Vol 43, No 11 (2017)

Defects in a semiconductor structure of a photoelectric converter of solar energy based on a p–n junction with an antireflection film of porous silicon on the front surface have been studied by current deeplevel transient spectroscopy. An explanation of the influence of thickness of a porous-silicon film formed by electrochemical etching on the character of transformation of defects with deep levels and efficiency of solarenergy conversion is proposed.

A new method for the synthesis of porous crystalline tin-dioxide (SnO₂) layers from composites on the basis of multiwalled carbon nanotubes (MWCNTs) and nonstoichiometric amorphous tin oxide (MWCNT/SnO_x) is proposed. An MWCN/SnO_x composite layer produced by magnetron sputtering is annealed in air atmosphere at 500°C for 30 min. A homogeneous porous layer comprised of crystalline SnO₂ spherical particles with a size of about 0.1 μm is obtained as a result. In the process of annealing, nearly all the amount of carbon is removed in the form of gaseous oxides (only a small amount remains in the upper part of the porous SnO₂ layer). The structural defectiveness of nanotube walls, which increases because of the magnetron deposition of tin, plays a crucial role in the carbon oxidation and destruction of MWCNTs.

Some results of experimental studies of the vortex-core reconnection phenomenon in the flowthrough duct of a combined-flow turbine were presented. The studies were performed on a medium-scale hydrodynamic test bench, the design of which was maximally similar to real hydroturbines. Using high-speed recording in a regime with a 75% load in a suction-pipe diffuser, the reconnection of a precessing vortex-core with detachment of vortex rings was observed. Aperiodic pressure surges due to the reconnection of a vortex and the formation of vortex rings were experimentally detected.

The dependence of the crystallographic polarity of GaN epitaxial layers produced by nitrogen plasma-enhanced molecular-beam epitaxy on Si(111) substrates on the nitridation parameters and initial growth conditions has been studied. A rapid procedure for determining the polarity of GaN epitaxial layers was developed. It was found experimentally that the nitridation parameters of the silicon substrate have no effect on the polarity of a GaN layer. It was shown that the substrate temperature in the stage of nucleation of a GaN epitaxial layer is one of the factors determining its polarity.

The dielectric parameters of freshly produced freshwater ice in the microwave range are investigated. It is established that this kind of ice contains a noticeable amount of amorphous ice. Its production is associated with plastic deformation under mechanical stresses. An assessment of the dielectric-permeability change caused by amorphous ice in the state of a slowly flowing medium is given.

Fe–36Ni alloy is studied in states in which it is quenched, irradiated with electrons at 70 K, and deformed at 77 K. It is shown that similar structure-phase transformations occur in the investigated alloy during annealing at the temperature range of 70–570 K both after preliminary low-temperature electron irradiation and after preliminary low-temperature deformation. Migration of interstitial atoms (70–140 K) and vacancies (180–570 K), which induce phase transformations and are the results of atomic separation and ordering of zones with increased nickel content, is observed. Mechanisms of structure-phase changes under deformation and annealing are discussed.

Using a hypocycloidal electronic spectrometer, the interactions of low energy electrons (0–8.50 eV) with fructose molecules, namely, electron scattering and dissociative attachment, are studied. The results of these studies showed that the fragmentation of fructose molecules occurs effectively even at an electron energy close to zero. In the total electron-scattering cross section by molecules, resonance features (at energies ~3.10 and ~5.00 eV) were first observed near the formation thresholds of light ion fragments OH^– and H^–. The correlation of the features observed in the cross sections of electron scattering and dissociative attachment is analyzed.

It has been shown that such cathode spot characteristics as the average current per spot and its dependence on tangential magnetic-field induction B_t and the spot velocity and its dependence on B_t for two CuCr50/50 specimens with very different structures (nanocomposite and “solid-state sintered” composite) almost coincide if the surface of contacts has been totally remelted before measurements with the use of moderate arc currents in the process of conditioning.

The variation of electroacoustic-wave velocity in a vacuum gap of piezoelectric crystals under the action of homogeneous oscillatory displacement of one of the crystals along the gap boundary is considered.

The effect of epitaxial stresses on the excess-carrier dynamics and the terahertz radiation spectrum of the In_yGa_1–yAs films have been investigated by optical pump-probe and terahertz time-domain spectroscopy. It has been demonstrated that a In_yGa_1–yAs film with a higher mechanical stress has the shorter excesscarrier lifetime and broader terahertz radiation spectrum.

The changes of the current–voltage characteristics and the uncompensated donor-impurity concentration (N_d–N_a) in the base electrode of Schottky diodes and JBS diodes based on 4H-SiC have been studied upon their irradiation with 0.9-MeV electrons and 15-MeV protons. The carrier-removal rate was 0.07–0.15 cm^–1 under electron irradiation and 50–70 cm^–1 under proton irradiation. It was shown that the current–voltage characteristics of the devices under study remain rectifying at electron irradiation doses of up to ~1017 cm^–2. It was demonstrated that the radiation hardness of the SiC-based devices under study substantially exceeds that of silicon p–i–n diodes with similar breakdown voltages.

The possibility of using a powerful pulsed capillary discharge to produce quasi-stationary highspeed plasma flows with characteristic Mach numbers M = 3–10 and temperatures T = 3000–6000 K has been experimentally substantiated. In a rarefied gas atmosphere (p_∞ < 10 Torr), the transverse size of flow exceeds d < 3 cm and the duration of the working cycle can be brought to hundreds of milliseconds, which is of interest in problems of laboratory modeling of physical-chemical and gas-dynamic effects of interaction of bodies with hypersonic flows. Strong temperature nonequilibrium has been found (with the ratio between the vibrational and rotational temperatures reaching T_v/T_r = 3 and more) and anomalously low values of the effective adiabatic index, which indicates an intensive formation of polyatomic molecules and condensed particles in a carbon-containing plasma.

The value and sign of the electrostatic charge, potential, and magnetic-field intensity at the surface of a metallic body in its movement in the atmosphere and ionosphere were determined. Velocity and altitude and the motion were shown to be the main factors influencing the value and sign of mentioned functions.

A mathematical model of the response of a microchannel multiplier based on two microchannel plates in the chevron assembly has been considered. Analytical expressions relating the parameters of input and output signals have been obtained. The geometry of the chevron unit has been determined, and it has been optimized.