No 11 (2023)

The effect of irradiation with hydrogen, helium, nitrogen and neon ions with an average energy of 0.8 keV on the surface morphology under magnetron sputtering of a high-modular carbon fiber made of polyacrylonitrile was studied experimentally. In all cases, a whisker-like relief was formed on the surface. The greatest height of whiskers was obtained under irradiation with nitrogen and neon ions, the lowest height and lower density of whiskers was obtained under irradiation with hydrogen ions. Comparison with irradiation of polyacrylonitrile carbon fiber with noble gas and nitrogen ions with energies of 10–30 keV shows that the whisker-like morphology complements the variety of types of ion-induced fiber surface morphology. The results obtained are discussed within the framework of existing models of formation of ion-induced morphological elements on the surface of graphite-like materials. It is assumed that there is a threshold in the number of radiation displacements created in the surface layer, leading to the observed qualitative difference in ion-induced morphology at low and high energies. The evaluations of the displacement profiles for the case of irradiation with hydrogen ions show several-fold fewer displacements than for other ions, which correlates with the observed differences in whiskering by selected ions and whisker growth factors observed in the experiment performed.

The influence of the free volume on the crystallization processes of Fe₇₈Si₁₃B₉ and Al₈₇Ni₈Gd₅ amorphous alloys was studied by X-ray diffraction. To study the influence of the free volume, two methods of amorphous alloys deformation were carried out: ultrasonic treatment and multiple rolling. After deformation, a protective coating was applied to the amorphous alloys. It is shown that the deposition of a protective coating with a higher vacancy formation energy compared to the vacancy formation energy in the amorphous alloys under study is an effective way to maintain the free volume in the amorphous phase, since it is thermodynamically unfavorable for the free volume to migrate from the amorphous phase into the coating material. Experimental data indicate that the preliminary deformation of amorphous alloys leads to an increase in the amount of free volume. An increase in the amount of free volume and its maintenance by protective coating contributes to a significant crystallization acceleration of Fe₇₈Si₁₃B₉ and Al₈₇Ni₈Gd₅ amorphous alloys. The results obtained expand the existing ideas about the processes of crystallization of amorphous alloys and indicate the possibility of developing materials with different structural characteristics and, consequently, with different physicochemical properties.

Methods were proposed and criteria were established for surface preparation of nanostructured thermoelectric materials for deposition of thin and thick film ohmic contacts. The parameters of the mechanical and chemical methods of thermoelectric material surface treatment before the deposition of contacts were established. The roughness and morphology of the surface of thermoelectric material samples and the films obtained have been studied. Criteria and optimal values of surface roughness of thermoelectric materials were established. The conditions of obtaining thin and thick film contacts were determined. Thin film contacts (thickness up to 300 nm) were obtained by magnetron sputtering of Ni. Thick film contacts were formed by chemical and electrochemical deposition of Ni. The obtained films contained various amounts of Ni. The electrical resistivity of Ni films obtained by chemical deposition was significantly higher than that of Ni films obtained by electrochemical deposition. The specific contact resistance of the metal–thermoelectric material system in the case of deposition of Ni films by magnetron sputtering was the smallest among the considered samples. And in the case of forming contacts by chemical deposition, it is comparable to that for Ni films formed by electrochemical deposition. The adhesion strength of Ni films obtained by various methods has high values exceeding the industry standard for film coatings in microelectronics. All obtained ohmic contacts satisfy the requirements for the construction of the efficient thermoelements by the electrical properties and adhesive strength.

The samples of monocrystalline silicon coated with golden nanolayers were investigated. The samples were obtained by two methods, namely, gold sputtering using Xe⁺ beam with the initial energy of 7 keV and the method of thermal deposition. Preliminary analysis of samples based on the deciphering of energy spectra of reflected protons with an initial energy of 25 keV was performed. By methods of X-ray photoelectron spectroscopy with angular resolution (Angle Resolved XPS) thicknesses of gold coatings on silicon were determined. Analysis of samples using X-ray photoelectron spectroscopy was performed by comparing the intensities of Au 4f and Si 2p maxima measured at different angles of photoelectron detection. The calculations carried out by traditional methods indicate a marked dependence of the calculated gold coating thickness on the angle of sight for the case of monolayer and submonolayer coatings. It is shown that such discrepancy is possible if gold is deposited on silicon in the form of clusters forming islands rather than in the form of a continuous homogeneous coating. The possibility of gold islands moving relative to silicon in the upper silicon layers that have been subjected to proton bombardment at sliding angles to the surface is discussed.

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.

The test results and performance characteristics of an indirectly crycooled superconducting solenoid to be used at the THz spectroscopy experimental station of free-electron laser at the Institute of Nuclear Physics, are presented. The superconducting solenoid with a winding diameter of 102 mm and a length of 0.5 m was designed for a magnetic field of 6.5 T. The warm bore diameter of 80 mm is available for THz spectroscopy experiments. The superconducting wire Cu/NbTi = 1.4 was used. The design implements passive protection methods due to sectioning and secondary connected circuits in case of a sudden quench. The required field uniformity of 0.5% was ensured by using an iron yoke and additional side windings. The cryogenics of the solenoid is based on two Sumitomo HI cryocoolers. The solenoid and iron yoke are cooled by the second stage of the cryocooler via copper links. The manufacturing technology of the solenoid is described in detail. The solenoid was tested in a liquid helium bath and in its own cryostat. Its characteristics meet the requirements of the experimental station. The obtained filed of 7.5 T is greater than the designed one due to overcooling up to 3.6 K. The magnetic field was measured both in a bath cryostat and in a design cryostat; the results corresponded to the design calculations. The solenoid cooling time is 13 days. The quench happened only twice, at 5.6 and 7.5 T.

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.

Beamlines nowadays installed at synchrotron radiation centers typically pose different and sometimes even incompatible requirements to X-ray beams being utilized. Some techniques require minimum attainable beam cross-sections in order to enable microbeam techniques with the sample mapping. To the contrary, relatively broad X-ray beams with the uniform intensity distribution are needed to address problems related to X-ray irradiation-based processing of materials or fabrication of components and devices with X-ray lithography approaches. The present paper describes the concept of a novel beamline named X-Techno proposed for the synchrotron radiation facility SKIF. It would use synchrotron beams as wide as 100 mm in the horizontal plane in different spectral ranges with either out of three experimental chambers to study materials and manufacture micro and nanostructures. The beamline will be specifically suitable for studies of physicochemical properties of materials under intense X-ray irradiation within the spectral range from 2 to 70 keV.