Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques最新文献

A complete mathematical model of the generation of radiation and electromagnetic effects inside crystalline dielectrics and at their surface has been constructed. The case of exposure to powerful flows of soft X-ray radiation is considered. The mathematical model is based on the photon and electron transport equations, kinetic equations for photoelectrons, and semi-classical kinetic equations for secondary charge carriers. The system of equations is closed by self-consistent Maxwell equations. The transport equations consider in detail the processes of the electron-photon cascade. For secondary charge carriers, conduction electrons, and valence band holes, the processes of scattering by phonons are taken into account. A comparison of the results obtained using simpler models with the results of applying the complete mathematical model is provided.

A comparative analysis of radiation-induced defect formation in the gallium and nitrogen sublattices of gallium nitride is conducted under irradiation by 15-MeV protons and 0.9-MeV electrons. Numerical modeling using the SRIM software is performed for proton deceleration, while analytical calculations are applied for electrons. The analysis shows that, under proton irradiation, the total vacancy-generation rate in the gallium sublattice η_FP(Ga) is approximately 560 cm^–1, while in the nitrogen sublattice, η_FP(N) is approximately 1340 cm^–1. Detailed numerical calculations using the Full Cascade mode indicate that the vacancy-formation rate due to protons in the gallium sublattice is 110 cm^–1, with an additional 450 cm^–1 generated by cascade processes. In the nitrogen sublattice, this disparity is even more pronounced, with 60 cm^–1 attributed to direct proton interaction and 1280 cm^–1 to cascade processes. Under electron irradiation, the vacancy-generation rate in the gallium sublattice η_FP(Ga) is approximately 4.7 cm^–1, while in the nitrogen sublattice, η_FP(N) is approximately 2.0 cm^–1. For the experimental study of radiation-induced defects in n-GaN, which create deep levels and compensate for the material’s conductivity, the forward current–voltage characteristics of Schottky diodes based on n-GaN are recorded. The analysis demonstrates that the charge-carrier removal rates in n-GaN are 0.47 cm^–1 under electron irradiation and 150 cm^–1 under proton irradiation. A comparison of the calculated and experimental parameters of radiation-induced defect formation provides insights into the compensation mechanism and the radiation-induced defects responsible for this process.

The study examines the electrophysical properties of thin tungsten films deposited by magnetron sputtering, focusing on their thickness, substrate material, phase composition, and structure. The observed patterns indicate the polycrystalline nature of the films, the presence of two tungsten phases, and the isotropy of the magneto-optical properties of thin cobalt films deposited onto tungsten. The dependence of the resistivity on the thickness of the tungsten films and the substrate material is investigated both experimentally and theoretically, demonstrating the dominant contribution of charge-carrier transport across crystallite boundaries.

Plasma surfacing with a thickness of 4–5 mm (argon-plasma-forming gas) was carried out in a protective alloying atmosphere of nitrogen using a non-current-carrying filler flux-cored wire PP-R2M9. Using methods of modern physical materials science, the structural-phase states, microhardness, and tribological properties of surfacing high-speed steel R2M9 on medium-carbon steel 30KhGSA were studied. It has been established that the deposited layer is characterized by the presence of a carbide frame. The main phases of the deposited layer are a solid solution based on α-iron (63 wt %) and carbides of complex composition Me₆C, Me₂₃C₆, and Me₇C₃ (34 wt %). The γ-iron based solid solution is present in a small amount (3 wt %). Carbides of the Me₆C type, which are the main carbide phase, are localized at the boundaries and in the bulk of α-phase grains, while molybdenum carbide particles of the Mo₂C composition are found only in the bulk of the grains. At the junctions of α-phase grains, plastic eutectic grains enriched in atoms of iron, molybdenum, tungsten, and carbon are observed. The microhardness of the deposited layer varies across the cross section from 6.6 to 5.2 GPa, the wear parameter is 1.5 × 10^–5 mm³/(N m), the friction coefficient is 0.57, and the scalar density of randomly distributed dislocations is 7.6 × 10¹⁰ cm^–2.

The study presents the results of the surface hardening of 45- and U10-grade steel samples through complex saturation with boron and copper, followed by electron-beam treatment using a plasma-cathode source. This approach aims to enhance several physical and mechanical properties of boride layers, particularly their plasticity and wear resistance. A comparative analysis is conducted on the structure of the diffusion layer after borocoppering and subsequent modification of this layer by electron-beam treatment. The morphology of the diffusion layer is examined, and its microhardness, elemental composition, and phase composition are investigated. The plasticity of the resulting diffusion layers is evaluated both before and after electron-beam treatment.

The influence of melt meniscus length on the velocity caused by Marangoni convection during noncontact crystal growth has been studied using Te-doped GaSb single crystal grown under microgravity conditions.

The diffusion of chromium from the surface was studied in a polycrystalline Zr–1 wt % Nb alloy under conditions of isothermal diffusion annealing and irradiation with a pulsed electron beam in the temperature range of (0.3–0.4) of the zirconium melting temperature using the high-frequency glow discharge optical emission spectrometry methods. It has been established that the deposition of a chromium film on the surface of the Zr–1 wt % Nb alloy by reactive magnetron sputtering of a target leads to the formation of a zone of mutual penetration of chromium and zirconium. In this case, the grain sizes, as well as the sizes and distribution of particles of the β-Nb phase in the Zr–1 wt % Nb alloy, do not change. Isothermal diffusion annealing and irradiation with a pulsed electron beam result in an increase in the width of the zone of mutual penetration of chromium and zirconium compared to the state after deposition of a chromium film on the alloy surface. A comparative assessment of the chromium diffusion parameter sD_b (s is the segregation coefficient, and D_b is the grain boundary diffusion coefficient) under conditions of isothermal diffusion annealing and irradiation with a pulsed electron beam using the Whipple-Le-Clair equation with a grain boundary width of 0.5 nm was carried out. It has been shown that under conditions of simultaneous exposure to temperature and irradiation with a pulsed electron beam the sD_b parameter increases and the activation energy of grain-boundary diffusion of chromium in the Zr–1 wt % Nb alloy decreases in the near-surface layer of the alloy.

A system of automated software and methodological support SPAAR XRD is developed to process sets of diffraction patterns obtained from synchrotron-radiation sources, enabling analysis of the phase composition and structural parameters of materials. This system incorporates a range of methods and software tools for both the 3D and 2D visualization of diffraction patterns, selection of informative patterns, cluster X‑ray phase identification, and multireflection quantitative X-ray phase analysis using the reference-intensity-ratio method. It also calculates the sizes of coherent-scattering regions employing the simplified Scherrer method. The paper presents results from using this system to analyze a series of diffraction patterns collected during two in situ experiments conducted with a vacuum electron–ion–plasma installation developed at the Tomsk Center of Competence in Beam-Plasma Engineering and Synchrotron Research, Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences. The study examines the high-temperature phase transition between the compounds YbaCo₄O_8.4 and YbaCo₄O₇ over the temperature range of 300–460°C. It also investigates the phase-formation process in multilayer Y–Al–O coatings, which are formed through the alternate deposition of Y and Al on a WC8 alloy substrate in an argon–oxygen environment at 350°C.

It has been established by X-ray photoelectron spectroscopy that the oxidation of thin ruthenium films in oxygen plasma with the addition of 5% inert gases (Ar or Kr) occurs to form an oxide layer of RuO₂. With an increase in ion energy from 20 to 140 eV, the oxygen content in the near-surface layer was found to increase from 60 to 70 at %. The Ru etching rate also increased several times. Such a symbate dependence is explained by the fact that ion bombardment of the surface stimulates not only the removal of weakly bound metal oxides on the surface but also accelerates their formation on the surface. The limiting stage of etching is the removal of low-volatile metal oxides. The shift of the Ru3d doublet peaks, the change in their relative intensity depending on the ion energy, and the presence of an oxygen-enriched layer on the RuO₂ surface indicate that RuO₃ oxide can be formed on the surface during plasma treatment.

Magnesium crystals and their alloys with barium are studied in a multifunctional ultra-high vacuum installation using Auger and photoelectron spectroscopy. Krypton and xenon resonance lamps are used as radiation sources in the vacuum-ultraviolet region. The energy distributions of photoelectrons N(E) and spectral dependences of the quantum yield of photoelectron emission before and after heating magnesium and magnesium–barium alloy are studied. The contribution of surface states and bands formed by magnesium and barium atoms is analyzed. As a result of comparing the photoelectron spectra of magnesium and magnesium–barium alloy obtained at hν = 8.4 and 10 eV, it is found that the electronic structure contains maxima at 0.6–0.7, 1.1–1.2, and 1.5–1.6 eV below the Fermi level caused by the density of electronic states of magnesium and barium. After annealing the magnesium–barium alloy with a volume concentration of barium atoms of 1% at a temperature of 350–400°C, the segregation and thermal diffusion of barium atoms in the alloy surface layers are observed. For the first time, the chemical shifts of the magnesium Auger peaks are established as the concentration of barium atoms in the alloy surface region increases. They are related to the formation of intermetallic compounds with different stoichiometric compositions. It is shown that in the photon-energy range of 5 eV, the quantum yield of photoelectron emission of the alloy is almost an order of magnitude greater than that of pure magnesium. The results are discussed on the basis of published theoretical calculations, in which the magnesium densities of states of magnesium–barium model structures are used.