, where the assumption of Stokes flow provides a very good approximation for representing small particles embedded within a viscous, incompressible fluid characterizing the steady, creeping flow. The present work is concerned with some interesting practical aspects of the theoretical analysis of Stokes flow in spheroidal domains. The stream function ψ, for axisymmetric Stokes flow, satisfies the well-known equation E4ψ=0. Despite the fact that in spherical coordinates this equation admits separable solutions, this property is not preserved wh...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Physics of Superpulses in Storage Ring Free-Electron LasersEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Contradictory to the widespread perception, storage ring free-electron lasers with substantial net gain can generate peak lasing power reaching GW levels in the so-called superpulse mode. This power level is sufficient for studies of nonlinear processes and efficient intracavity harmonic generation. This letter describes the physics of the superpulses and a phase-space refreshment in the electron beam responsible for this phenomenon. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Structural, Elastic, and Electronic Properties of ReB2: A First-Principles CalculationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The structural, elastic, and electronic properties of the hard material ReB2 have been investigated by means of density functional theory. The calculated equilibrium structural parameters of ReB2 are in agreement with the experimental results. Our result of bulk modulus shows that it is a low compressible material. Furthermore, the elastic anisotropy is discussed by investigating the elastic stiffness constants. The charge density and the electronic properties indicate that the covalent bonding of Re-B and B-B plays an important role in formation of a hard material. The good metallicity and hardness of ReB2 might serve a...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Quantum Transitions by Change of Parameters and in Noninertial MotionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
As it is well known, a quantum system depending on parameters exhibits the (geometric) Berry phase when parameters are varying in the adiabatic limit. A generalization of the Berry phase is given in the present paper for a nonadiabatic change of parameters, which leads to quantum transitions in the system. This generalization is applied to noninertial motions and it is shown that such motions may induce quantum transitions for a system in an external field governed by Schrodinger's equation. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Observation of Quantum Confinement Effects with Ultrashort Excitation in the Vicinity of Direct Critical Points in Silicon NanofilmsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report on the observation of quantum confinement effects and the influence of surface-related states due to the formation of nanograins on ultrashort relaxation near the direct critical points of silicon nanofilms following UV-excitation. Direct photoexcitation of the samples in the vicinity of the Γ critical points of the first Brillouin zone has been achieved using femtosecond pulses in the spectra range of 290–400 nm. Transient absorption measurements show a substantial enhancement of state filling with decreasing the film thickness down...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Molecular Field Calculation of Magnetization on NdRh2Ge2 Single CrystalEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Calculation of magnetization of the ternary single crystal compound NdRh2Ge2 has been carried out by using the wave-like molecular field model to explain the complex magnetic behavior. The field-induced magnetic structures having the propagation vectors, Q2=(0,0,39/40), Q3=(0,0,35/40), Q4=(0,0,31/40), and Q5=(0,0,0/40) (= the field-induced ferromagnetic phase) were proposed. Calculation on the basis of these structures and the antiferromagnetic phase with Q1=(0,0,1) well reproduces the experimental magnetization processes and H-T magnetic phase diagram. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Experimental Investigation of the Transition to Spatiotemporal Chaos with a System-Size Control ParameterEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Using a localized laser-heating method to allow the use of system size as a control parameter, we experimentally investigate, using liquid-crystal electroconvection with soft boundary conditions, the onset of spatial temporal chaos (STC) with increasing system size. We find that temporal periodicity is significantly quenched as the system size increases. The increase of the fourth moment (kurtosis) of the temporal Fourier transform provides a very useful quantitative measure of the loss of temporal periodicity (hence the onset of STC) as the pattern size increases, and also provides a simple means for determining a natural...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Differential Gain in InGaAsN/GaAs Double Quantum Well Structures by Numerical SimulationsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We performed numerical studies of differential gain in a coupled quantum well structures built from InGaAsN. Differential gain in In0.38Ga0.62As1_yNy/GaAs quantum well structures was determined and analyzed. A 10-band k_p Hamiltonian matrix was used in the calculations and solved self-consistently with Poisson's equation. The effect of Nitrogen composition and barrier thickness on differential gain has been determined. The influence of Nitrogen composition on differential gain is significant whereas barrier effects are modest. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

An Energy-Work Relationship Integration Scheme for Nonconservative Hamiltonian SystemsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This letter focuses on studying a new energy-work relationship numerical integration scheme of nonconservative Hamiltonian systems. The signal-stage, multistage, and parallel composition numerical integration schemes are presented for this system. The high-order energy-work relation scheme of the system is constructed by a parallel connection of n multistage scheme of order 2 which its order of accuracy is 2n. The connection, which is discrete analog of usual case, between the change of energy and work of nonconservative force is obtained for nonconservative Hamiltonian systems.This letter also shows that the more the stag...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Light Emitting Diodes of Inverse Spin ValvesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Light emitting diodes made out of inverse spin valves of a ferromagnetic half metal sandwiched between two nonmagnetic metals are proposed. Based on a giant spin-dependent chemical potential difference created under an external bias, the inverse spin valves are possible to emit light when electrons with the higher chemical potential flip their spins and become the electrons of the opposite spin with the lower chemical potential. The frequency of this type of light emitting diodes is tunable by the bias. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Storage of Energy in Disk-Shaped Laser MaterialsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Thin disk laser is analyzed, assuming that the heat is drained in the same direction, as the optical pulse, withdrawing the stored energy, comes. Amplified spontaneous emission, the background loss, and overheating are taken into account with simple model. The scaling laws of the basic parameters are deduced. For the case of fixed repetition rate, the upper bound of thickness is obtained. Key parameters are suggested. The key energy parameter is promoted as criterion for evaluation of different laser materials for the high energy, high mean power disk lasers. The maximum energy per active element is estimated. For the scal...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Synthesis and Characterization of Neodymium Oxide in Silica Matrix by Solgel Protocol MethodEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Formation of nanocrystalline rare earth was prepared by solgel route, using tetra-ethoxysilane and Nd (NO3)3 as precursor materials and HCl as a catalyst. The prepared samples were submitted to thermal treatments at temperature 500∘C (5 hours) and 800∘C (10 hours). Structural changes were investigated by XRD, FTIR spectroscopy, and SEM. At 800∘C (10 hours) resulted in the formation of cubic Nd2O3 nanocrystallites with average size ∼ 20 nm. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Optics of Chromites and Charge-Transfer TransitionsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Specific features of the charge-transfer (CT) states and O2p→Cr3d transitions in the octahedral (CrO6)9− complex are considered in the cluster approach. The reduced matrix elements of the electric-dipole transition operator are calculated on many-electron wave functions of the complex corresponding to the initial and final states of a CT transition. Modeling the optic spectrum of chromites has yielded a complicated CT band. The model spectrum is in satisfactory agreement with experimental data which demonstrates the limited validity of the generally accepted concept of a simple structure of CT spectra. (Sourc...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Ionic Conductivity and Phase Transition Behaviour in 4AgI-(1-x)PbI2-2xCuI SystemEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Samples of general formula 4AgI-(1-x)PbI2-2xCuI, x=0–0.4, have been prepared and investigated by XRD, DSC, and temperature-dependent conductivity studies. X-ray diffractograms showed the presence of binary system consisting of AgI and PbI2 in the sample x=0. Cu-substituted samples showed very similar diffractograms to that of the pure compound which indicates that no effect for the substitution on the nature of the binary system. DSC curves showed the presence of phase transition whose temperature increased with Cu+ ratio in the system. Ionic conductivity measurements confirmed the occurrence of the phase transitio...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Polarization Insensibility of Columnar Quantum Dot Structure Emitting at λ=1.55 μm: A Theoretical StudyEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Vertically stacked InAs/InP columnar quantum dots (CQDs) for polarization insensitive semiconductor amplifier in telecommunications applications are studied theoretically. An axial model is used to predict mechanical, electronic, and optical properties of these CQDs. A crossover from a dominant transverse electric (TE) optical ground state absorption to a dominant transverse magnetic (TM) absorption is predicted for a number of layers equal to about 9 in good agreement with the experiment. The weight of the light hole component of the valence band ground state increases as a function of the number of layers. The change of ...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Kleinberg Navigation on Anisotropic LatticesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We study the Kleinberg problem of navigation in small-world networks when the underlying lattice is stretched along a preferred direction. Extensive simulations confirm that maximally efficient navigation is attained when the length r of long-range links is taken from the distribution P(r)∼r−α, when the exponent α is equal to 2, the dimension of the underlying lattice, regardless of the amount of anisotropy, but only in the limit of infinite lattice size, L→∞. For finite size lattices we find an optimal α(L) that depends strongly on L. The convergence to α=2 as L!...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Comparison of the Solid Solution Properties of Mg-RE (Gd, Dy, Y) Alloys with Atomistic SimulationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Molecular dynamic simulations have been performed to study the solid solution mechanism of Mg100-xREx (RE=Gd,Dy,Y, x=0.5,1,2,3,4 at.%). The obtained results reveal that the additions of Gd, Dy and Y increase the lattice constants of Mg-RE alloys. Also the axis ratio c/a remains unchanged with increase in temperature, restraining the occurrence of nonbasal slip and twinning. Furthermore, it is confirmed that bulk modulus of Mg alloys can be increased remarkably by adding the Gd, Dy, Y, especially Gd, because the solid solubility of Gd in Mg decrease sharply with temperature in comparison with Dy and Y. Cons...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Evolving Networks with Enhanced Stability PropertiesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We use a search algorithm to identify networks with enhanced linear stability properties in this account. We then analyze these networks for topological regularities that explain the source of their stability/instability. Analysis of the structure of networks with enhanced stability properties reveals that these networks are characterized by a highly skewed degree distribution, very short path-length between nodes, little or no clustering, and dissasortativity. By contrast, networks with enhanced instability properties have a peaked degree distribution with a small variance, long path-lengths between nodes, a high degree o...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Effect of Sm Substitution on Structural, Dielectric, and Transport Properties of PZT CeramicsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The polycrystalline samples of Pb1−xSmx (Zr0.45Ti0.55)1−x/4O3 (PSZT) (where x = 0.00, 0.03, 0.06, and 0.09) were prepared by a high-temperature solid-state reaction technique. Preliminary X-ray structural analysis of the materials at room temperature has confirmed their formation in single-phase with tetragonal crystal structure. The temperature dependence of dielectric response of the samples at selected frequencies has exhibited their phase transition well above the room temperature. The variation of ac conductivity with temperature and the ...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Observation of Suprathermal Flux from SROSS-C2 Data at Low LatitudeEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The studies of suprathermal flux at equatorial latitude for low solar activity year of 1996 (from January to December) are reported. The retarding potential analyzer (RPA) data of Indian space research organization Stretched Rohini Satellite Series-C2 (SROSS-C2) are used. The suprathermal electron flux data are chosen in the height range of 475±50 km. Seasional, latitudinal, and height variations of suprathermal flux having energy range above 30 eV along with comparisons in latitudinal variation of small energy superathermal flux of 5 eV are also reported. The data are selected during the period...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

The Spatiotemporal Oscillations of Order Parameter for Isothermal Model of the Surface-Directed Spinodal Decomposition in Bounded Binary MixturesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The asymptotical behavior of order parameter in confined binary mixture is considered in one-dimensional geometry. The interaction between bulk and surface forces in the mixture is investigated. Its established conditions are when the bulk spinodal decomposition may be ignored and when the main role in the process of formation of the oscillating asymptotic periodic spatiotemporal structures plays the surface-directed spinodal decomposition which is modelled by nonlinear dynamical boundary conditions. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Evaluation of the Thickness in Nanolayers Using the Transfer Matrix Method for Modeling the Spectral ReflectivityEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The reflectivity spectra have been traditionally used to determine the thicknesses in semiconductor films. However, thicknesses of nanofilms are not easy to evaluate because the interference fringes are not visible in the transparent region. In this paper, we present a computed method based on the transfer matrix (TM) which is used to match the calculated and experimental room temperature reflectivity spectra of the ZnTe/GaAs films and to determine its thickness film values afterwards. The TM method needs only to know refraction indices and absorption coefficients as a function of wavelength for the film and the substrate....
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Maximise Global Gain in the Minority GameEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We find a simple, partially altruistic mechanism that can increase global gain for a community of selfish agents. The mechanism is implied in the phenomena found in the minority game. We apply the mechanism to a two-road traffic system to maximise traffic flow. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Reality of the Wigner Functions and QuantizationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Here we use the extended phase space formulation of quantum statistical mechanics proposed in an earlier work to define an extended lagrangian for Wigner's functions (WFs). The extended action defined by this lagrangian is a function of ordinary phase space variables. The reality condition of WFs is employed to quantize the extended action. The energy quantization is obtained as a direct consequence of the quantized action. The technique is applied to find the energy states of harmonic oscillator, particle in the box, and hydrogen atom as the illustrative examples. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

On the Appearance of a Cooper Minimum in the Photoionization Cross Sections of the Plasma-Embedded Li AtomEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The plasma screening effect is found to uncover a Cooper minimum in the photoionization cross sections from the ground state of the Li atom embedded in Debye plasma environment. The variation of the location of this minimum with Debye screening length is discussed and analyzed in terms of the instability of the ground state. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Waveguide Parameters of 19.8 kHz Signal Propagating over a Long PathEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The amplitude and phase of 19.8 kHz signal from navigational transmitter located in North West Cape, Australia, recorded at Suva, Fiji, have been utilized to determine the waveguide mode parameters. The propagation path is mixed over land and sea having Transmitter-Receiver Great Circle Path distance 6.7 Mm. The experimental values of the parameters were found to be consistent with the theoretical values calculated using the mode theory of VLF wave propagation in the waveguide. (Source: Research Letters in Physics)
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

On “GSI Oscillations” as Interference of Two Closely Spaced Ground Mass Eigenstates of H-Like Mother IonsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We analyse the hypothesis that the “GSI oscillations” of the K-shell electron capture decay (EC) rates of the H-like heavy ions are caused by quantum beats from a coherent state of two closely spaced ground mass-eigenstates |m′〉 and |m″〉 of decaying H-like heavy ions. We apply this mechanism to the calculation of the β+-decay rates of the H-like heavy ions and discuss the dynamics of the production of the H-like heavy ions with two closely spaced ground mass-eigenstates at GSI experiments. We show that such a mechanism cannot describe simultaneously the experimental data on bo...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

Structural and Magnetic Properties of Mn-Based Diluted Magnetic Semiconductors and AlloysEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Direct supercell approach calculations of the magnetic exchange interactions in Mn-doped ScN was carried out in the local spin density approximation by using the muffin-tin-orbital Green's function method. We found that magnetic interactions are long range interactions and affected by the randomness, band gap corrections, and carrier concentrations. Using total energy minimization approach we found that the global energy minimum of MnN is obtained for zinc-blende structure. If the compound is compressed by 6%, the energy minimum corresponds to the rock-salt structure in disagreement with the experimentally observed...
Source: Research Letters in Physics - October 28, 2009 Category: Physics Source Type: journals

On “GSI Oscillations” as Interference of Two Closely Spaced Ground Mass Eigenstates of H-Like Mother IonsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We analyse the hypothesis that the “GSI oscillations” of the K-shell electron capture decay (EC) rates of the H-like heavy ions are caused by quantum beats from a coherent state of two closely spaced ground mass-eigenstates |m′〉 and |m″〉 of decaying H-like heavy ions. We apply this mechanism to the calculation of the β+-decay rates of the H-like heavy ions and discuss the dynamics of the production of the H-like heavy ions with two closely spaced ground mass-eigenstates at GSI experiments. We show that such a mechanism cannot describe simultaneously the experimental data on bo...
Source: Research Letters in Physics - August 30, 2009 Category: Physics Source Type: journals

Waveguide Parameters of 19.8 kHz Signal Propagating over a Long PathEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The amplitude and phase of 19.8 kHz signal from navigational transmitter located in North West Cape, Australia, recorded at Suva, Fiji, have been utilized to determine the waveguide mode parameters. The propagation path is mixed over land and sea having Transmitter-Receiver Great Circle Path distance 6.7 Mm. The experimental values of the parameters were found to be consistent with the theoretical values calculated using the mode theory of VLF wave propagation in the waveguide. (Source: Research Letters in Physics)
Source: Research Letters in Physics - July 30, 2009 Category: Physics Source Type: journals

On the Appearance of a Cooper Minimum in the Photoionization Cross Sections of the Plasma-Embedded Li AtomEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The plasma screening effect is found to uncover a Cooper minimum in the photoionization cross sections from the ground state of the Li atom embedded in Debye plasma environment. The variation of the location of this minimum with Debye screening length is discussed and analyzed in terms of the instability of the ground state. (Source: Research Letters in Physics)
Source: Research Letters in Physics - July 14, 2009 Category: Physics Source Type: journals

Reduction of Time-Dependent Schrödinger Equations with Effective Mass to Stationary Schrödinger EquationsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We introduce a class of potentials for which the time-dependent Schrödinger equation with position-dependent (effective) mass allows reduction to a stationary Schrödinger equation. This reduction is done by a particular point canonical transformation which preserves L2-normalizability. (Source: Research Letters in Physics)
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

The Dyon Charge in Noncommutative Gauge TheoriesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We construct a dyon solution for the noncommutative version of the Yang-Mills-Higgs model with a ϑ-term. Extending the Noether method to the case of a noncommutative gauge theory, we analyze the effect of CP violation induced both by the ϑ-term and by noncommutativity proving that the Witten effect formula for the dyon charge remains the same as in ordinary space. (Source: Research Letters in Physics)
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Study of Magnesium Diboride Clusters Using Hybrid Density Functional TheoryEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Using hybrid density functional theory and a relatively large basis set, the lowest energy equilibrium structure, vibrational spectrum, and natural orbital analysis were obtained for magnesium diboride clusters [(MgB2)x for x=1,2, and 3]. For comparison, boron clusters [Bx for x=2,4, and 6] were also considered. The MgB2 and (MgB2)2 showed equilibrium structures with the boron atoms in arrangements similar to what was obtained for pure boron atoms, whereas, for (MgB2)3 a different arrangement of boron was obtained. From the population analysis, large electron density in the boron atoms formin...
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Computer Modeling of Displacement Cascades in Beryllium Irradiated with Intensive Neutron FluxEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Computer simulations of the radiation defects created in beryllium irradiated by fast neutrons (E>0.1 MeV) using the Geant4 and SRIM packages were carried out. The atom cascade displacements in Be at a neutron fluence of 1.6×1020 n/cm2 were determined to be 0.06 dpa and the helium concentration was calculated to be 168 appm. The concentration of L6i has been estimated to be 5% in comparison to the He concentration. Nanoscale calculations were done in 30×30×30 nm cube of fast neutron-irradiated Be. A correlation between the Be primary knock-on atom (PKA) en...
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Current Tunnelling in MOS Devices with Al2O3/SiO2 Gate DielectricEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
With the continued scaling of the SiO2 thickness below 2 nm in CMOS devices, a large direct-tunnelling current flow between the gate electrode and silicon substrate is greatly impacting device performance. Therefore, higher dielectric constant materials are desirable for reducing the gate leakage while maintaining transistor performance for very thin dielectric layers. Despite its not very high dielectric constant (∼10), Al2O3 has emerged as one of the most promising high-k candidates in terms of its chemical and thermal stability as its high-barrier offset. In this paper, a theoretical study of the physical ...
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Nanopinholes-Based Optical SuperlensEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A type of nanopinhole-based plasmonic structure is presented. It can realize superfocusing within micron-scale propagation distance with spatial resolution beyond diffraction limit. Cut-off wavelength effect is highlighted for understanding how periodicity distribution of the nanopinholes influences transmission and focusing through the structure. Redshift peak transmission occurs while the periodicity increases. In addition, focusing property of the plasmonic structures is analyzed for the monochromatic illumination with different incident wavelengths ranging from 400 nm to 750 nm. The easy fabricat...
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

On the Spheroidal Semiseparation for Stokes FlowEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Many heat and mass transport problems involve particle-fluid systems, where the assumption of Stokes flow provides a very good approximation for representing small particles embedded within a viscous, incompressible fluid characterizing the steady, creeping flow. The present work is concerned with some interesting practical aspects of the theoretical analysis of Stokes flow in spheroidal domains. The stream function ψ, for axisymmetric Stokes flow, satisfies the well-known equation E4ψ=0. Despite the fact that in spherical coordinates this equation admits separable solutions, this property is not preserved wh...
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Physics of Superpulses in Storage Ring Free-Electron LasersEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Contradictory to the widespread perception, storage ring free-electron lasers with substantial net gain can generate peak lasing power reaching GW levels in the so-called superpulse mode. This power level is sufficient for studies of nonlinear processes and efficient intracavity harmonic generation. This letter describes the physics of the superpulses and a phase-space refreshment in the electron beam responsible for this phenomenon. (Source: Research Letters in Physics)
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Structural, Elastic, and Electronic Properties of ReB2: A First-Principles CalculationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The structural, elastic, and electronic properties of the hard material ReB2 have been investigated by means of density functional theory. The calculated equilibrium structural parameters of ReB2 are in agreement with the experimental results. Our result of bulk modulus shows that it is a low compressible material. Furthermore, the elastic anisotropy is discussed by investigating the elastic stiffness constants. The charge density and the electronic properties indicate that the covalent bonding of Re-B and B-B plays an important role in formation of a hard material. The good metallicity and hardness of ReB2 might serve a...
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Quantum Transitions by Change of Parameters and in Noninertial MotionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
As it is well known, a quantum system depending on parameters exhibits the (geometric) Berry phase when parameters are varying in the adiabatic limit. A generalization of the Berry phase is given in the present paper for a nonadiabatic change of parameters, which leads to quantum transitions in the system. This generalization is applied to noninertial motions and it is shown that such motions may induce quantum transitions for a system in an external field governed by Schrodinger's equation. (Source: Research Letters in Physics)
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Observation of Quantum Confinement Effects with Ultrashort Excitation in the Vicinity of Direct Critical Points in Silicon NanofilmsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report on the observation of quantum confinement effects and the influence of surface-related states due to the formation of nanograins on ultrashort relaxation near the direct critical points of silicon nanofilms following UV-excitation. Direct photoexcitation of the samples in the vicinity of the Γ critical points of the first Brillouin zone has been achieved using femtosecond pulses in the spectra range of 290–400 nm. Transient absorption measurements show a substantial enhancement of state filling with decreasing the film thickness down...
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Molecular Field Calculation of Magnetization on NdRh2Ge2 Single CrystalEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Calculation of magnetization of the ternary single crystal compound NdRh2Ge2 has been carried out by using the wave-like molecular field model to explain the complex magnetic behavior. The field-induced magnetic structures having the propagation vectors, Q2=(0,0,39/40), Q3=(0,0,35/40), Q4=(0,0,31/40), and Q5=(0,0,0/40) (= the field-induced ferromagnetic phase) were proposed. Calculation on the basis of these structures and the antiferromagnetic phase with Q1=(0,0,1) well reproduces the experimental magnetization processes and H-T magnetic phase diagram. (Source: Research Letters in Physics)
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Experimental Investigation of the Transition to Spatiotemporal Chaos with a System-Size Control ParameterEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Using a localized laser-heating method to allow the use of system size as a control parameter, we experimentally investigate, using liquid-crystal electroconvection with soft boundary conditions, the onset of spatial temporal chaos (STC) with increasing system size. We find that temporal periodicity is significantly quenched as the system size increases. The increase of the fourth moment (kurtosis) of the temporal Fourier transform provides a very useful quantitative measure of the loss of temporal periodicity (hence the onset of STC) as the pattern size increases, and also provides a simple means for determining a natural...
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Differential Gain in InGaAsN/GaAs Double Quantum Well Structures by Numerical SimulationsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We performed numerical studies of differential gain in a coupled quantum well structures built from InGaAsN. Differential gain in In0.38Ga0.62As1_yNy/GaAs quantum well structures was determined and analyzed. A 10-band k_p Hamiltonian matrix was used in the calculations and solved self-consistently with Poisson's equation. The effect of Nitrogen composition and barrier thickness on differential gain has been determined. The influence of Nitrogen composition on differential gain is significant whereas barrier effects are modest. (Source: Research Letters in Physics)
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

An Energy-Work Relationship Integration Scheme for Nonconservative Hamiltonian SystemsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This letter focuses on studying a new energy-work relationship numerical integration scheme of nonconservative Hamiltonian systems. The signal-stage, multistage, and parallel composition numerical integration schemes are presented for this system. The high-order energy-work relation scheme of the system is constructed by a parallel connection of n multistage scheme of order 2 which its order of accuracy is 2n. The connection, which is discrete analog of usual case, between the change of energy and work of nonconservative force is obtained for nonconservative Hamiltonian systems.This letter also shows that the more the stag...
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals

Light Emitting Diodes of Inverse Spin ValvesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Light emitting diodes made out of inverse spin valves of a ferromagnetic half metal sandwiched between two nonmagnetic metals are proposed. Based on a giant spin-dependent chemical potential difference created under an external bias, the inverse spin valves are possible to emit light when electrons with the higher chemical potential flip their spins and become the electrons of the opposite spin with the lower chemical potential. The frequency of this type of light emitting diodes is tunable by the bias. (Source: Research Letters in Physics)
Source: Research Letters in Physics - June 10, 2009 Category: Physics Source Type: journals