bluuebunny/crossref_metadata_2025 huggingface dataset:
The Extension of Field of Applications of Atomic-Force Microscope Hybrid Mode of Two-Probes Nano-Manipulator
Authors: Zhukov A. A.
Published: April 2024

The review of extension of fields of applications of hybrid mode of atomic-force microscope. This mode is the main for two-probes AFM-manipulator. Various methods of upgrades of the feed back system of the AFM whose essentially improve the signal-to-noise ratio in topography mapping are presented. Additionally, successful application of wide range of probes the flexible ones such as standard W probes and glass capillaries as well as rigid probes (sapphire probes with probe tips diameters of dozens of microns) are presented as well. We show the examples of wide application of such mode in measurements of conductivity and adhesion forces of the nanowhiskers on the Si substrate. Beside this, the application of hybrid mode in micro- and nanofluidics such as formation of drops of defined volumes, replacement of drops, their devision and merging are presented. The example of different techniques of manipulations are presented. The possibility of nanowhiskers replacement with liquid flow formed by AFM-probe, i.e. avoiding the direct tip-to-nanowhisker contact, are shown.
A Comprehensive Study of the Local Atomic Structure of Promising Ti-Containing Compounds
Authors: Averkiev I. K. , Bakieva O. R. , Kriventsov V. V.
Published: April 2024

A comprehensive study of the local atomic structure of titanium compounds obtained by mechanical activation (Ti–Al–C, Ti2AlC) and reference samples (Ti, TiH2) using EXAFS and EXELFS spectroscopy has been carried out. An analysis of the local atomic structure of titanium hydride shows that the presence of hydrogen expands the crystal lattice and leads to a change in the parameters of the local atomic structure. This change is observed both in the EXAFS and EXELFS spectra. It is shown that after mechanical activation, the coordination numbers decrease, which may indicate the formation of a multiphase system. Further annealing leads to the formation of the Ti2AlC compound, which is confirmed by the results of model calculations.
Structural Features and Phase Transitions in the Process of Dehydrogenation of Composite Based on Magnesium Hydride and Carbon Nanotubes
Authors: Kudiiarov V. N. , Elman R. R. , Kurdyumov N. E. , Pushilina N. S.
Published: April 2024

Composite based on magnesium hydride and carbon nanotubes, formed by mechanical synthesis in a high-energy ball mill, is a core–shell structure with magnesium hydride particles 4–8 μm in size, coated with nanosized particles of carbon and carbon nanotubes; in addition, the introduction of CNTs into the structure of magnesium hydride takes place. The introduction of carbon nanotubes into magnesium hydride creates trapping centers and channels for hydrogen diffusion, which leads to a decrease in the energy, required for hydrogen sorption and desorption by magnesium hydride by the spillover mechanism. In turn, the decrease in energy leads to a decrease in the temperature of the onset of hydrogen release from 200°C for pure magnesium hydride to 100°C for the composite and the appearance of a low-temperature maximum of hydrogen desorption intensity (180°C) for the composite. An in situ analysis of phase transitions during dehydrogenation showed that phase transitions in the composite are divided into three main stages. The first stage is characterized by defect annealing and structure relaxation without desorption of hydrogen; at the second stage, hydrogen is desorbed by the spillover mechanism without dissociation of hydrides; and at the third stage, hydrides are dissociated followed by desorption of the remaining hydrogen.
Synthesis and Investigations of Morphology and Structure of Fe2O3 Nanocoatings on Porous Al2O3, Obtained by Oxidation of Magnetron Deposited Fe Films
Authors: Valeev R. G. , Beltiukov A. N. , Chukavin A. I. , Eremina M. A. , Kriventsov V. V.
Published: April 2024

The results of studies of the morphology, crystal, local atomic and chemical structure of iron(III) oxide coatings on the surface of porous alumina with different morphology by scanning electron and atomic force microscopy, X-ray phase analysis, X-ray photoelectron spectroscopy, as well as fine structure spectroscopy of the near edge region are presented. X-ray absorption. Films of porous alumina were synthesized by the method of two-stage anodic oxidation of aluminum in aqueous 0.3 M solutions of sulfuric and oxalic acids. To change the pore diameter, some of the films were etched in a phosphoric acid solution. Samples of iron oxide nanocoatings were obtained by air oxidation of iron films deposited on porous alumina substrate matrices by magnetron sputtering at a temperature of 300°C for 3 hours. It is shown that oxidation leads to a twofold increase in the coating thickness of the control sample and is associated with an increase in the density of iron oxide compared to pure iron. With a change in the nanoporous structure on the surface of the substrates, the morphological features of the coatings change, which consists in the “overgrowth” of pores with iron oxide. That the control of the processes leading to such “overgrowth” will make it possible to carry out a directed change in the structure-sensitive properties of composite structures based on iron oxide.
Application of Some Techniques Using Synchrotron Radiation to the Study of a Promising Composite Thermoelectric Material SrTiO3–TiO2
Authors: Zavjalov A. P. , Lyubas G. A. , Sharafutdinov M. R. , Kriventsov V. V. , Kosyanov D. Yu.
Published: April 2024

The results of a study of biphase ceramics SrTiO3–TiO2, previously proposed as a promising n-type thermoelectric material, obtained using synchrotron radiation techniques at the shared research center “Siberian Synchrotron and Terahertz Radiation Center”, are presented. In particular, it has been demonstrated by in-situ heating X-ray diffraction that the reaction between the powder components SrCO3 (strontianite) and TiO2 (anatase) to obtain SrTiO3 (tausonite) is not the driving force in the preparation of ceramics by spark plasma sintering of the reaction mixture. For two spectral methods – X-ray luminescence and XANES spectroscopy, the spectrum of biphasic ceramics was compared with a model spectrum obtained from the spectra of single-phase ceramics as reference samples. The X-ray luminescence method revealed a shift to the high-energy region and a narrowing of the spectrum of biphase ceramics, which may indicate size quantization (the presence of a two-dimensional electron gas) in the system. Changes were found in the XANES spectrum of biphase ceramics in the region in which its shape can significantly depend on the symmetry of the nearest environment of Ti4+ atoms. However, it is difficult to interpret these data without numerical simulation.
Determining the Collimation Degree for a Coherent X-Ray Beam Using a Planar Multilens Interferometer
Authors: Zverev D. A. , Yunkin V. A. , Kuznetsov S. M. , Barannikov A. A. , Sorokovikov M. N. , Voevodina M. A. , Snigirev A. A.
Published: April 2024

A method is proposed for determining the degree of collimation of a coherent X-ray beam using a planar multilens interferometer. The method is based on analyzing Talbot images, which are periodic patterns of interference fringes formed by the interferometer at appropriate distances. The high sensitivity of the position and period of the interference fringes to the shape of the X-ray beam wave front makes it possible to determine the degree of its collimation, as well as to evaluate the coherent properties of the radiation. The effectiveness of the proposed approach has been experimentally demonstrated at the ID15B beamline of the ESRF synchrotron radiation source. A theoretical study has been carried out, and the corresponding results of computer simulation have been presented. The experimentally data obtained fully correspond to the theoretical estimates.
High-Energy Part of the Accelerator for the Compact Neutron Source DARIA: Drift Tube Linac
Authors: Kropachev G. N. , Kulevoy T. V. , Sitnikov A. L. , Vinogradov S. V. , Khabibullina E. R. , Skachkov V. S. , Sergeeva O. S
Published: April 2024

In the framework of the DARIA project (neutron source Dedicated to Applied Research and Industrial Applications) the 13 MeV, 162.5 MHz and 100 mA pulse proton linac is under development at the National Research Centre “Kurchatov Institute” – Kurchatov Complex for Theoretical and Experimental Physics. The linac includes RFQ (Radio Frequency Quadrupole) and DTL (Drift Tube Linac) sections. This article is devoted to the development of the DTL. The type of accelerating structure for creating high-frequency fields, which consists of a chain of multi-gap resonators, was determined. The optimal number of gaps in the resonators was selected. The choice of the main parameters and the analysis of various structures of the focusing periods were carried out. The results of the beam dynamics simulation in DTL are presented. The influence of Coulomb forces on particle dynamics in DTL was studied. The growth of the emittance in the DTL section was analyzed. The capabilities of the section for a wide range of input current and input beam emittance were considered.
Choice of the Target Material for a Compact Neutron Source at a Proton Energy of 20–100 MeV
Authors: Moroz А. R. , Kovalenko N. A.
Published: April 2024

Be, Nb, Ta and W are considered as candidate target materials for a compact neutron source. The thermal characteristics and the hydrogen diffusion coefficients are taken into account. Using the simulation of particle transport in the PHITS program, estimates are obtained for the neutron yield when the target is irradiated with protons of various energies. Different optimal materials correspond to different energy ranges. The best results at energies up to 20 MeV are shown by Be, 20–35 MeV by Nb, and above 35 MeV by Ta. The last two materials have an increased blistering resistance compared to beryllium, but lose in thermal conductivity. An increase in the energy of incident protons also leads to an increase in the number of neutrons generated per one source proton due to a reduced time of the Coulomb interaction between a particle and the target atom nucleus.
Resonant Neutron Reflectometry on a Compact Neutron Source
Authors: Nikova E. S. , Salamatov Yu. A. , Kravtsov E. A.
Published: April 2024

This paper presents an approach to solving the phase problem in neutron reflectometry (including polarized neutron reflectometry) based on the effect of resonant interaction of nuclei of gadolinium isotopes 155Gd and 157Gd with thermal neutrons. This effect is used to implement the reference layer method, which allows, based on the results of three experiments, to calculate the complex reflection coefficient of the sample under study. Knowledge of the complex reflection coefficient makes it possible to model-independent analysis of the interaction potential, both nuclear and magnetic. The main application of this approach is the study of the structure of layers and interfaces, as well as the determination of the magnetic state of multilayer metal nanoheterostructures. The theoretical basis of this method is given, which consists in deposition on the sample top of a gadolinium layer with known parameters, one of which can be varied in a controlled manner. The scheme of the experiment is described in detail using model numerical calculations. An experimental result is given for a simple single-layer niobium sample, for which the modulus and phase of the reflection coefficient were calculated. Promising directions for improving the method and possible directions for further work are proposed. The requests for the characteristics of a compact neutron source, necessary for the optimal implementation of the proposed method, are formulated.
Small-Angle Neutron Scattering Instrument for Compact Neutron Source DARIA
Authors: Pavlov K. A. , Kovalenko N. A. , Azarova L. A. , Kravtsov E. A. , Kulevoy T. V. , Grigoriev S. V.
Published: April 2024

Aspects of the experimental implementation of the small-angle neutron scattering (SANS) method on a compact neutron source are considered. A scientific justification of the demand for this type of instrument is formulated. A scheme for implementing the SANS method on a pulsed neutron source is proposed, which ensures high efficiency of using a neutron beam by limiting the operating wavelength range, and, as a result, maximizing the frequency and time-averaged power/intensity of the source. The physical parameters of the key elements of the facility, such as the cold neutron moderator, the beam chopper cascade, the collimation system, the sample unit and the wide-aperture position-sensitive detector, are described. It is shown that the small-angle scattering method can be implemented on a university-type pulsed neutron source.
Development of a One-Dimensional Counting Detector for Diffraction Experiments at a Synchrotron Radiation Beam
Authors: Aulchenko V. M. , Glushak A. A. , Zhulanov V. V. , Titov V. M. , Shekhtman L.I.
Published: April 2024

The article describes a one-coordinate detector for diffraction experiments on a synchrotron radiation beam. The detector is being developed at the Budker Institute of Nuclear Physics SB RAS. Until recently the Institute was developing gas one-coordinate detectors, in particular a one-coordinate detector with calculated channels OD-3M, based on the technology of multi-wire proportional cameras. To provide a spatial resolution of better than 100 microns at photon energy in a wide energy range (3–30 keV), it is necessary to use solid-state microstrip or matrix sensors in combination with specialized integrated registration circuits. The developed SOCOD detector, using a microstrip sensor based on gallium arsenide as a recording element, operates in the mode of direct counting of photons with an energy of more than 3–4 keV and a speed of up to 1 MHz/channel. The article gives a general description of the current version of the detector, the block diagram of the recording channel, the software that allows users to control the operation of the detector and display the results obtained, and the developed algorithm for leveling the trigger thresholds in the channels. The results of electronic tests, the work of the alignment algorithm and their discussion are presented.
Theoretical Study of Neutron Reflection from Thin Films and Layered Nanostructures Containing Highly Absorbing Gadolinium and Boron Isotopes
Authors: Salamatov Yu. A. , Kravtsov E. A.
Published: April 2024

The application of the method of phase-amplitude functions to the calculation of neutron propagation processes in layered media containing highly absorbing elements is described. This method allows us to simultaneously calculate the reflection, transmission and absorption coefficients of neutrons. It requires less computing resources than the other algorithms. A generalization of the method to matrix equations used in polarized neutron reflectometry is also presented. Examples of calculations of various characteristics of neutron propagation for layered resonator-type systems with a potential well are given.
Use of Special Devices for X-Ray Interferometric Investigation of Structural Imperfections in Single Crystals
Authors: Drmeyan H. R. , Vasilyan M. S.
Published: April 2024

A universal device for X-ray interferometric study of structural defects in single crystals has been designed, manufactured and tested. The device can serve both for scratching the surface of the interferometer crystal blocks and for bending it. A technology for generating dislocation in an interferometer block is also proposed. It has been experimentally proved that the moiré topographic patterns obtained using a double X-ray interferometer depend on the orientation of the reflection planes relative to the defect (dislocation). It is shown that multiple interferometers make it possible to simultaneously observe images of various structural imperfections. The results obtained make it possible to judge the spatial orientation of defects and the distribution of strain fields caused by these defects, i.e., strain fields can be visualized as X-ray moiré patterns. The results obtained in the work can form the basis for solving the inverse task, namely, the restoration of mechanical tension fields in the interferometer crystal blocks using the decoding of moiré patterns.
Сomposites with a Matrix Based on Niobium and Molybdenum Reinforced with Sapphire Fibers
Authors: Kiiko V. M. , Korzhov V. P. , Kurlov V. N.
Published: April 2024

Single-crystal sapphire fibers were obtained by the Stepanov method/EFG – Edge defined Film-fed Growth. The procedure for obtaining them is described. Mechanical testings of the fibers were carried out according to the presented scheme, and the dependences of the ultimate deformation and strength of the fibers on the length were determined. The dependences are power-law, and decrease with the length of the fibers. The strength of the obtained fibers corresponds to the world level and meets the conditions for their use as reinforcing for high-temperature composite materials. From workpieces containing layer-by-layer unidirectionally arranged sapphire fibers, niobium powder, metal foils of molybdenum and aluminum, layered-fibrous composites were obtained by solid-phase diffusion welding under load. Using scanning electron microscopy with X-ray analysis, the structure of the composites was studied, it was found that, in addition to the initial components, it includes intermetallic compounds of niobium, molybdenum and aluminum, as well as solid solutions of these metals formed in the technological process. As a result of mechanical testing of composite samples, deformation curves of load-deflection dependences were obtained, which, together with developed fracture surfaces, indicate the non-brittle nature of the fracture of composites containing brittle components. The dependences of the strength of composites on temperature in the range of 20–1400°C are obtained, which meet the requirements for high-temperature structural materials of this kind.
On the Radiation Stability of ZnO Powders Modified with Own Nanoparticles
Authors: Mikhailov M. M. , Yuryev S. A. , Lapin A. N. , Goronchko V. A.
Published: April 2024

Changes in the diffuse reflectance spectra (∆ρλ) and integral absorption coefficient (Δаs) in the range of 0.2–2.5 µm were studied after modification of zinc oxide powders with few µm particles (mZnO) via own nZnO nanoparticles of various concentrations in the range of 0.1–10.0 wt %. A decrease in the reflection coefficient (ρ) in the range of 0.4–1.0 µm and its increase in the range of 1.0–2.5 µm in the modified mZnO/nZnO powders was established. Electron irradiation (Е = 30 keV, F = 2 × 1016 cm–2) of mZnO, nZnO, and mZnO/nZnO powders with different concentrations of nanoparticles showed that the optimal concentration of nanoparticles is 5 wt %. The radiation stability of the modified powder at this concentration increased by a factor of 2.95, the radiation stability of a nanopowder is more than 2 times higher than that of a powder with particles a few microns in size. When irradiated with electrons all three types of powders form their own point defects, which absorb in the visible region, and free electrons, which absorb in the near-IR region.
Mechanism of Solid Solution Hardening: Quasilocalisation of Dislocation Kinks
Authors: Petukhov B. V.
Published: April 2024

The sensitivity of the mechanical properties of materials to violations of the translational invariance of the crystal lattice makes it possible to manipulate these properties in the desired direction by doping or creating solid solutions. The paper theoretically studies the mechanisms of such manipulation in relation to materials in which the mobility of dislocations is controlled mainly by the potential relief of the crystal lattice – the so-called Peierls relief. Due to the concentration of alloying atoms in dislocation nuclei, which play the role of traps for these atoms, the dynamic properties of dislocations change, which also leads to modification of the macroscopic mechanical properties of the material. The theory of the effect of doping on the kink mechanism of overcoming the Peierls barriers is constructed taking into account the disordered content of solution atoms in dislocation nuclei. Correspondingly, the direct description of the kinetics of elementary processes characteristic of kinks has been replaced by a statistical description. The multidirectional effect of fluctuations in the solutes distribution, which increase the rate of formation of pairs of kinks, but inhibit the propagation of kinks along dislocation lines, is considered. Inhibition of kinks can lead to an anomalous nature of their mobility, so-called quasilocalisation. The conditions for the predominance of the accelerating or inhibiting factor corresponding in macroscopic terms to the hardening or softening of the material are found.
Properties of Deformable Medium Element as a Factor of Superplasticity of Metallic Materials
Authors: Solov’eva Yu. V. , Lipatnikova Ya. D. , Vovnova I. G. , Starenchenko V. A.
Published: April 2024

Theoretical study of the phenomenon of superplasticity of metallic materials has been carried out. Numerical calculations were performed on the basis of a two-level finite element model of an elastoplastic medium. The plastic properties of the deformable medium element determining the deformation by uniaxial tension in superplasticity mode were found. It was shown that depending on the shape of the stress-strain curve (σ–ε) of the medium element, the various types of plastic flow localizations were observed at the macroscale level. The nonmonotonic dependence σ–ε of the deformable medium element having single maximum was determined as the condition for the appearance of a stable fracture neck. In the case when the dependence σ–ε characterized by the strengthening of the elementary volumes with two maxima, a propagating (running) neck was observed, then a second (counter) neck appeared, while further tension led to the appearance of the third stable neck in which fracture occurred. In the case of more complex oscillating shape of σ–ε curve the multiple running necks were observed. The movement of the multiple necks propagating along the sample leads, ultimately, to a uniform picture of the deformation and made it possible to achieve the strain values observed in superplasticity mode.
The Method for Determining the Exact Single Crystal Orientation with Simultaneous X-Ray Energy Correction Using the Spectrum of Diffraction Losses
Authors: Klimova N. B. , Snigirev A. A.
Published: April 2024

The intensity loss of transmitted beam due to parasitic diffraction (glitches) is an inherent property of single-crystal X-ray optics. This effect can lead to a weakening of the radiation, up to its complete disappearance. Therefore, understanding the effect of diffraction loss is essential for any experiments that use single-crystal optics. We present theory of glitch formation and demonstrate its application to experimental data to determine the orientation and cell parameters of optical elements made of the single-crystal diamond. A systematic error was found in determining the absolute energy of X-ray, which occurs due to the wrong monochromator tuning (an error in determining the absolute 2θ angle). The described error very often occurs during the experiment as a result of the fact that determining the absolute 2θ angle of the monochromator crystal is a technically difficult task. Simultaneous determination of the orientation and lattice parameters of the studied sample, together with the compensation of the systematic error in the monochromator tuning, made it possible to significantly improve the accuracy of processing the obtained data.
Effect of Annealing Conditions on the Formation of a Nanocrystalline Phase in TiOx Films
Authors: Nezhdanov A. V. , Zhukov A. O. , Shestakov D. V. , Vinogradova L. M. , Skrylev A. A. , Ershov A. V. , Pavlov D. A. , Andrianov A. I. , Markelov A. S. , De Filpo G. , Baratta M. , Mashin A. I.
Published: April 2024

Annealing of amorphous TiOx films obtained by electron-beam evaporation under atmospheric conditions at temperatures from 300 to 400°C is found to lead to the formation of an anatase crystalline phase. According to Raman spectroscopy data, the increase in the fraction of the the crystalline phase stops at an annealing temperature above 350°C. According to the results of X-ray phase analysis, the average crystallite diameter is about 23 nm. Electron microscopy studies have shown that, upon annealing, the near-surface layer (15 nm thick) crystallizes in the films, and TiO2 nanocrystals with sizes from 4 to 10 nm are formed in the bulk. As the depth increases, the number of nanocrystals decreases.
Investigation of Morphology and Electrical Properties of Structures Based on the Heterojunction Monocrystalline Si/Microcrystalline ZnO
Authors: Semenov A. R. , Litvinov V. G. , Kholomina T. A. , Ermachikhin A. V. , Rybin N. B.
Published: April 2024

The results of an experimental study of the surface morphology of zinc oxide films and the electrical properties of structures based on the monocrystalline Si/microcrystalline ZnO heterojunction are presented. The structure of zinc oxide films grown in an atmosphere of argon and oxygen is analyzed, and the size distribution of nanoscale fibers grown on its surface is obtained. The capacitance-voltage characteristics of the In/ZnO/n-Si/Al and Au/ ZnO/n-Si/Al heterostructures have been simulated. Based on the calculations and comparison of experimental and model dependences, the concentration of free charge carriers in the sample and the position of the Fermi level were determined, the presence of a fixed charge in the structure was revealed, the density of surface states was found based on the ratio of the voltage applied to the structure and the surface potential at the interface of the materials of the layers of structures. The value of the built-in surface charge is calculated. The interrelation of the upper contact material with the volt-farad and volt-ampere characteristics of the structure is investigated. The resistance of the formed zinc oxide films is calculated. The prevailing charge transfer mechanisms are discussed. The influence of technological modes of obtaining zinc oxide films obtained by spray pyrolysis on the structure of the surface, the effective capacity of the structure, the density of electronic states, the processes of charge carrier transfer in samples under the action of an electric field is analyzed.
Features of Formation of Surface Layers of Titanium Alloy VT6 under Conditions of N+ Ions Implantation
Authors: Vorobyov V. L. , Bykov P. V. , Gilmutdinov F. Z. , Ulyanov A. L. , Bayankin V. Ya.
Published: April 2024

The effect of implantation of N+ ions on the chemical composition and atomic structure of the surface layers of titanium alloy VT6 is investigated. The accumulation of nitrogen in the surface layers up to concentrations of 30 at % and more and the formation of chemical compounds of titanium nitride TiN in the form of phase inclusions is shown. Presumably, this is due to processes of chemical nature, in particular, the chemical activity of titanium atoms, their tendency to interact with nitrogen atoms. In addition, despite the fact that in the conditions of ion bombardment, the integral oxygen concentration in the surface layers decreases due to sputtering, nevertheless, oxidation of the components of the titanium alloy VT6 is observed in deeper layers. Presumably, both oxygen from the natural oxide layer and from the residual atmosphere of the vacuum chamber, penetrating into deeper surface layers during irradiation, participate in the oxidation of titanium alloy components. The accumulation of nitrogen, the formation of titanium nitrides and the oxidation of the components of the titanium alloy VT6 indicate a significant role of chemical processes in the formation of the structural-phase state of the surface layers of titanium alloy VT6 under the conditions of implantation of N+ ions.
Application of Synchrotron Radiation Diffraction Techniques for Optimizing the Sintering Trajectory of Al2O3–Ce:(Y,Gd)AG Composite Ceramics
Authors: Zavjalov A. P. , Kosyanov D. Yu.
Published: April 2024

The development of most branches of lighting technology poses the challenge of developing advanced high-power white light-emitting diodes. Their design involves the combination of two basic elements – a high-power blue light-emitting diode or a laser diode with a yellow phosphor converter that can withstand high thermal loads. Recently, the development of solid-state (primarily ceramics) phosphors based on Ce:YAG, co-doped with the so-called “red” ions with high thermal conductivity and thermal stability, has been actively pursued. Additionally, the possibility of creating on their basis composite structures with a secondary thermostable phase of corundum α-Al2O3, which has many times higher thermal conductivity at a close coefficient of thermal expansion, is being considered. The development of a sintering map for complex systems based on solid ceramics solutions requires mandatory control of their structural-phase state by X-ray diffraction. However, laboratory equipment is not always sufficient to understand the processes occurring during sintering. Therefore, in this work, on the example of Al2O3–Ce:(Y,Gd)AG biphase ceramics, we optimized the trajectory of their sintering using diffraction of synchrotron radiation. The composites were synthesized by the method of reactive spark plasma sintering of powders of the initial oxides. It is shown that at the fixed applied pressure of 30 MPa and an isothermal holding for 15 min, a single phase of the Ce:(Y,Gd)AG solid solution is formed only at temperatures of at least 1450°C. At such high sintering temperatures, signs of recrystallization are observed due to the proximity of eutectic melting. Increasing the exposure time to 30 min makes it possible to lower the temperature of formation of the biphasic structure to 1425°C and prevent undesirable recrystallization. However, the subsequent increase in pressure to 90 MPa leads to the coexistence of several variations of the YAG-type phase in the system.
Nuclear Stopping for DFT Potentials with Attraction Well
Authors: Babenko P. Yu. , Zinoviev A. N.
Published: April 2024

Using the interaction potentials obtained in the framework of the density functional theory, the nuclear stopping powers are calculated for the H, D, T–Be, C, W, systems necessary for calculating the plasma–wall interaction in thermonuclear research, as well as for the Kr–Si, Kr–Ge, O–Si systems, used in ion implantation into semiconductors. In the collision energy range 10–1000 eV, the obtained data differ from the SRIM data by 15–70%. The presence of a potential well leads to the appearance of an additional peak in the nuclear stopping power at low energies. A comparison of the classical calculations of the transport cross section with the semiclassical ones showed their identity at energies up to 0.3 eV.
The Size Dependence of the Adsorption Properties of Nickel Clusters on the Surface of Aluminum Oxide
Authors: Magkoev Т. Т. , Nadimi E. , Tvauri I. V. , Zaalishvili V. B. , Ashkhotov O. G. , Ashkhotova I. B.
Published: April 2024

Despite the recent activity in the field of research on the properties of systems formed by the adsorption of metal atoms on the surface of oxides, many fundamental issues remain open. Finding out the fundamental features of the behavior of systems of the type under consideration will improve the technological basis for the practical development and application of existing materials. In this regard, in this work, studies of the Ni/Al2O3/Mo(110) system were carried out in ultrahigh vacuum using surface diagnostics methods. Using X‑ray photoelectron and electron Auger spectroscopy, low-energy ion backscattering spectroscopy, and infrared Fourier spectroscopy, it is shown that electronic and adsorption properties of nanoscale nickel clusters on the surface of aluminum oxide significantly depend on the size of the cluster. The properties of clusters no larger than 2 nm are determined by the formation of a bond polarized towards the oxide substrate at the Ni/Al2O3 interface. With the growth of the cluster, depolarization of this connection occurs with the redistribution of electron density to lateral bonds between Ni atoms. Such a dimensional dependence makes it possible to program the properties of metal clusters and the metal oxide system as a whole, in particular, to achieve the required electronic and adsorption-reaction parameters.
X-Ray Transfocators a Tunable X-Ray Focusing Apparatus Based on Compound Refractive Lenses
Authors: Narikovich A. S. , Lyatun I. I. , Zverev D. A. , Panormov I. B. , Lushnikov A. A. , Sinitsyn А. V. , Barannikov A. A. , Medvedskaya P. N. , Korotkov A. S. , Snigirev A. A.
Published: April 2024

This paper presents a new generation of ultra-compact and high-vacuum cooled X-ray refractive lens-based transfocators for collimation, transport, and focusing of hard X-rays. The transfocator is an optical device capable of changing the position of focus depending on the number of X-ray refractive lenses, which are exposed along the optical path of X-ray radiation. The design features of the device allow the individual optical elements to be controlled independently of each other, providing a more flexible adjustment of the focal distance for a wide range of applications. The small overall dimensions and light weight of the devices allow them to be integrated into any synchrotron radiation station.
Modeling of Multilayer Structures with Tunable Optical Characteristics
Authors: Tolkach N. M. , Vishnyakov N. V. , Litvinov V. G. , Sherchenkov A. A. , Trusov E. P. , Glukhenkaya V. B. , Pepelyaev D. V.
Published: April 2024

Phase transition materials, in particular chalcogenide glassy semiconductors and Ge–Sb–Te system materials are of interest for application in optical information processing technologies. The uniqueness of these materials lies in the fact that they have a low-energy, fast and reversible phase transition, leading to a significant change in the refractive index in the infrared region of the optical spectrum. The model calculations carried out in the work made it possible to investigate the transformation of optical properties in multilayer structures consisting of SiO2, Si, Si3N4 layers and an active layer of a phase transition material when its phase state changes. The aim of these studies was to fulfill the condition of the lowest optical losses during transmission and reflection of radiation of 1550 nm in such structures in the case of amorphous and crystalline states of the active layer, respectively. As a result, the nine-layer “SiO2//111 nm Si/277 nm SiO2/111 nm Si/251 nm SiO2/10 nm Ge2Sb2Se4Te/241 nm SiO2/110 nm Si/276 nm SiO2/112 nm Si//SiO2” structure that most satisfies the specified conditions was designed.
Specific Aspects of Design and Use of Instruments for Space EUV Experiments
Authors: Kuzin S. V. , Bogachev S. A. , Kirichenko A. S. , Pertsov A. A.
Published: April 2024

The specific aspects of design and operation of space instruments for recording radiation and images in the extreme ultraviolet (EUV) range of the spectrum are considered. The main factors affecting the reliability of EUV instruments are contamination temperature regime pressure drop acoustic pressure shocks vibration overloads at the launch stage weightlessness and radiation damage. These factors are often interconnected and operate in a complex manner. The analysis of the influence of these factors on the main characteristics of the instruments and the possibilities of its reduction is carried out.
Surface Modification of Melamine-Formaldehyde Particles in Ne and Kr Plasma
Authors: Polischuk V. A. , Balabas M. V. , Dzlieva E. S. , Gorbenko A. P. , Ermolenko M. A. , Karasev V. Yu.
Published: April 2024

Changes in the surface of micron-sized melamine-formaldehyde microparticles in dusty structures in a glow-discharge plasma in Ne and Kr were experimentally studied. Microparticles were placed in plasma-dust structures with subsequent extraction. Two effects depending on the exposure time in plasma were established in the experiment: a comprehensive decrease in the particle size and a change in the morphology of their surface. A model was considered, which makes it possible to estimate the contribution of various mechanisms of the interaction of charged plasma particles with the surface of melamine-formaldehyde. The estimates obtained are in good agreement with the experimental data.
Study of the X-Ray Optical and Mechanical Characteristics of C/Si and B4C/Si Multilayer Mirrors
Authors: Smertin R. M. , Barysheva M. M. , Garakhin S. A. , Zorina M. V. , Zuev S. Yu. , Polkovnikov V. N. , Chkhalo N. I. , Radishchev D. B.
Published: April 2024

The X-ray optical and mechanical properties of dielectric multilayer mirrors based on pairs of C/Si and B4C/Si materials are synthesized and studied. The mirrors are optimized for a wavelength of 13.5 nm. The parameters of the deposition process are found that simultaneously ensure the fulfillment of three conditions: relatively high reflection coefficients at the operating wavelength, near-zero mechanical stresses in the film, and the absence of electrical conductivity. At zero internal stresses, the reflection coefficient of C/Si multilayer mirrors deposited on superpolished silicon substrates at an operating wavelength of 13.5 nm is R = 11%, the spectral bandwidth is Δλ = 0.33 nm. The B4C/Si mirror provides the following characteristics: R = 8.2%, spectral bandwidth Δλ = 0.3 nm. However, blistering has been found in B4C/Si multilayer mirrors, i.e., the appearance of bubbles on the film due to the accumulation of hydrogen inside, which excludes their use for deposition on commercially available microelectromechanical system micromirrors. The deposition of a C/Si coating made it possible for the first time to obtain a workable system that reflects X-rays at an operating wavelength of 13.5 nm. The reflection coefficient is about R ~ 3%. The low value of the reflection coefficient is due to the high, about 1.5 nm, microroughness of the surface of the microelectromechanical system micromirrors. The study performed indicates the fundamental possibility of creating a matrix X-ray optical element for modulating the spatiotemporal characteristics of X-ray beams.
Unipolar and Subcycle Extremely Short Pulses: Recent Results and Prospects (Brief Review)
Authors: Arkhipov R. M , Arkhipov M. V , Pakhomov A. V , Obraztsov P. A , Rozanov N. N
Published: April 2024

In recent years, progress has been made in obtaining extremely short electromagnetic pulses up to single-cycle and unipolar half-cycle pulses. For pulses with such a dependence of the electric field strength on time, the behavior and properties of such radiation and its interaction with matter acquires a number of new features. For extremely short unipolar pulses an important role in the interaction with matter is played by the electric pulse area (the integral of the electric field strength over time at a given point in space). The review presents the latest theoretical and experimental results in the field of obtaining and interaction of extremely short pulses with extended resonant media and individual microobjects (atoms, molecules, nanostructures). The results of new publications are discussed, in which phenomena are predicted that arise during the coherent propagation of extremely short pulses in resonant media—self-compression and self-stopping of a pulse in a homogeneous medium. Particular attention is paid to the effect of ultrashort pulses on microobjects from the point of view of the recently introduced concept of “interference” of pulse areas (electrical area and envelope area). The research results presented in the review relate to a new direction in modern optics that has emerged recently—“Optics of unipolar and subcycle light,” which is becoming an actively developing area of modern physics.
Two-Photon Laser Lithography of Functional Microstructures of Integrated Photonics: Waveguides, Microcavities, and Prism Input/Output Adapters of Optical Radiation
Authors: Maydykovskiy A. I , Apostolov D. A , Mamonov E. A , Kopylov D. A , Dagesyan S. A , Murzina T. V
Published: April 2024

The development and optimization of methods for creating functional elements of micron and sub-micron sizes for photonic integrated circuits is one of the main tasks of nanophotonics. Two-photon laser lithography is actively developing now to form three-dimensional structures with subwave resolution. Results of this development are reported and it is shown that the use of optimized lithography schemes, the spatial filtering of laser beam used, and the introduction of laser dyes into polymer lead to the formation of optically homogeneous high-quality bulk microstructures with characteristic features down to 300 nm with necessary functional properties. The capabilities of optimized two-photon laser lithography are demonstrated by examples of ring microcavities and optical waveguides with prism input/output adapters located above a substrate. Optical losses upon the coupling of 405-nm radiation into a waveguide using a printed prism adapter was no more than 1.25 dB.
Magnetic State of Layered Cobalt Chalcogenides Co7Se8 and Co7Te8
Authors: Piskunov Yu. V , Ogloblichev V. V , Sadykov A. F , Akramov D. F , Smol'nikov A. G , Gerashchenko A. P , Selezneva N. V , Baranov N. V
Published: April 2024

The structural and magnetic properties of the Co7Te8 layered compound have been studied for the first time using X-ray diffraction, measurements of the magnetic susceptibility, and nuclear magnetic resonance spectroscopy on 59Co nuclei. The nuclear magnetic resonance study of Co7Se8 selenide with the same structural type (NiAs) as Co7Te8 has also been performed for the first time. In contrast to Co7Se8, the ordering of vacancies and Co atoms in cation layers is absent in the Co7Te8 compound, and its crystal structure is more planar and is characterized by a significantly smaller ratio c0/a0 compared to Co7Se8 (a0 and c0 are the basic lattice parameters of NiAs). The components of the magnetic shift and electric field gradient tensors at the location of Co nuclei have been determined. A significant local charge and spin inhomogeneity of the co-mpounds has been revealed. The hyperfine coupling constant in Co ions has been estimated from the te-mperature dependences of the shift and susceptibility in Co7Te8. An anisotropic increase in the interatomic distances does not increase the localization ofelectrons and does not lead to the appearance of magnetic moments on Co atoms in Co7Te8. This compound remains a Pauli paramagnet down to the lowest tempe-ratures.
Systematic Effects in the Measurement of the Lifetime of the Neutron in Magnetic Traps of Ultracold Neutrons
Authors: Ezhov V. F , Ryabov V. L
Published: April 2024

Possible systematic effects in experimental measurements of the lifetime of the neutron using magneto-gravitational traps to store ultracold neutrons have been discussed. Methods for the online detection of possible losses, including depolarization losses and a small heating of neutrons stored in a trap, have been proposed.
Long-range Multiparticle Interactions Induced by Neutrino Exchange in Neutron Star Matter
Authors: Krivoruchenko M. I
Published: April 2024

Forces with a large radius of interaction can have a significant impact on the equation of state of matter. Low-mass neutrinos generate a long-range potential due to the exchange of neutrino pairs. We discuss a possible relationship between the neutrino masses, which determine the interaction radius of the neutrino-pair exchange potential, and the equation of state of neutron matter. Contrary to previous statements, the thermodynamic potential, when decomposed into the number of neutrino interactions, vanishes in any decomposition order, except for the interaction of two neutrons. In the one-loop approximation, long-range multiparticle neutrino interactions are stable in the infrared region for all neutrino masses and do not affect the equation of state of neutron matter or the stability of neutron stars.
Magnetic Field Effect on the Formation of Ultracold Plasma
Authors: Bronin S. Ya , Vikhrov E. V , Zelener B. B , Zelener B. V
Published: April 2024

The molecular dynamics method is used to simulate the formation of ultracold plasma under continuous ionizing irradiation in a quadrupole magnetic field with the gradient of the magnetic field along the axis of symmetry equal to 0, 30, 150, and 500 G/cm. An increase in the magnetic field promotes an increase in the plasma density owing to the trapping of some part of fast electrons by the quadrupole magnetic field.
Electronic Spectrum Features under the Transition from Axion Insulator Phase to Quantum Anomalous Hall Effect Phase in an Intrinsic Antiferromagnetic Topological Insulator Thin Film
Authors: Men'shov V. N , Chulkov E. V
Published: April 2024

In this paper, we investigate the electron topological states in a thin film of intrinsic antiferromagnetic topological insulator, focusing on their relationship with the magnetic texture. We consider a model for the film with an even number of septuple-layer blocks, which is subject to transition from the phase of an axion insulator to the phase of quantized Hall conductivity under an external magnetic field. In the continuum approach, we model an effective two-dimensional Hamiltonian of the thin film of a topological insulator with non-collinear magnetization, on the basis of which we obtain the energy spectrum and the Berry curvature. The analysis of topological indices makes it possible to construct a topological phase diagram depending on the parameters of the system and the degree of non-collinearity. For topologically different regions of the diagram, we describe the edge electronic states on the side face of the film. In addition, we investigate the spectrum of one-dimensional states on the domain wall separating domains with the opposite canting angle. We also discuss the results obtained and the experimental situation in thin films of the MnBi2Te4 compound.
Logarithmic Relaxation of the Nonequilibrium State of the Charge Density Wave in TbTe3 and HoTe3 Compounds
Authors: Frolov A. V , Orlov A. P , Voropaev D. M , Khadzh-azzem A. , Sinchenko A. A , Monso P.
Published: April 2024

The measurements of electronic transport including the dynamic properties of the charge density wave (CDW) in the quasi-two-dimensional compound HoTe3 have been performed. The effects of the slow relaxation of the nonequilibrium state of the CDW during isothermal exposure in the zero current mode, previously observed in TbTe3, have been discovered and studied. A significant increase in the exposure time made it possible to clearly demonstrate that the relaxation is logarithmic. Relaxation features were studied in different temperature and time ranges. The data obtained indicate the glassy behavior of the CDW pinning centers in rare-earth tritellurides.
Vanadium-Containing Planar Heterostructures Based on Topological Insulators
Authors: Petrov E. K. , Silkin I. V. , Kuznetsov V. M. , Men'shchikova T. V. , Chulkov E. V
Published: April 2024

Vanadium-containing heterostructures consisting of an ultrathin magnetic film on the surface of a nonmagnetic topological insulator have been studied theoretically. A method has been demonstrated to control the Dirac point shift in the k space, which is a length measure of an exotic flat band appearing upon the formation of domain walls on the surface of antiferromagnetic topological insulator. The Dirac point shift is inversely proportional to the group velocity of electrons at the Dirac point and is proportional to the degree of localization of the topological state in the magnetic film. The shift is controlled by selecting a substrate with a certain work function. Particular systems have been proposed for the experimental study of flat band features in antiferromagnetic topological insulators.