Analysis of current GaAs and related device market initiated in a number of earlier works has been continued. Binary semiconductor GaAs compound is a conventional MW electronics material. Until recently GaAs based HF ICs for mobile phones were among the most rapidly growing segments of GaAs market. However the GaAs market development trend is changing. Photonics and TeraHertz engineering are becoming the new world GaAs market drivers. This means that the current emphasize of GaAs single crystal technologies will shift toward vertical directional crystallization of “optoelectronic quality” crystals. In the medium and longer terms the world GaAs wafer and epitaxial structure markets will continue growing. In the shorter term we all will have to take into account COVID epidemic consequences. Still the GaAs market is closely related to Smartphone market novelties. Quite probably after a long growth period the GaAs market will keep on shrinking for the second consecutive year: GaAs production may decline by 11–12 % in 2020. Assuming that the epidemic will be somehow taken under control in 2021 the overall Smartphone production can probably be expected to grow starting from 2021.
Currently the Russian market of semiconductor compounds for photonics and electronic components (GaAs etc.) is but moderate and in predictable terms is not expected to achieve a level that is required for the emergence of a competitive domestic manufacturer, even though all importation replacement programs are accomplished. Meanwhile there is understanding that developing an advanced electronic components industry in Russia requires larger production of source materials.

The development of high energy physics and medicine has raised the necessity of heavy stintillating materials with a large total gamma quantum absorption cross-section, high quantum output and fast response. Cerium doped lutetium silicate Lu₂SiO₅ : Ce³⁺ (LSO) has high density, large effective atomic number and high conversion efficiency. In this work we have reported optical absorption spectroscopy and photoluminescence data for LSO single crystals grown using the modified Musatov method. The absorption spectra show the fundamental intrinsic absorption edge of Lu₂SiO₅ at ~200 nm and four extrinsic absorption bands of Ce³⁺ activator near 250—375 nm. The band gap is 6.19 to 6.29 eV depending on optical beam direction. We have confirmed that the extrinsic absorption bands correspond to optical transitions in Ce³⁺ activator ions localized in two crystallographically non-equivalent CeI and CeII positions. We have estimated that oscillator force for the optical transitions in Ce³⁺ ions. The photoluminescence spectra excited by 3.49 eV photon energy UV laser contain three bands: ~2.96 eV, ~3.13 eV (CeI) and ~2.70 eV (CeII). The energy structure of electron traps in LSO has been studied with thermally stimulated luminescence, the crystals being exposed to UV with different spectral and energy parameters. All the experimental thermally stimulated luminescence curves contain at least two peaks at 345 and 400 K with a 4 : 1 intensity ratio attributable to electron traps at 0.92—0.96 and1.12—1.18 eV. LSO exposure to high pressure mercury lamp radiation having the highest energy has for the first time showed the presence of traps at 0.88 eV. A model of the energy structure of LSO has been developed. The luminescence mechanism in the material is more complex than purely intracenter one. We show that high excitation energies may lead to ionization by the mechanism hv_a + Ce³⁺ = Ce⁴⁺ + e-. We have assumed that the storage of excitation energy involves not only Ce³⁺ activator but also the conduction band as well as trap states localized near the conduction band.

Artificial neural networks play an important role in the modern world. Their main field of application is the tasks of recognition and processing of images, speech, as well as robotics and unmanned systems. The use of neural networks is associated with high computational costs. In part, it was this fact that held back their progress, and only with the advent of high-performance computing systems did the active development of this area begin. Nevertheless, the issue of speeding up the work of neural network algorithms is still relevant. One of the promising directions is the creation of analog implementations of artificial neural networks, since analog calculations are performed orders of magnitude faster than digital ones. The memristor acts as the basic element on which such systems are built. A memristor is a resistance, the conductivity of which depends on the total charge passed through it. Combining them into a matrix (crossbar) allows one layer of artificial synapses to be implemented at the hardware level. Traditionally, the STDP method based on Hebb’s rule has been used as an analog learning method. In this work, we are modeling a two-layer fully connected network with one layer of synapses. The memristive effect can manifest itself in different substances (mainly in different oxides), so it is important to understand how the characteristics of memristors will affect the parameters of the neural network. Two oxides are considered: titanium oxide (TiO₂) and hafnium oxide (HfO₂). For each oxide, a parametric identification of the corresponding mathematical model is performed to best fit the experimental data. The neural network is tuned depending on the oxide used and the process of training it to recognize five patterns is simulated.

An urgent problem of radio engineering and radioelectronics nowadays is the synthesis of composite materials with preset parameters that can be used as electronics engineering materials. Of special interest are MW range wide-band electromagnetic radiation absorbers. Special attention is paid to materials on the basis of ferromagnetic metals that are capable of effectively absorbing and reflecting incident waves and having a clear nanostructure. Development of nanocapsulated metals will allow controlling the parameters of newly designed materials. This is achieved with the use of polymer matrices, e.g. pyrolyzed polyacrylonitrile (PPAN). This work is a theoretical study of a PPAN monolayer model containing pairs of transition metal atoms iron, nickel and cobalt which possess ferromagnetic properties, in Fe–Co, Ni–Co and Fe–Ni combinations, with silicon amorphizing admixture. We studied the geometrical structure of the metal composite systems which are modeled as PPAN molecular clusters the centers of which are voided of six matrix material atoms, the resultant defects (the so-called pores) being filled with pairs of the metal atoms being studied. The metal containing monolayer proved to be distorted in comparison with the initially planar PPAN monolayer. We plotted single-electron spectra of the composite nanosystems and characterized their band gaps. The presence of metal atoms reduces the band gap of a metal composite as compared with pure PPAN. We determined the charges of the metals and found electron density transfer from metal atoms to their adjacent PPAN monolayer atoms. We calculated the average bond energy of the test metal composite systems and proved them to be stable. The studies involved the use of the density functional theory (DFT) method with the B3LYP functional and the 6-31G(d) basis.

Modification of the polished {111} surface of single-crystal germanium (n-type, resistivity 47 Ohm · cm), exposed to radiation of a focused frequency-pulse nanosecond ultraviolet Nd : YaG laser, was studied by optical profilometry, scanning electron and probe microscopy. It was revealed, that the threshold of plasma formation with generation of a crater on the surface, occurs at an energy density of E ~ 1.2—1.3 J/cm². When the sample was stationary, at E ~ 0.1 J/cm² irreversible damage to the surface occurred. When scanning the surface with radiation at E ~ 0.50—1.15 J/cm², in the absence of noticeable traces of crater formation, the generation of etching pits with a regular triangular shape was observed, the concentration of which was (3—5) · 10⁵ cm². The figures resemble dislocation-etching pits, usually obtained by selective chemical etching.
Dislocations were detected by ablation because of exposure to laser radiation. The centers of ablation nucleation are dislocations that come to the crystal surface. The transverse dimension of etching pits was ~ 5—10 µm and their overlap led to an alternating picture of trihedral pyramids, formed by the {111} planes. The presented images show the rounded edges and tops of the pyramids and the height of the profile of the figures ~ 1—2 μm. The linear dimensions of the pits testify a rapid flow of the process. Based on the total time of exposure to radiation on the surface ~ 200 ns, the rate of formation of flat faces in the pits equal to ~ 0.1—0.3 m/s, which is several orders of magnitude higher, than the rate of formation of the same faces during crystal growth was established. The depth of the surface layer, in which the structure was formed, was ~ 15 μm.

The paper presents the results of a study of the luminescent properties of calcium gallate activated by trivalent rare earth ions Yb³⁺ and Er³⁺. IR luminescence spectra of samples with a single activator Ca_1‑хYb_xGa₂O₄,Ca_1‑хEr_xGa₂O₄ were studied when excited by radiation sources with a wavelength of 940 and 790 nm, respectively. The dependence of the luminescence intensity of samples on the concentration of rare earth ions is obtained. When the two-activator composition of Ca_1‑х‑yYb_xEr_yGa₂O₄ is excited by a semiconductor laser diode with a wavelength of 940 nm, IR luminescence is registered in the regions of 980-1100 nm and 1450-1670 nm. The radiation in these bands corresponds to electronic transitions in Yb³⁺ and Er³⁺ ions, respectively. For a luminescence band with a maximum at a wavelength of 1540 nm, the excitation spectra were measured, the maximum intensity is at the wavelengths: 930, 941, 970, 980 nm. The dependence of the IR luminescence intensity of a solid solution of Ca_1‑х‑yYb_xEr_yGa₂O₄ on the concentration of Er³⁺ ions was studied. With an increase in the concentration of Er³⁺ ions in the luminescence spectra, there is a redistribution in the intensity of the bands belonging to Yb³⁺ and Er³⁺ ions, which indicates the presence of energy transfer processes between these ions. The kinetics of IR luminescence attenuation was studied for series with one and two activators: Ca_1‑хYb_xGa₂O₄,Ca_1‑хEr_xGa₂O₄, Ca_1‑х‑yYb_xEr_yGa₂O₄. It is established that the luminescence attenuation occurs mainly according to the exponential law, which indicates the predominance of the intracenter luminescence mechanism in the studied structures. Based on the analysis of the excitation and luminescence spectra of experimental samples, conclusions are made about the interaction of Yb³⁺ and Er³⁺ activator ions in the crystal lattice of calcium gallate.

It is known that high purity aluminum with a minimum content of impurities is widely used in electronic technology for the manufacture of conductive paths in integrated circuits. Hence the development of new compositions of alloys based on such a metal is a very urgent task. One of the promising alloys based on such a metal is alloy AK1M2 (Al + 1 % Si + 2 % Cu). This alloy was accepted by us as a model alloy and subjected to modification by alkaline earth metals.
Heat capacity is the most important characteristic of substances and by its variation with temperature one can determine the type of phase transformation, the Debye temperature, the energy of formation of vacancies, the coefficient of electronic heat capacity, and other properties. In the present work, the heat capacity of the AK1M2 alloy with alkaline earth metals was determined in the “cooling” mode from the known heat capacity of a reference sample from copper. For which, by processing the curves of the cooling rate of samples from the alloy AK1M2 with alkaline earth metals and the standard, polynomials were obtained which describe their cooling rates. Further, by experimentally found values of the cooling rates of the standard and samples from alloys, knowing their masses, the polynomials of the temperature dependence of the heat capacity of the alloys and the standard were established, which are described by a four-term equation. Using the integrals of the specific heat, the models of temperature dependence of the change in enthalpy, entropy and Gibbs energy were established.
The dependences obtained show that with an increase in temperature, the heat capacity, enthalpy, and entropy of alloys increase, and the values of Gibbs energy decrease. At the same time, additives of alkaline earth metals do not significantly reduce the heat capacity, enthalpy and entropy of the original alloy AK1M2 and increase the value of Gibbs energy. During the transition from alloys with calcium with barium, the heat capacity of the alloys decreases, which correlates with the heat capacity of pure alkaline earth metals within the subgroup.

The article describes the proposed new multifunctional ionization chamber (MIC) designed to measure dose profiles when the medical accelerator Prometheus is operating in the scanning “pencil beam” mode. A digital image acquisition detector (DIDE) with a tissue-equivalent water phantom is used to calibrate the accelerator before a radiation therapy session. The application of the CPPI on the beam of a proton accelerator operating in the mode of beam splitting into spots with a scanning beam is considered. The CDPI detector allows for a few accelerator pulses in on-line mode to see how the energy release of each spot is distributed over the area of the irradiated target, which is the actual calibration of the accelerator before the proton therapy session. During the proton therapy session, it is planned to install the MIC directly in front of the patient. The MIC chamber contains two ionization chambers operating simultaneously — a pad chamber (PC) operating on gas or “warm liquid” and a strip ionization chamber operating only on gas (SC). At the accelerator Prometheus it is proposed to use a MIC, which will be used in the mode of operation by the method of active scanning with a “pencil” proton beam. The use of the MIC operation is intended to control the density of the beam intensity during the irradiation of the “target” in the patient during the proton therapy session. In case of violation of the planned operating mode of the accelerator and the beam goes beyond the parameters preset before the session, the deviation detection control system (SDMS) will turn off the accelerator. The device of the readout electronics (SE) of the MIC and SKOO cameras is described. This proposed detector, including the MIC and SKOO camera and the reading electronics serving it, will improve the quality of the therapeutic beam supply, due to the accurate determination of the absorbed dose density supplied by the scanning beam to each spot of the irradiated target, and therefore the generated high dose distribution field will correspond to the irradiated volume of the patient and will increase the safety and control of patient exposure to the target. The PC included in the MIC is designed on a “warm liquid” (or gas) and is a high-precision ionization chamber with coordinate sensitivity over the width of the irradiated target. The SC included in the MIC operates on gas and controls the direction of the incident beam to a given spot in the target. A version of the charge-sensitive preamplifier (QCD) and the SE system designed for experimental verification of the MIC prototype has been developed. The SCOO circuit working in conjunction with the MIC camera allows you to control the predetermined parameters of the irradiation of the patient’s target boundaries and turns off the accelerator if these parameters deviate from the initially specified ones.

This article discusses a methodology for assessing the effectiveness of a high-performance research platform. The assessment is carried out for the example of the "Informatika" Center for Collective Use (CCU) established at the Federal Research Center of the Institute of Management of the Russian Academy of Sciences, for solving new materials synthesis problems. The main objective of the "Informatika" Center for Collective Use is to conduct research using the software and hardware of the data center of the FRC IU RAS, including for the benefit of third-party organizations and research teams. The general characteristics of the "Informatika" Center for Collective Use are presented, including the main characteristics of its scientific equipment, work organization and capabilities. The hybrid high-performance computing cluster of the FRC CSC RAS (HHPCC) is part of the data center of the FRC IU RAS and also part of the “Informatika” Center for Collective Use. HHPCC provides computing resources in the form of cloud services as software (SaaS) and platform (PaaS) services. With the aid of special technologies, scientific services are delivered to researchers in the form of subject-oriented applications. Based on the analysis of the structure and operation principles of the Informatika Center, key performance indicators of the Center have been developed taking into account its specific tasks in order to characterize its various activity aspects (development, activities and performance). CCU efficiency evaluation implies calculation, on the basis of the developed indicators, of overall (generalized) indicators that characterize the CCU operation efficiency in various areas. An integral indicator is also calculated showing the overall CCU efficiency. To develop the overall performance indicators and the integral performance indicator, it is suggested to use the methods of weighted average and analysis of hierarchies. The procedure of determining partial performance indicators has been considered. Specific features of the choice of CCU performance indicators for solving new materials synthesis problems have been identified that characterize computing complex capabilities in the creation of a virtualization environment (peak performance of a computing system, real performance of a computing system on specialized tests, equipment loading with applied tasks and program code efficiency).