The paper studies the effect of ion-beam etching on the reflectivity characteristics of single-crystal silicon. The surface morphology formed during ion beam treatment was investigated and it was found that at normal incidence of Xe ions on the sample surface and low ion energies, a regular pit structure is formed with an increase in the amplitude of inhomogeneities in the spatial frequency range of 0.025–0.5 μm^-1, and at grazing incidence of Xe ions and high energies, a scaly topology is formed with an increase in the amplitude of inhomogeneities in the spatial frequency range of 0.025–10 μm^-1. Based on the study, a technique for forming a developed regular structure on the surface of a polished single-crystal silicon wafer with the (110) orientation using ion-beam etching is proposed. The technique consists in irradiating the surface of a single-crystal silicon sample with a wide quasi-parallel beam of monoenergetic Xe ions. It is shown that the treatment of monocrystalline silicon with a beam of accelerated Xe ions at an ion incidence angle of 70° and an ion energy of 1000 eV for only 30 min. forms a developed relief on the sample surface, reducing reflection and providing absorption of radiation with wavelengths in the wavelength range of 400–1000 nm by more than 90%. The technique provides a decrease in the reflection coefficient greater than that of black silicon prepared by standard technology at wavelengths of 532 and 793 nm, as well as in a wider range of incidence angles at wavelengths of 532, 633 and 793 nm, which in the future will allow the manufacture of solar power plants without expensive rotary supports and reduce their operating costs.

As a result of the analysis of the published results of studies on obtaining solid solutions of germanium – silicon, the possibilities of developing the technology of obtaining homogeneous crystals by methods of directional crystallization of melts are estimated.
Technological capabilities achieved in the last two or three decades make it possible to obtain Ge-Si single crystals with both variable and constant axial composition in the entire continuous series of solid solutions, and thereby meet the needs of scientific research. However, for the profitability of obtaining ingots of solid solutions on an industrial scale, complete automation of the technology of growing Ge–Si single crystals based on the methods of crucibleless zone melting and Czochralski is required. In the case of using these methods, the possibility of achieving high temperature gradients at the crystallization front allows for the growth of perfect single crystals at significantly higher rates of melt crystallization.
It was established that Ge_1-xSi_x solid solutions enriched with Ge have not been sufficiently studied and require fundamental research in connection with promising practical application. A design of a modified setup is proposed that allows for the synthesis of materials with a given composition and uniform distribution of the second component along the length of the ingot at alloying levels of less than 1%.
The thermal units developed during the study allowed for thermal conditions favorable for the formation of the Ge_1-xSi_x solid solution. The results of energy dispersive X-ray microanalysis indicate the incorporation of silicon into the polycrystalline germanium matrix and its distribution along the entire length of the crystal.

Growth of solid solutions of intermediate compositions LiNb_1-xTa_xO₃ crystals allows you to adjust the physical parameters of the material and obtain crystals with the required properties, which is why obtaining such crystals and studying their properties taking into account anisotropy is an urgent task. Crystals of solid solutions of lithium niobate tantalate LiNb_1-xTa_xO₃ of LiNb_0.88Ta_0.12O₃ and LiNb_0.93Ta_0.07O₃ compositions were grown in the work. Polished samples oriented in a standard installation were prepared from these crystals. The samples were subjected to monodomenization. The polarity of the piezoactive faces has been determined. By optical microscopy in transmitted light, patterns in the form of a sponge-like structure were observed on all samples of Z-cuts, patterns in the form of vertical regions parallel to the optical axis (Z-axis) were observed on samples of X- and Y-cuts. Taking into account anisotropy and polarity, measurements of the mechanical characteristics of the samples at a load of 25 gs were carried out: the microhardness of the samples according to Vickers HV calculated on the Mohs scale HM and the brittleness score Z_x. According to the obtained data, the parameters of the «viscosity» S according to the Palmquist method and the degree of ionic bonds are calculated. The effect of the Nb : Ta ratio on the microhardness of Z-cuts is ambiguous, this may be due to the significant heterogeneity of such samples. In the case of X-cut samples, the results of microhardness measurements are close and within the error limits of the method. In the case of Y-cuts, there is a significant difference in the values of microhardness and brittleness of Y«+» and Y«–» sections, while the microhardness of the sample with a higher Nb content is higher.

In this work the adsorption of the cobalt oxide on the surface of the “armchair” carbon nanotube (CNT) in three positions of the adsorption was investigated by quantum chemical modeling with methods of the density functional theory on the B3LYP/3-21G level. The values of the band gap of the pure CNT(6,6) and CNT(6,6)/Co₃O₄ composites with different adsorption positions were calculated and the mechanisms of its change were determined, the charge distribution in the obtained structures was analyzed. The conducted study permitted the establishment of the possibility of surface modification of CNT(6,6) with cobalt oxide in any of the considered adsorption positions, as evidenced by the observation of a process of chemical adsorption in all the given cases. Such modification leads to a decrease in the band gap, which is associated with an increase in the top of the valence band and a decrease in the bottom of the conduction band. The maximum decrease of the band gap is observed for the adsorption of cobalt oxide to a position where the cobalt atom of the cobalt oxide is located above the center of the CNT hexagon. The electron density shifts from the cobalt oxide to the surface of the CNT, while the cobalt atom of the cobalt oxide charges positively, and the carbon atoms nearby it charge negatively. The obtained results can be useful for the development of new nanoelectronics devices, gas sensors and biosensors.

A non-stationary one-dimensional physical and mathematical model of mass transfer of oxygen vacancies and trapped electrons in a self-consistent electric field is presented, this model allows to determine the influence of temperature on the electrophysical properties of metal oxide memristors.

Mathematical models of acoustic metamaterials based on classical and modified (with additional harmonic interaction between neighboring internal masses) one-dimensional infinite mass-in-mass chain are considered. Equations are obtained for the acoustic and optical branches of the dispersion relation, for the band gap width, and for the effective mass. Using the derived equations, the classical and modified mass-in-mass chains are modeled at different ratios of masses and spring stiffness. A qualitative analysis of an interesting special case ω_m = ω_M was performed, on the basis of which a formal generalization of the equations of relativistic quantum mechanics was obtained using the long-wave approximation.

The paper describes the problem of selecting electronic components in the inductive power supply system of implantable medical devices. It has been established that the use of components with low equivalent series resistance, as well as the use of capacitors with a temperature coefficient of capacitance of the NP0 type, allows reducing the heating of the inductive power transfer system with a class E power amplifier by more than 40%. A comparison of protective (conformal) coatings for reducing the heating of electronic components and increasing their resistance to the aggressive environment of the human body has been carried out. An experimental sample of the inductive power transfer system to implantable medical devices with a urethane conformal coating and a sealed polytetrafluoroethylene case has been developed and successfully tested on a laboratory animal.

The comparative analysis of the spectral-luminescent characteristics of upconversion luminescence in the visible spectral range for concentration series of single crystals and nanoparticles (1 - x)mol.%SrF₂–xmol.%ErF₃ (x = 1.6%, 3.2%, 5.3%, 7.4%, 11.5%, 13.6%, 15.7%) under excitation with radiation at a wavelength of 0.972 μm to the ⁴I_11/2 level of Er³⁺ ions has been conducted.

Interaction mechanisms in SrF₂–ErF₃ single crystals and nanoparticles were proposed based on the analysis of changes in the ratio of lines in the luminescence excitation spectra from the ⁴F_9/2 level under excitation to the ⁴F_7/2 level of Er³⁺ ions.

The model for the occurrence of upconversion luminescence in the visible spectral range in SrF₂–ErF₃ single crystals and nanoparticles under excitation with radiation at a wavelength of 0.972 μm to the ⁴I_11/2 level of Er³⁺ ions has been proposed.

On a medical accelerator “Prometheus“ at an energy of 200 MeV, a mixed secondary beam of delayed neutrons and a scanning high-intensity pencil beam of protons were designed to irradiate the tumor in flash therapy mode with a dose of 50–70 Gray. A neutron-forming target was used to produce fast neutrons and then delayed neutrons. The special design of the neutron-producing target allowed for several pulses of the accelerator to irradiate the outer surface of the tumor with scanning spots of protons and simultaneously irradiate the entire tumor area with delayed neutrons. Using the developed new composites for neutron protection, a mixed beam channel was constructed: delayed neutrons and scanning proton spots. The power profiles of the equivalent dose at the outlet of the channel for the neutron component of the channel were measured using an ionization pad chamber on a “warm liquid”. The pencil proton beam, scanning the entire outer surface of the tumor and sequentially changing the scanning depth, should destroy the superficial blood vessels on the outer surface of the tumor. The average radiation dose per session should be 50–70 Gray. A neutron beam simultaneously with protons during a flash therapy session irradiates the entire tumor area and has a combined value, working in the mode of the neutron capture dose-forming component of this treatment method, in the presence of the introduction of the desired sensitizer. It is proposed to enhance the effect of a proton beam scanning the tumor surface, due to additional dose generation from radio sensitizers based on nano-gold particles.