Volume 43, Nº 3 (2017)

The results of examination of characteristics of a CuBr laser operated in the double-pumping-pulse mode with a lasing pulse repetition rate of 50 Hz are presented. The potential to enhance the laser efficiency by choosing the optimum voltages of dissociation and excitation pulses and time delay values is discussed. It is confirmed that a more than twofold increase in the laser efficiency may be achieved through optimization and matched injection of the excitation-pulse energy into the active medium plasma. A laser efficiency as high as 2.6% (with respect to an excitation pulse) with an average power of 16 mW, an energy of 0.32 mJ, a halfamplitude laser pulse duration of 40 ns, and a time delay of 150 μs is demonstrated. The maximum average radiation power is 37 mW with an energy of 0.7 mJ and a laser efficiency of 0.7% at an energy density of 24 (2.7) mJ/cm³ of a dissociation (excitation) pumping pulse.

Data on the optical properties of a nanocomposite material constituted by gold nanoparticles covered with a thin film of amorphous hydrogenated silicon suboxide have been obtained for the first time. The thin film was deposited by gas-jet electron-beam plasma chemical-vapor deposition. As gold particles situated on the surface of quartz glass are covered with a thin a-SiO_x: H film, their plasmonic resonance peak is shifted to longer wavelengths. The calculations made in the study demonstrated a good agreement with the experiment.

Using a cryostat chamber developed for a spectrophotometer equipped with an integrating sphere, we have studied color centers (CCs) in photochromic titanium dioxide ceramics induced by radiation in the UV and visible spectral ranges. The channel of CC formation and annihilation during reductive-oxidation treatment is revealed, and the effect of thermoinduced growth of CC absorption has been found.

The central and noncentral harmonic force constants of the Keating model, proposed previously for describing elastic graphene constant, are obtained for 13 graphene-like IV–IV and III–V compounds. It is shown that the relative role of the noncentral forces decreases with an increase in the compound ionicity. For graphene, the anharmonic central-interaction constant is estimated and the dependences of the secondorder elastic constants on the two-dimensional pressure are calculated. Values of the photoelastic constants are determined.

Complex diagnostics (shadow shooting, smoke imaging, gas analysis) has shown the formation of flows at inleakage of a carbon-dioxide gas jet onto a porous barrier on its surface, inside it, and behind it, as well as the flow circulating between the nozzle and the barrier. The spatial distribution of CO₂ concentrations and the scheme of flows at jet interaction with a barrier are presented.

A technique is described for producing 2D-printing ink based on ultrasound exfoliated graphite (UEG). It has been established that the conductivity of a film obtained by microfiltration of such ink is 26.4 S/cm. Data on the morphology, composition, and IR spectra of UEG films are provided and compared with analogous data for reduced graphene-oxide films.

The dynamics of a spin-transfer nano-oscillator (STN) of the point-contact type under the action of a spin wave excited in the ferromagnetic layer by an external source is considered. It is shown that the STN can be synchronized by this external source, and the regions of synchronism capturing and holding in the space of parameters are established. Dependences of the spin-wave amplitude on parameters of the external signal are presented.

The interrelationship between the structure, phase composition, and transport characteristics of solid electrolytes based on ZrO₂ has been studied as dependent on the content of stabilizing Y₂O₃ additive. It is established that twin boundaries do not lead to the appearance of additional mechanism of ionic conductivity acceleration in ZrO₂–Y₂O₃ crystals. The maximum conductivity has been observed in ZrO₂–(8–10) mol % Y₂O₃ crystals containing a t” phase, in which oxygen atoms are displaced from high-symmetry positions characteristic of the cubic phase.

The optical-absorption spectra of InP/ZnS (core/shell) quantum dots have been studied in a broad temperature range of T = 6.5–296 K. Using the second-order derivative spectrophotometry technique, the energies of optical transitions at room temperature were found to be E₁ = 2.60 ± 0.02 eV (for the first peak of excitonic absorption in the InP core) and E₂ = 4.70 ± 0.02 eV (for processes in the ZnS shell). The experimental curve of E₁(T) has been approximated for the first time in the framework of a linear model and in terms of the Fan’s formula. It is established that the temperature dependence of E₁ is determined by the interaction of excitons and longitudinal acoustic phonons with hω = 15 meV.

A family of loading and control characteristics of a spin-transfer nano-oscillator (STNO) at various values of direct current have been constructed by integrating the Landau–Lifshitz–Gilbert–Slonczewski equation. The obtained characteristics are compared to approximated dependences calculated using truncated equations with respect to the first harmonic. An approximate expression is derived for the load resistance ensuring the maximum STNO output power.

We have experimentally studied the magnetoelectric (ME) effect in structures obtained by the electrolytic deposition of nickel onto gallium arsenide substrates. It is established that the use of a pre-deposited Ni–Au–Ge–Ni buffer sublayer significantly improves the adhesion of electroplated nickel to substrate. The resulting Ni–GaAs–Ni structures are featuring both linear and nonlinear ME effects with respect to the alternating magnetic field. Both these effects exhibit a resonance character, the resonance frequency of the nonlinear ME effect being two times lower than that for the linear effect.

The high-temperature superelasticity and temperature dependence of the yield stress of 14M and L1₀ martensite in [001]-oriented single crystals of Ni₅₄Fe₁₉Ga₂₇ (at %) in compression alloy have been studied. As the temperature increases, the sequence of stress-induced martensitic transformations (MTs) changes from L2₁–14M to L2₁–L1₀. The yield stress of L1₀ martensite weakly depends on the temperature and is 1.7 times lower than that of 14M martensite. The temperature interval of superelasticity in [001]-oriented single crystals of Ni₅₄Fe₁₉Ga₂₇ under compression is determined by the growth of critical stresses with increasing temperature, the coefficient of strain-hardening, and the yield stress of L1₀ martensite.