卷 64, 编号 2 (2019)

Contact states at the interface of nonlinear media with anharmonicities of different signs are considered. A model that represents a boundary-value problem for the nonlinear Schrödinger equation is proposed. Several types of stationary states that depend on energy and describe local states in the vicinity of the interface, localization of nonlinear waves passing through the interface, and transformation of such waves are obtained for the system under study. Dispersion relations that make it possible to determine the energies of such states are derived. Explicit expressions for the energies of stationary states are obtained in the limiting cases.

Thresholds of explosive decomposition H_cr under irradiation using the first harmonic of a pulsed neodymium laser (14 ns) are experimentally determined for pentaerythritol tetranitrate (PETN) with aluminum nanoparticles (100 nm) at concentrations ranging from 0.05 to 1 wt %. Amplitudes of optoacoustic signals are measured versus concentrations of impurities in the sample at a fixed laser fluence. The experiments are performed in two regimes. In the first one, the irradiated surface of the sample is covered with a finite-weight glass plate that impedes the gas-dynamic unloading. In the second regime, an external pressure of no less than 10⁷ Pa is applied to the glass plate to prevent the gas-dynamic unloading. The interpretation of the experimental effects is proven by the results of theoretical simulation.

The absolute population of the B³Π_g state of molecular nitrogen is calculated from the intensity of electron-vibrational bands of the first positive system. The absolute population of the metastable A³Σ_u state of nitrogen molecules is calculated based on the solution of the balance equation. It is established that the population of the metastable state of molecular nitrogen increases with a decrease in the pressure and increase in the current intensity of the glow discharge. The results of determining the population of the A³Σ_u state of nitrogen molecules under conditions of simultaneous excitation of glow and vacuum arc discharges are presented.

The structural parameters ensuring high strength and low electrical resistance have been analyzed in Cu–Cr alloys exposed to severe plastic deformation (SPD) and aging. Specific resistance and strength characteristics have been modeled for a Cu–0.5 wt % Cr alloy with a nanostructure state caused by SPD. A comparison of modeling data with experimental values reveals the validity of the approach chosen for describing the above states. The formation of nanostructure states with high strength and low electrical resistance is shown to be due to simultaneous effects depending on the treatment conditions of materials.

Optimal geometrical and electrophysical parameters are calculated theoretically; the effective response of a solid-state hybrid “magnet–carbon—piezoelectric” sensor is studied experimentally. Experiments are performed under the action of an external magnetic field of low-frequency flexural resonances (from 1 to 230 Hz). Theoretical calculations have formed the basis for designing an experimental prototype of the instrument. The frequency dependence of the direct piezoelectric response to the applied small-signal varying magnetic action is constructed.

The concentration dependences of the resistivities and tensosensitivity factors of Ti_{1 –x}Cu_xInSe₂ alloys from TlInSe₂–CuInSe₂ system have been studied in concentration interval x = 0–0.1. It has been found that the concentration characteristics are linear in the range of solid solution existence (x = 0–0.025) and rapidly change outside this range.

Low-energy (E = 30 keV) Ag⁺ ions have been implanted into single-crystalline Si wafers (c-Si) with an implantation dose varying from 1.25 × 10¹⁵ to 1.5 × 10¹⁷ ions cm^–2 and an ion beam current density varying from 2 to 15 μA/cm². The surface morphology of implanted wafers has been examined using scanning electron microscopy, transmission electron microscopy, and atomic force microscopy, and their structure has been studied by means of reflection high-energy electron diffraction and elemental microanalysis. It has been shown that for minimal irradiation doses used in experiments, the surface layer of c-Si experiences amorphization. It has been found that when the implantation dose is in excess of the threshold value (~3.1 × 10¹⁵ ions cm^–2), Ag nanoparticles uniformly distributed over the Si surface arise in the irradiated Si layer. At a dose exceeding 10¹⁷ ions cm^–2, a porous Si structure is observed. In this case, the Ag nanoparticle size distribution becomes bimodal with coarse particles localized at the walls of Si pores.

Specific features of the structure formation in rapidly quenched high-cobalt alloy coatings formed by plasma sputtering have been investigated. The structural state of the investigated coatings has been identified by the X-ray diffraction technique. The sequence and kinetics of structural transformations occurring in the specified time-temperature heating regimes have been examined using differential thermal analysis. It has been established that heat generation and crystallization temperature depend on the conditions of formation of bulk amorphous coatings.

Application of heat-conducting coatings for cooling of high-power FETs based on heterostructures with arsenide–gallium substrate is theoretically analyzed. When the basic technology for manufacturing of transistors is employed in the absence of additional efforts aimed at a decrease in the thermal resistance of the substrate, the application of an additional thermal interface that represents a heat-conducting dielectric coating makes it possible to substantially decrease the overheating of the transistor channel. A several-fold decrease in such overheating can be reached using variations in the thickness of the coating and modification of the transistor structure and working regimes.

The surface morphology, crystal structures, and band-energy parameters have been studied for nanofilms and regularly arranged nanoscale Si phases with a thickness of 1–2 nm. The bandgap thickness of nanocrystalline Si phases with 2–3 single layers is found to be ~1.4 eV.

The Al₂O₃/Ge-p/Al₂O₃/Co system with an Al₂O₃ buffer layer deposited by ion-plasma sputtering has been experimentally investigated. The dependences of the magnetic properties of cobalt on the rate of its deposition by ion-plasma sputtering and rate of deposition of preceding layers have been established. It is shown that the technique used to obtain buffer layers can significantly reduce the surface roughness of the next layers. The obtained buffer layers can be used as artificial substrates for growing heterostructures with tunnel junctions.

An acousto-optic commutator of fiber-optic channels based on a ТеО₂ two-coordinate deflector has been proposed and realized. The commutator yields switching of optical radiation from a single output waveguide into a two-dimensional input matrix of waveguides, or vice versa, switching from any matrix waveguide into a single output one. The main interrelated parameters have been obtained. It has been established that the commutator has a short response time of 2–10 μs, yields up to several hundreds of switching channels, low insertion losses of 2–5 dB, and a considerable inter-channel isolation from –35 to –60 dB. Experiments were performed for the output matrix containing 19 waveguides. The channel multiplexing operating mode of this commutator has been demonstrated, which is simultaneous transmission of a signal from the output waveguide into a given number of waveguides of the input matrix.

Using the partial domain method, surface integral equations are obtained for slow-wave systems of double shifted combs taking dissipation on all metal surfaces into account. The case of aliquot comb periods is considered. The quadratic functionals are proposed as dispersion equations. A method to solve complex dispersion equations in the form of functionals for complex constants of propagation is proposed by means of their joint iterations with integral equations. The results of calculating the dispersion with allowance for dissipation in several structures considered are presented.

A technology of creation of annular silicon field emitters with bilayer metal–fullerene coating has been developed and their performance has been studied. It has been shown that annular emitters with a surface area of about 0.3 cm² provide a current up to 100–110 mA and stably operate under conditions of technical vacuum (~10^–7 Torr).

We have analyzed electron-stimulated desorption (ESD) of neutral sodium and potassium atoms on oxidized tungsten. We propose a model describing ESD of atoms from the oxidized tungsten surface.

Currently the most accurate measurements of neutron lifetime are being performed at the Petersburg Nuclear Physics Institute with ultracold neutrons (UCNs) stored in a gravitational trap. A modified setup with a large gravitational trap and cooling to 10–15 K is presented. The results of measurements of temperature dependence of UCN losses in collisions with walls, which were coated with a perfluorinated grease (Fomblin UT 18), at 300–77 K, are detailed. The probable heat inflow to the trap is estimated, and the feasibility of cooling to indicated temperatures in experiments with the modified setup is demonstrated.