When studying and applying crystals of the middle category, it is necessary to take into account the manifestations of anisotropy of their properties, in particular, optical anisotropy. One of the manifestations of optical anisotropy is the rotation of the polarization plane (gyrotropy effect), which is observed in the direction of the optical axis of such crystals. The plane of polarization of light can rotate clockwise and counterclockwise. To determine the direction of rotation of the polarization plane, simple visual methods can be used based on studies of samples in converging polarized light – observations of conoscopic figures. In general, the type of conoscopic figures depends on the relative position of the polarizers, the wavelength of light in the system, the cut  of the single crystal perpendicular to which the light propagates, the thickness of the sample and the birefringence. The direction of rotation of the polarization plane can be determined by еру change of the type of conoscopic figure of a sample of a gyrotropic crystal cut perpendicular to the optical axis: change of the central spot color during the analyzer rotation; the extinction of the central spot when observing a conoscopic figure using light filters; the direction of movement of the rings in monochromatic light; observation of Airy patterns. According to the experience of working in our laboratory “Single crystals and Stocke on their Base”, the simplest, most operational and unambiguous visual method for determining the direction of rotation of the polarization plane is the observation of Airy figures. A conoscopic pattern in the form of Airy figures (a four-way spiral) occurs when observing in converging polarized light a combination of two superimposed samples of gyrotropic crystals cut perpendicular to the optical axis, rotating the plane of polarization of light in opposite directions. To use this method, a well-known sample of a gyrotropic crystal cut perpendicular to the optical axis is required.

Nanostructuring of thermoelectric materials (TEM) obtained by compacting nanodisperse powders is an effective way to increase their figure of merit by reducing phonon thermal conductivity. The optimal sizes of the structural elements of nanostructured TEM in the range of 10–100 nm, effectively scattering phonons with an average free path, which determine the maximum contribution to the heat transfer processes, have been established. Methods and modes of synthesis are presented, TEM based on: Bi₂Te₃; Sb₂Te₃; PbTe; GeTe and SiGe are obtained. A technology for producing nanodisperse TEM powders using a planetary ball mill has been developed. Optimal conditions for grinding TEM have been determined: the diameter of the grinding balls is 5 mm; the ratio of the mass of the balls and TEM is 10:1; the rotation speed of the planetary disk of the ball mill is 400 rpm; grinding time 50 min. Nanodisperse powders of the specified TEM are obtained. The phase composition, fine structure, and value of microdeformations of the obtained TEM nanodisperse powders were studied using transmission electron microscopy. It is established that at different times of powder grinding, the lattice parameters and, accordingly, the composition of TEM do not change. The values of microdeformations caused by mechanical action on the TEM change slightly with increasing powder grinding time. For all studied TEMs, except PbTe, the minimum dimensions of coherent scattering regions in powders are obtained at the level of 14–29 nm. For PbTe, these dimensions are much larger and amounted to 84–87 nm. 

The problem of growing high-resistance low-dislocation tubular silicon single crystals for non-planar manufacturing technologies of epitaxial p-n junctions and the production of new-generation power semiconductor devices is considered. The possibilities of Stepanov method for growing volumetric profiled crystalline products, the application of which is based on the use of shapers of various designs, are discussed. In particular, the shortcomings of shapers associated with the melt contamination by foreign particles and impurities are discussed. Therefore, the main attention is paid to the use of equipment that implements crystal growth from a melt without a shaper by Czochralski method. The processes of thermal mechanics are preliminary analyzed in relation to the existing and well-established process of growing polycrystalline highly dislocation silicon pipes of large diameter by Czochralski method for epitaxial reactors.
It is noted that the growth of tubular low-dislocation small diameter silicon single crystals requires a significant modernization of the standard hot zone, which in this work is implemented for “REDMET-10” Czochralski furnace. By means of computer simulation, thermal mechanical processes are calculated for such a modernized Czochralski furnace. The parameters of grown tubular silicon single crystals are characterized, and their manufacturing suitability for power semiconductor devices using nonplanar technology is assessed.

Simulation data have been presented on tellurium deep refinement process based on refinement technique developed by the Authors and implemented on the basis of analysis of the thermodynamical condition of the process unit using the FlowSimulation software from SolidWorks. The technique suggested herein has been implemented in a plant having a vertical air-tight reactor arranged inside a multi-zone thermal unit and providing for a combination of sequential refinement stages based on different techniques and integrated in a single process. The calculations are based on experimental data which have allowed one to determine the boundary conditions of the mathematical model using previous experience of work with the abovementioned software product. The temperature profiles have been calculated taking into account all the types of heat transfer in the system, the weight and dimensions of the system components and the physicochemical properties of refined tellurium, materials of reactor fittings and reactor media. The boundary conditions for the thermal calculations have been the temperature modes of process stages with specific known temperatures at local points of reactor fittings where temperature gages connected to a PID controller have been installed. During the simulation of specific process conditions for the refinement technique, process modes and design of equipment fittings components have been corrected. The Authors have developed and fabricated test models of the process and imitation equipment, and analysis of the thermal fields for the final model has shown good agreement with the mathematical model. Equipment upgrading and process parameter correction on the basis of the simulation results have allowed T-udo Grade tellurium to be refined to a 99.99992 wt.% purity by 30 main impurities with a product yield of at least 60% in the course of physical experiments.

In this work, the influence of deep levels formed at the SiON/AlGaN interface under the nitrogen plasma action during the deposition of a SiON film on the electrical parameters 
of SiON/AlGaN/GaN structures were studied. The concentration and mobility of free carriers in 2DEG and the capacitance parameters of the structures were measured. It has been experimentally established that short-term action of nitrogen plasma (25 and 50 sec.) does not change the concentration of free carriers in 2DEG, but leads to a decrease in their mobility. The value of the charge that can form at the SiON/AlGaN interface has been calculated. With the help of C–V measurements, it was experimentally shown how the charge in the SiON/AlGaN/GaN system changes during one measurement cycle at different voltage ranges. Based on the consideration of the energy band diagrams of the system, possible explanations for the charge redistribution processes in the analyzed system under certain actions are proposed.

The mechanism of formation of a film-forming medium during high-frequency deposition of strontium barium titan (Ba_xSr_1-xTiO₃) films in oxygen is considered. The study of the film-forming medium by mass spectrometry showed that when spraying Ba_xSr_1-xTiO₃ in oxygen plasma, the energy of oxygen ions 10^-17–10^-16 J is sufficient to transfer polyatomic molecules from the surface to the gas phase and insufficient to break the molecule into its constituent components both in the target substance and in the gas phase. The analysis of the mass spectra showed that in the voltage range 450–550 V, ionized particles with a mass number of 190–200, close to the molar mass of the compound Ba_0.2Sr_0.8TiO_3±x are registered in the gas phase. The grown polycrystalline films are chemically similar to the composition of the target Ba_0.8Sr_0.2TiO₃. With an increase in the bias voltage, ions with lower masses are recorded in the film-forming medium together with Ba_0.8Sr_0.2TiO_3±x, and the concentration of the number of ions with low mass increases with increasing bias voltage, and the formed polycrystalline films, along with Ba_0.8Sr_0.2TiO₃, contain compounds BaTiO₃, SrTiO₃, BaO and SrO. The dynamics of the formation of a film-forming medium during the deposition of Ba_0.8Sr_0.2TiO₃ films is shown. The parameters of the high-frequency discharge, conditions and modes necessary for reproducible growth of Ba_xSr_1-xTiO₃ films are established.

Theoretical calculations for the multilayer protection of a digital imaging detector (DDI) have been carried out. After analyzing the obtained attenuation coefficients of the calculated composite protection, its application for the formation of a neutron channel is proposed. The principle of operation of a multifunctional ionization chamber (MIC) for recording profiles of pulsed conditional spots from a neutron generator is considered. The principle of operation of the MIC chamber is based on the interaction of integrating electrodes and sensor cells. Sensor cells consist of 16 pads, the signals from which arrive in a pulsed mode synchronously with the incoming trigger signal. The 16 channel integrator board 1 board processes the input signals and sends them to the Deviation Detection Control Circuit (DDS). If the COOS circuit detects a deviation from the specified parameters, it immediately turns off the neutron generator (NG). A schematic diagram of a 16-channel charge-sensitive amplifier that exchanges information between the MIC camera and a computer is considered. Timing diagrams of the passage of signals are given on the example of one channel 1 board. The MIC chamber, together with the neutron beam channel and multilayer shielding, is designed for neutron therapy. Variants of composite multilayer protection of a medical channel based on a neutron source based on the NG-24 neutron generator are proposed. The channel design is built on the basis of Monte Carlo calculations on the example of selected protective materials - water, tivarobor and tungsten. A patent is considered, on the basis of which it is proposed to design a composite shadow protection of a neutron therapeutic channel. It is proposed to use the MIC chamber to control the dose profiles of neutron beams.

Director of the GPI RAS Corresponding Member of the Russian Academy of Sciences Sergey Garnov, Deputy Director for Research Doctor of Physical and Mathematical Sciences Vladimir Glushkov and Head of the Fianit Laboratory, Doctor of Technical Sciences Elena Lomonova By Decree of the President of the Russian Federation No. 290 of 18 May 2022 for their great contribution in the development of science and many years of conscientious work were awarded the Medal of the Order «For Merit to the Fatherland» II degree!