Vol 42, No 10 (2016)

Molecular dynamic simulation of sputtering of bimetallic bipartite clusters bombarded by Ar₁ and Ar₁₃ particles is performed. The bombarded targets are 390-atom clusters consisting of two parts with equal number of atoms of the monocomponent fractions, Cu–Au and Ni–Al. The energy distributions of atoms in clusters and distributions of sputtered atoms with respect to the time of emission from clusters are obtained; these distributions testify to the increasing contribution of thermal evaporation of atoms into the sputtering yield of the metallic cluster with increasing size and energy of bombarding particles.

This work shows the possibility in principle of forming hydrocarbon structures in polyvinyl chloride films free of admixtures and polyvinyl chloride films modified with 5-mass % ferrocene via a radiation chemical transformation in the atmosphere with the use of an electron accelerator with a plasma cathode operating in the pulsed-periodic mode maximal electron energy no higher than 160 keV, pulse length of 40 μs, and current density of 5 mA/cm². According to the results of semiquantitative X-ray microanalysis, an irradiated polyvinyl chloride film free of admixtures contains 92 of carbon, 6 of oxygen, and 2 mass % of chlorine; the irradiated polyvinyl chloride is an amorphous carbon material. A possible mechanism of the phenomenon is discussed.

Results of experiments on the influence exerted by UV radiation on the height of the surface relief and on the diffraction efficiency of holographic diffraction gratings recorded on dichromated gelatin layers are reported. It is shown that the height of the surface relief substantially increases, which leads to a rise in the diffraction efficiency of the gratings to a value exceeding 25%.

Based on the results of numerical fluid dynamics simulation, an imitation parameter has been constructed which simulates the observed intensity of the laser plasma emission in a short-wave range. Within the computational model frame, a high-temperature perturbation is created in the jet that generates a strong shock wave. The resultant complicated target structure and its evolution lead to nonmonotonic time variations of the simulation parameter. This result agrees well with the experimentally measured behavior of emission from the laser plasma formed on the target perturbed by an additional laser prepulse.

The extraction efficiencies of edge luminescence from single-crystal silicon have been compared for three structures: textured without masking, untextured, and textured with masking by the technology of high-efficiency solar cells. The highest efficiency was obtained for the structure textured without masking. For this structure, the efficiency of power conversion at a wavelength of ~0.66 μm and power of 75 mW into edge PL power emerging from the semiconductor was η ≈ 0.8% under the nonradiative recombination conditions described by the exponential photoluminescence (PL) decay time constant of ~0.11 ms. The directivity diagrams of the edge PL were measured for the three structures under study.

The fundamental possibility of achieving temperature stability of laser emitters of 1.3-μm spectral range exhibiting a vertical microcavity and an active region based on InAs/InGaAs quantum dots (QDs) is investigated. It is demonstrated that using an undoped hybrid vertical optical microcavity formed by a lower undoped semiconductor and an upper distributed dielectric Bragg reflectors allows obtaining laser oscillation up to a temperature of ~100°C at nearly constant threshold optical pump power for an active region consisting of QD layers under optimal spectral mismatch between the position of maximum gain of the QD ground state and the resonance wavelength.

Cobalt nanotubes were fabricated by template synthesis in the pores of track membranes based on polyethylene terephthalate; modified by electron irradiation; and studied by scanning electronic microscopy, energy-dispersive analysis, and X-ray diffraction analysis. It was found that the resistivity of Co nanotubes dropped by 16.7 and 21.6% after electron irradiation with a dose of 50 and 100 kGy, respectively. It was demonstrated that the change in conductive properties is associated with the rearrangement of crystal structure after electron irradiation owing to the suppression of influence of the metastable β-Co phase and an increase in the degree of texturing in the <100> direction.

It is shown that the emission lines of N II nitrogen ions cannot contribute to the emission of other lines and be observed in the emission spectrum of plasma filaments, which are generated by femtosecond laser pulses with a peak intensity of ~50 TW/cm² in air. A simple procedure is described that allows evaluation of the ratio of the line intensities for the filamentation in air.

Terahertz electroluminescence caused by impurity-induced breakdown in lithium-doped silicon crystals is studied. The spectrum of the terahertz emission exhibits lines corresponding to intracenter electronic transitions between excited states of the impurity and sublevels of the ground state of the lithium donor. The spectrum also shows a background signal, which, apparently, is a manifestation of the effects due to heating at electric excitation.

Metamorphic InAs/InGaAs/InAlAs quantum wells with submonolayer InSb insertions have been grown for the first time by molecular beam epitaxy on GaAs (001) substrates using a graded InAlAs buffer layer with increasing In composition. The given nanoheterostructures demonstrate an intense photoluminescence at a wavelength of over of over 3 μm (80 K), which is shifted toward longer wavelengths as compared with that of the structures without InSb insertions.

A technique for detection of the theoretically predicted effect of transfer of a local disturbance from one phase boundary of a flat liquid zone to another during its thermomigration in a crystal is presented. The results of experimental studies of the peculiarities of an induced disturbance and its general effect on the stability of the flat zone are described. It is suggested to use the induced instability effect in silicon device structure engineering.

A highly sensitive laser polarization-optical technique was developed and applied to investigations of a ferrofluid, which was placed in a magnetic field. A colloid solution of magnetite in kerosene was used as a sample. It was shown that the magnetooptic response of this substance is reliably registered at a volume solid-phase content of down to ~10^–5. It was revealed that within a very wide range of changes in the solution concentration, a quadratic dependence of the observed birefringence value on the low-intensity field (up to several tens of oersted) is retained.