Том 13, № 2 (2019)

Conventional Mo/Si mirrors and mirrors with B₄C and Be barrier layers, designed for reflection at wavelengths around 13.5 nm, are fabricated using magnetron sputtering and studied. Their reflectance is measured at different grazing angles and at different wavelengths. Four-component multilayer mirrors of the Mo/Be/Si/B₄C type are shown to surpass, in terms of the reflection coefficient, their Mo/Si and Mo/Si/B₄C counterparts by 2 and 1%, respectively, at wavelengths of incident radiation of 12.4, 12.7, 13.0, and 13.5 nm.

Mo/Y multilayer mirrors designed to operate in the range of 9–11 nm are considered. The dependence of the internal stress of such mirrors on the molybdenum fraction is studied for the first time. It is shown that structures with zero stress are characterized by a reflection coefficient of about 6%. The experimentally obtained maximum reflection coefficient (30%) corresponds to a stress of –160 MPa. The influence of a buffer layer of boron carbide on the internal stress and reflectance factor of the Mo/Y mirrors is investigated. A Cr/Y structure is proposed for compensation of elastic deformations of the substrate in manufacturing highly reflective Mo/Y multilayer mirrors.

The RADEX pulsed neutron source based on a linear proton accelerator at the Institute for Nuclear Research, the Russian Academy of Sciences, has one vertical channel with a 4-m path length and three horizontal channels with path lengths of approximately 10, 20, 30, and 50 m. The source is characterized by an unconventional configuration: the target and the water moderator are located perpendicularly to the proton beam; as a result, the neutron spectrum is enriched with epithermal and cascade neutrons. Using the source, investigations in the fields of nuclear physics, condensed-matter physics and nanostructures can be performed. The results obtained using various path lengths of horizontal channels of the RADEX neutron source are presented. Test measurements are conducted and direct beam spectra for the horizontal neutron channels and neutron diffraction patterns of test samples are obtained. The resolution for different path lengths of the neutron source is determined. The possibility of performing phase analysis is demonstrated.

The peculiarities of the surface topography that arise as a result of the sputtering of Si single-crystal substrates of different orientations with sputtered thin films under irradiation with Ar⁺ and He⁺ ion beams with energies in a broad energy range are considered. It is shown that the modified-layer thickness depends significantly on the irradiation dose. The best surface homogeneity of a Si single crystal with different orientations can be reached under simultaneous irradiation with Ar⁺ and He⁺ ions in a ratio that is close to 1 : 1.

The mechanisms of microinhomogeneity formation in epitaxial films with negative (\(\varepsilon < 0\)) and positive (\(\varepsilon > 0\)) values for the mismatch of the film and substrate lattice periods are considered. It is shown that at annealing temperatures up to 1100°C the lattice parameter barely changes and there are regions enriched with cation and anion vacancies at the boundary of inclusions. It is established that the share of the volume occupied by microinhomogeneities is determined by the parameter of nonstoichiometry \(\gamma ,\) which can be distributed unevenly. It is shown that the formation of defects in the oxidation process is more active than in the case of reduction. The possibility of the existence of a concentration gradient of Fe⁴⁺ ions in the film thickness is established. The efficiency of the violation of coherence of matching the imperfect region with the matrix and stress relief by the diffusion of vacancies to the interface is proved.

The structure and composition of iron ore (hematite) powders before and after treatment with weak pulsed magnetic fields are studied with scanning electron microscopy, scanning probe microscopy, X‑ray microanalysis, and Mössbauer spectroscopy. Hematite samples, which are structure-forming elements during the preparation of hexagonal barium and strontium ferrites after their grinding in an attritor, are objects of the research.

A comparative analysis of the structural evolution of MGA-95 and ESPA1 polymer composite porous films is performed by plotting the radial distribution functions of atoms using empirical X-ray scattering intensity curves and the thermophysical parameters of melting are calculated using data from differential scanning calorimetry (DSC). In the case of the water-saturated MGA-95 sample, the atomic density in the first coordination sphere of the cellulose acetate macromolecule is shown to decrease due to the breaking of intramolecular hydrogen bonds. The atomic density of coordination spheres with radii corresponding to the lattice parameters decreased suggesting spatial disorder of the macromolecules. The DSC data for the MGA-95 film (the enthalpies of melting of the dry and water saturated samples are ΔH = 8.57 and 6.55 J/g, respectively) suggests that sorption of water molecules leads to a decrease in the degree of crystallinity due to a change in the crystalline fractions in the polycrystals. In the case of the ESPA1 composite film, a decrease in the radius and an increase in the atomic density of the first coordination sphere are indicative of the orientational disorder of amorphous phase molecules upon the sorption of water. The appearance of additional coordination spheres with R₂ = 3.88 and R₃ = 5.26 Å in the swollen ESPA1 sample suggests the quantitative redistribution of crystal phases in the substrate material. A detailed analysis of endothermic peaks on the DSC curve shows that the ratio of low- and high-temperature phases varies from 64% : 36% in the dry sample up to 51% : 49% in the water saturated sample at almost identical enthalpies of melting of ΔH = 12.18 and 11.66 J/g, respectively.

Works on the creation of composite materials with a biologically active coating are carried out. The bioactive coating is formed from an aqueous suspension of hydroxyapatite. Various means of application are proposed: vacuum impregnation, its combination with centrifugation and ultrasonic treatment. Their comparative evaluation is carried out. The effect of various factors (matrix material, coating process, heat treatment) on the features of surface-layer formation and its strength characteristics is studied.

The possibility of studying the erosive wear of protective coatings of full-scale aircraft by means of a mobile heterogeneous jet flow of limited area is considered and substantiated as an alternative to traditional research methods based on the use of scale models of samples, wind tunnels, and water-hammer test benches. Experimental data on the destruction of coatings as a function of the time of exposure to a jet flow of limited area are given, which show a linear dependence of the area of the destroyed coating on time. A mathematical model is proposed for calculating coating-material wear. The components of a feasible experimental device operating on these principles are described.

The emission of X-ray quanta, neutrons, and charged particles from deuterated structures under X-ray irradiation is studied. Targets (deuterated chemical-vapor-deposited (CVD)-diamond, palladium, zirconium, and titanium) are irradiated with the use of an X-ray tube equipped with a polycapillary lens with an energy of up to 30 keV and an X-ray tube equipped with a collimator with an energy of up to 25 keV. Different types of detectors, such as a multichannel neutron detector based on He-3 counters, a CR-39 plastic track detector, and silicon surface barrier detectors, are used. The emission of neutrons with an energy of above 10 MeV and alpha particles with an energy range of 7–15 MeV is revealed. This result indicates the possibility of stimulating multiparticle fusion reactions between deuterium nuclei in solid deuterated structures. The analysis of X-ray fluorescence spectra demonstrate the existence of “additional” peaks, which cannot be identified by any characteristic X-ray fluorescence line. Their appearance cannot be associated with any known element or diffraction process. The nature of the origination of the “additional” peaks requires special study.

Using a previously developed procedure for predicting the parameters of betavoltaic cells, we carry out calculations for cells based on a radioactive film enriched with ⁶³Ni up to 50% and real silicon structures, namely, a Ni/n–Si Schottky barrier and a p⁺–n diode. The procedure includes Monte Carlo calculation of the depth-dependent rate of the generation of β radiation by excess carriers and an experimental determination by SEM of the probability of their collection for specific structures. The need for such calculations is associated with the development of new possibilities of nickel enrichment with a radioactive isotope. We obtain achievable values of the short-circuit current, open-circuit voltage, filling factor, and cell power, which allows not only prediction of the parameters of such cells but also optimization of their structure. It is most expedient to use optimized p–n junctions in such cells.

The possibility of analytically calculating ion energy losses in the velocity interval of 1–10 au, where energy losses reach their maximum value, is considered. In this interval, the charge-exchange processes (electron capture and loss by an ion) lead to the fact that the average effective charge differs from the nuclear charge. The use of expressions for the average charge of ions passing through a carbon target in the Bethe—Bloch formula makes it possible to determine the ion velocities at which the energy losses reach their maximum and also the maximum ion energy losses. The performed calculations of the energy losses of ions with nuclear charges of Z = 4–10 agree quantitatively with the semiempirical (SRIM) and theoretical (PASS) results.

The structure and properties of the near surface layer of diamond after high-fluence irradiation at elevated temperatures with 30-keV Ar⁺, Ne⁺, N⁺, \({\text{N}}_{{\text{2}}}^{ + }\) and C⁺ ions are studied. Dynamic annealing at temperatures above 500°С results in recrystallization of the diamond phase only in the case of irradiation with carbon ions, and irradiation with impurity ions causes graphitization of the ion-modified layer of diamond. According to Raman spectroscopy and reflection high-energy electron diffraction data, a nanographite structure is formed in the modified layer when irradiated with noble-gas ions. When irradiated with carbon ions, diamond grows and recrystallizes with a thin (~1 nm) graphite-like layer on the surface. In the case of nitrogen ions, a graphite layer is observed up to 720°С. Graphite-like layers on the surface of diamond are thermostable and, according to X-ray photoelectron spectroscopy, are layers of sp² carbon. The Raman spectroscopy of visible light shows the different optical transparency of ion-induced structures on the surface of diamond, which correlates with the resistivities. The diamond structure disordered during ion irradiation at room temperature and the nanographite structure are more transparent than the graphite structure.

Carbon films 50–180 nm thick on nickel substrates are fabricated by the ion sputtering of graphite and the deposition of heavy hydrocarbons from the gas phase with simultaneous electron irradiation. Irradiation results in the formation of bonds in carbon films due to the sp and sp³ hybridization of orbitals (sp and sp³ bonds), mainly, sp³ bonds. A fraction of these bonds does not change with growth in the electron energy; it increases three-fold with a reduction in the temperature and an increase in the electron current density. Electron irradiation enhances the film microhardness which exceeds 12 GPa. The films, prepared by heavy hydrocarbon deposition, contain CH_n bonds and a small fraction of sp³ bonds. The maximum value of the microhardness of the hydrocarbon films is no more than 4.5 GPa. The analysis of the proposed model of the kinetics of forming different allotropic phases in a carbon film to be deposited shows that a temperature reduction changes the specific volume of an atom in the lattice, while under conditions of simultaneous electron irradiation, it appreciably increases the content of the phase with sp³ bonds. The effect of spⁱ-bond breakage during electron-beam-assisted deposition weakly depends on the electron energy. The weak excitations of electrons of carbon atoms can also result in the formation of sp³ bonds and increases their concentration with growth in the electron current density.

A procedure for simulating the scattering of atomic particles at amorphous and crystalline targets is described in the binary collision approximation. The influence of thermal vibrations, choice of the potential, and the inclusion of inelastic energy losses are analyzed using the simulation of hydrogen-atom scattering at a tungsten surface as an example. The coefficients of reflection from crystalline, polycrystalline, and amorphous surfaces are compared.

A custom-built gas cluster ion source with an energy up to 20 keV is constructed. Ar, CO₂, N₂, and O₂ are used as the working gases. The clusters are formed by metal conical nozzles with critical diameters of 65−135 um and a cone angle of 14°. To facilitate evacuation of the chambers we use the pulse mode of nozzle feeding. This allows an increase in the gas pressure in the stagnation zone (inlet pressure) up to 15 bar. The current of the clusters with an energy of 20 keV is 20 µA; the maximal current density is 3 µA/cm². The mass spectra of the argon clusters formed at different pressures and electron ionization energy are studied by time-of-flight spectroscopy. The inlet pressure dependence of the mean cluster size is considered as a function of the condensation parameter Г*. An argon cluster beam is used to smooth the surface of the titanium coating and pressed silicon nanopowder. The roughness of the Ti coating surface decreases from 3.7 to 0.8 nm; the removal of microparticles from the surface is also observed. In the case of the surface of Si, besides the smoothing effect the formation of 100 nm craters is observed.

The diffraction and transition radiation of a nonrelativistic charged particle on a perfectly conducting sphere is described using the method of image charges known from electrostatics. Asymptotic formulas that describe the characteristics of the radiation in the low- and high-frequency regions are constructed. It is shown that this approach in the high-frequency limit can be extended to the case of a relativistic incident particle.