Operating temperature of single-electron transistors

A modified approach is described to estimate the operating temperature of single-electron transistors which gives calculations in satisfactory agreement with the experimental data. Pis’ma Zh. Tekh. Fiz. 24, 16–19 (April 26, 1998)     

Intensity and phase of reflected radiation in a vanadium dioxide structure with surface plasmons

Results of theoretical calculations are presented for the angular dependences of the reflection coefficient and phase of reflected p-polarized radiation at wavelengths of 6328 Å and 11 500 Å in vanadium dioxide layered structures with surface plasmons. Results of calculations are presented for the two phases of the vanadium dioxide films — semiconducting and metallic. Pis’ma Zh. Tekh. Fiz. 23, 32–36 (July 12, 1997)     

Influence of the size effect on the permittivity of potassium tantalate forming part of a film capacitor

Calculations are made of the parameters of a phenomenological model of the permittivity of bulk and film samples of potassium tantalate as a function of the applied field and temperature. The correlation parameter needed to allow for the influence of the size effect is also calculated. Good agreement is obtained between the theoretical calculations and the experimental results. Pis’ma Zh. Tekh. Fiz. 24, 23–29 (November 12, 1998)     

Estimate of the potential relief (rippling) of a surface associated with adsorption of d-metal atoms on d-substrates

A cohesion approach developed previously by Davydov and Tikhonov to describe adsorption properties [Surf. Sci. 371, 157 (1997)] is used to calculate the ripple parameter Ω=E _dif/E _des (where E _dif and E _des are the activation energy of surface diffusion and the adsorption energy) for atoms of d-metals adsorbed on a W(110) surface. The results of the calculations show good agreement with the experimental data. Pis’ma Zh. Tekh. Fiz. 24, 70–74 (December 12, 1998)     

Boundary Conditions at the Bulk–Aerogel Interface of Superfluid 3He-B

We study the interface between bulk and aerogel impregnated with ³ He-B. The magnetic susceptibility at the interface determines a boundary condition for the texture, which can be parameterized by the orbital vector L. We use Ginzburg–Landau theory to calculate the boundary condition assuming homogeneous aerogel and a sharp interface. Recent NMR measurements give reason to conjecture that L tends to be parallel to interface. Our numerical calculations confirm this conjecture in the Ginzburg–Landau (GL) regime. However, the orienting energy is one order of magnitude smaller than at a solid wall, and therefore can easily be overshadowed by a nearby wall.     

Polarization recording of holograms in partially polarized recording light

A theoretical approach is considered for media whose scalar and anisotropic responses are of opposite sign. The nondiffracted beam, and the imaginary and real images formed by a polarization hologram are analyzed under these conditions. It is shown that the imaginary image has its polarization transformed compared with the object field while a pseudoscopic object field reconstructed in terms of polarization state and degree is formed in the real image. Pis’ma Zh. Tekh. Fiz. 23, 38–42 (February 12, 1997)     

Eigenvalues of damped structures: Vectoriteration in the original space of DOF

The equations of motion in structural dynamics as well as the corresponding eigenvalue problem are governed by 3 matrices for mass, damping and stiffness of order n which equals the number of degrees of freedom. High-performance eigenvalue-solvers are developed for only pairs A, B of matrices. Nevertheless, to benefit from these solvers, the original eigenvalue problem (λ² M+λD+K)x=0 is transformed into a linear eigenvalue representation with only two hypermatrices of double order 2n. Consequently the total numerical effort depends on this order 2n. This paper presents a vectoriteration process which actually works in the original space of order n and which needs no special actions like simultaneous iteration if complex conjugate eigenvalues λ, λˉ with identical norm have to be calculated. The theoretical foundation of this process still goes back to the pair of hypermatrices.     

Identification of singular interfaces with Δ<Emphasis Type="Bold">g</Emphasis>s and its basis of the O-lattice

This article identifies singular interfaces according to singularity in terms of structural defects, including dislocations and ledges. Defect singularities are defined by the elimination of one or more classes of defects, which must be present in the vicinal interfaces. In addition to the three commonly classified structural interfaces, a new type of interface—the CS-coherent interface—is introduced. Singularities in dislocation and ledge structures have been integrated in the study of orientation relationships (OR). The dislocation structures are determined through the O-lattice theory, originally proposed by Bollmann. The basic concepts of the O-lattice and related formulas from the original theory and extended studies are briefly reviewed. According to the theory, singular interfaces exhibiting singularity in the dislocation structures have been identified. An interface that is singular with respect to the interface orientation must be normal to at least one Δg, a vector connecting two reciprocal points from different lattices. An interface that is singular also with respect to the OR must obey one or more Δg parallelism rules. The selection of proper Δgs for different preferred states of interfaces are explained. Identification of singular interfaces with measurable Δgs provides a convenient and effective approach to the interpretation of the observed facets and ORs. The ambiguity about the selection of the deformation matrix (A) for the O-lattice calculation and the advantage of the O-lattice approach over the approach using the Frank–Bilby equation for the calculation of the interfacial dislocations are clarified. Limitations of the present approach and further study are discussed.     

Theory of multiple scattering in a fractal medium

An analysis is made of multiple scattering of particles whose ranges have a power-law distribution corresponding to a fractal medium. The small-angle approximation is used to derive an expression for the angular distribution of particles which have traversed a specific path. The results of numerical calculations are presented. Pis’ma Zh. Tekh. Fiz. 25, 34–40 (June 12, 1999)     

The Smoluchowski problem in polyatomic gases

A model kinetic equation is constructed which describes the behavior of molecular (polyatomic) gases in which the vibrational degrees of freedom are “frozen” and the rotational degrees of freedom are treated quasiclassically. An analytical solution is obtained for the Smoluchowski problem of the temperature jump and weak evaporation above a planar surface in a half space. Numerical calculations are carried out. Pis’ma Zh. Tekh. Fiz. 24, 85–89 (September 12, 1998)     

The Extended-focus,Auto-focus and Surface-profiling Techniques of Confocal Microscopy

Abstract

The extended focus and auto-focus techniques of confocal microscopy, which can be used to give greatly increased depth of field, are compared. These methods rely on the use of high numerical apertures, so that the paraxial approximation is found to give inaccurate theoretical image predictions. An improved approximation is discussed and compared with exact high-angle calculations. The confocal surface-profiling technique, which allows non-invasive investigation surface topography is also considered.     

Kinetic model of GaAs(100) growth from molecular beams

A kinetic model for the growth of GaAs(100) by molecular beam epitaxy is constructed. The elementary processes at the surface are analyzed, including chemisorption of atoms and molecules, incorporation of atoms into the crystal, decomposition of the crystal, and desorption of group-III atoms and group-V molecules in vacuum. The sticking coefficients and rate constants are obtained from a direct comparison with experimental data. The model can be used to determine the desorbed and reflected fluxes, the growth rate, and the coverage by groups III and V atoms as functions of the incident fluxes and temperature. The model can also be used to estimate the limits of validity of the thermodynamic approach and the minimum epitaxy temperature. The results of the calculations show good agreement with the experimental observations. Pis’ma Zh. Tekh. Fiz. 23, 64–71 (January 12, 1997)     

Use of lead as a neutral solvent for obtaining solid Ga1−x InxAsySb1−y solutions

The first results of an experimental investigation of the phase diagram of melting of the system Ga-In-As-Sb-Pb at temperatures 560 and 600 °C are presented. The solid solutions Ga_0.86In_0.14As_0.12Sb_0.88 at T=600 °C and Ga_0.81In_0.19As_0.16Sb_0.84 at T=560 °C, which are isoperiodic with the GaSb(100) substrate, are obtained from fluxed lead solutions. The experimental data are compared with theoretical calculations. Pis’ma Zh. Tekh. Fiz. 25, 77–81 (October 12, 1999)     

Nonlinear stage of instability evolution in a monostable active medium

A theoretical analysis is made of the nonlinear stage of instability evolution in a monostable active medium described by a “reaction-diffusion” type equation. The boundary of that region of the medium in which instability develops propagates at constant velocity. Group-theoretical analysis of the problem yields an analytic expression for the propagation velocity of this boundary. The results may be important for the analysis of instability evolution in a wide range of active media. Pis’ma Zh. Tekh. Fiz. 24, 10–15 (July 26, 1998)     

Intrinsic hardness of crystalline solids

The current status of various theoretical approaches to the “prediction” of material hardness has been reviewed. It is shown that the simple empirical correlation with the shear moduli generally provide very good estimates of the Vickers hardness. Semi-empirical models based solely on the strength of the chemical bonds, although performed as well, are theoretically incomplete. First-principles calculations of the ideal stress and shear strength is perhaps the most reliable and theoretically sound approach available to compare theoretical predictions with experiment.     

Optimization of Tetragonal KTa1−xNbxO3: Fe crystals as Storage Materials for Double-Exposure Holographic Interferometry

Abstract

Although the reconstruction of the Wigner function from generalized quasiprobability distributions that can be interpreted as smoothed Wigner functions poses no problem for theoretical calculations, there are, however, difficulties in the reconstruction when those distributions are gained from measurements.     

Application of Mel’nikov’s method for estimating the efficacy of external signals on complex nonlinear systems with strange attractors

Mel’nikov’s method is used as a criterion for determining the condition for the onset of stochastization in nonlinear dynamical systems with strange attractors. Analytical conditions for the onset of stochastization in Duffing systems and Lorenz systems are obtained, from which one can synthesize a control signal ensuring the required behavior of the system. A mathematical experiment is carried out which confirms the correctness of the theoretical analysis. Pis’ma Zh. Tekh. Fiz. 23, 40–45 (December 12, 1997)     

Theoretical Analysis of Metal-fibre Polarizer

Abstract

The theoretical analysis of a metal-fibre polarizer is presented. A specific form of electromagnetic fields of the polarizer is proposed. All important modes of the polarizer are found and their characteristics studied. Numerical calculations appear to be consistent with experimental results presented by other authors.     

Self-consistent model of a low-pressure rf capacitive discharge

A simple self-consistent model of a low-pressure rf capacitive discharge is formulated. Effects associated with stochastic heating of the electrons and the nonlocal nature of the electric field are taken into account. The relations obtained can be used for a qualitative analysis of the main features of these low-pressure discharges. The results of the numerical calculations show good agreement with available experimental data. Pis’ma Zh. Tekh. Fiz. 23, 39–45 (January 12, 1997)