Vol 11, No 1 (2017)

A periodic magnetic Fe/Co multilayer nanostructure is investigated via neutron reflectometry with the help of the time-of-flight technique and the obtained results are presented. The experimental and calculated reflection coefficients of a neutron beam depending on the transmitted pulse are discussed for several magnetic fields and both beam spin components. It is experimentally established and confirmed by calculations that, for the first Bragg peaks and both beam spin components, the reflection coefficients are almost equal to each other and depend slightly on magnetic field.

The dynamic theory of the coherent X-ray radiation of a divergent beam of relativistic electrons generated in a single-crystal wafer under conditions of the multiple scattering of incident particles is developed. Radiation cross sections are averaged over the divergent beam of rectilinear trajectories of electrons. Expressions describing the spectral-angular characteristics of parametric X-ray radiation and diffracted transition radiation under conditions of multiple scattering are obtained. Conditions under which the contribution of diffracted brehmsstrahlung can be disregarded are shown, and the spectral-angular characteristics of parametric X-ray radiation and diffracted transition radiation are calculated numerically for such conditions.

Titanium dioxide nanotubes (NTs) built from various initial 2D models of TiO2 (a promising catalyst for water splitting) are investigated via density functional theory using the B3LYP hybrid exchange-correlation functional in the localized basis set of a linear combination of atomic orbitals. For TiO₂ NTs (eight different types of morphology) created from four initial 2D structures, full geometry optimization is performed and the main energy parameters, such as the band gap width, energy positions of the valence band top and the conduction band bottom, and NT formation and strain energy, are calculated. Analysis of the NT strain and formation energies enables us to choose their most stable configuration, which can further be employed to simulate NTs doped with impurity atoms capable of serving as efficient centers for the photocatalytic dissociation of water molecules.

Ensembles of metal nanowires are prepared by the template method. The influence of electrodeposition conditions on the properties of the obtained samples is studied for some metals and alloys. It is shown that the observed change in the electrodeposition rate during electrolysis can be related to a change in the electrode potential as a result of an increase in the gradient potential in the near-electrode solution region and to diffusion limitations. A number of specific features of the deposition of iron, iron–cobalt alloy, and iron–nickel alloy are revealed (in particular, the dependence of the elemental composition of the obtained wires on the electrodeposition conditions). Both the topography of the nanowires and their stability are investigated by electron microscopy. It is found that the nanowire form does not always correspond to the form of growth pores. Nanowires exhibit rather high stability in alkali solutions and low stability in acid solutions.

The systematic studies of the electronic state of surface layers in organic semiconductor (DOEO)₄[HgBr₄] · TCE by X-ray photoelectron spectroscopy and UV photoelectron spectroscopy are performed. At temperatures below 50–70 K, a transition to the antiferromagnetic state is observed in inclusions having a different structure compared to the crystal bulk. According to transmission electron microscopy, there are two types of antiferromagnetic inclusions in the samples, with sizes of 2–5 and 100–400 nm. The contributions of antiferromagnetic inclusions and the spins of localized and free charge carriers (holes) to the total magnetic moment of the crystal are separated.

The possibilities of interpreting the secondary-electron energy spectra and recording the X-ray photoemission of single-crystal silicon samples are examined. Detected shifts in the energy-spectrum extremum, as well as its height, and the entire energy-distribution form for different types of implanted and annealed Si samples, indicate the degree of ordering of surface atoms. The possibilities of employing the Friedel- oscillation model are discussed.

With the development of electron microscopy-based porosity measurement techniques, it is possible to devise new oil and gas reservoir rock classification schemes that would take the geometrical features of the pore space into account. This is associated with the fact that the structure of the pore space of reservoir rocks has a significant effect on the recovery of hydrocarbons upon reservoir processing. For several years, we have carried out microstructural studies of rocks from the productive strata of various fields using cathodoluminescence scanning electron microscopy (SEM) and porometric software for the analysis of SEM images. The investigations show that it is possible to classify reservoirs by the connectivity of pores and pore channels in reservoir rocks.

The results of investigations of the structure of BaTiO₃ under thermobaric effects at constant volume are presented. The pressure and temperature values of the structural phase transition from the tetragonal ferroelectric phase to the cubic paraelectric phase at constant volume are determined. The temperature and pressure coefficients for the various phases of BaTiO₃ are found. The Birch–Murnaghan equations of state are calculated and the parameters B₀ and B′ are established.

The classical phenomenological Londons’ theory of superconductivity is analyzed in detail. The incorrectness of the derivation of the basic system of equations and the lack of evidentiary support of the assumption concerning the irrotational fluid flow of superconducting electrons are shown. It is concluded that, for superconductors, it is impossible to determine the vector of the magnetic-field strength unambiguously, since it is unclear how to divide the superconducting current into the conduction current and the magnetizing current. The concentration of electrons is refined within the framework of the Gorter–Casimir model of a two-component electron fluid in superconductors with the Drude–Lorentz–Sommerfeld theory taken into account. The temperature dependence of the critical magnetic field is calculated and compared with the classical result. It is shown that this parameter can be changed within a rather wide range within the framework of accuracy of the experimental data. Based on results obtained for constant currents in materials with a high conductivity, a hypothesis about identification of the thickness of the thin layer in which surface currents flow with a depth of penetration of the magnetic field into the material is proposed.

The evolution of a Saccharomyces cerevisiae suspension deposited onto the surface of silicon is investigated. Evolution of the yeast is caused by the effect of a weak stationary magnetic field (B = 0.17 T) and low-energy (E = 8 keV) low-dose (D = 10⁴ Gy) X-ray radiation. It is found that the magnetic and X-ray treatment of the yeast suspension leads to ordering of the cell structures. It is suggested that one reason for this ordering is the presence of electric charges in the cells and on the surface of the silicon crystals exposed to magnetic and X-ray treatment.

Data on X-ray diffraction in lanthanum diphthalocyanine pyrolysates synthesized at temperatures of 800–1800°С demonstrate the formation of an amorphous carbon phase with embedded lanthanum atoms. Low-temperature pyrolysis (800–900°С) creates layered carbon structures. Due to annealing at 1000°С, carbon integrates into globules whose number of atoms is m ~ 100. Such structures with gyration radii of R_g ~ 0.4–0.5 nm on the order of the precursor molecule size are synthesized in the temperature range of 1000–1800°С, and are stable in terms of size and mass. In this case, their density approaches that of graphite.

The C, Cu and W element profiles in films deposited using a plasma focus facility are studied by the Rutherford backscattering of 2-MeV He⁺ ions. The films are deposited onto glass substrates in Ar plasmaforming gas. The element profiles are found to depend significantly on the kinetic energy of particles. The penetration depth of particles with the velocity ~10⁵ m/s is about 1.5 μm. The corresponding element profiles showing the distribution of elements over the thickness of the glass are non-linear. For each element, the maximum layer depth is observed under the glass surface. The formation of Cu, W and C layers under the glass surface and their overlapping is a feature of films deposited using the plasma focus facility. Such an arrangement of layers evidences the significant difference between this method of film deposition and conventional techniques at low rates of atom deposition, as well as diffusion-based methods. The obtained films are found to have dielectric properties.

Electron backscatter diffraction is used to determine the influence of mechanical polishing on the surface state of a two-layer structure made from diamond. It is found that the process of polishing does not lead to significant degradation of the surface, while the thickness of the amorphous layer formed due to polishing does not exceed a few atomic layers.

Pyrolytic graphite films prepared by means of microsplitting are studied. In the samples, the alternation of pentagonal and hexagonal symmetry planes is revealed. These graphite crystal states can be classified as mesoscopic fullerene-like structures.

The effect of Co⁺-ion implantation on the surface composition and the depth distribution profiles of atoms in a Si–Cu (100) heterostructure is investigated. After heating of the ion-implanted sample, a 50–60 Å thick CoSi₂ film is formed. It is revealed that after ion implantation the penetration depth of Cu atoms in Si becomes twice as large.

A fragment of a text written in red ink is scanned at the X-ray fluorescence analysis station of the Kurchatov synchrotron radiation facility; the element distribution in the scanned region is obtained. The possibility of imaging and reading text fragments using synchrotron radiation is proved.

Two independent methods based on a neutron detector with He-3 counters and a CR-39 track detector are used to measure neutron and proton emissions from the nuclear reaction in samples of deuterated structures of textured CVD (chemical vapor deposited) diamond, palladium, and zirconium irradiated with X-ray quantum beams. It is demonstrated that, in solid-state deuterated targets, the DD reaction can be stimulated by X-ray quanta with energies of 20−30 keV.

The influence of corona-discharge treatment on the physical properties and structural state of superdispersed magnetite particles is investigated. It is ascertained that corona-discharge treatment can lead to the formation of polymorphous modifications.

We investigate the possibility of the generation of arrays of single-crystal islands with small angular dispersion in order to use them as active media for solving the problems of controlling the parameters of X-ray beams. Using the example of a three-layer structure of substrate–adhesive–single-crystal wafer, we experimentally demonstrate the possibility of controlling the profile of diffractive elements by changing its temperature. It is revealed that the main reason for island misorientation is shrinkage of the adhesive material upon its solidification. Another reason for misorientation is softening the adhesive, which occurs upon plasma-chemical etching of the wafer. These effects can be eliminated by changing the temperature of attaching the wafer to the substrate surface and by using a nonsoftening adhesive. The temperature of attaching a single-crystal wafer to the substrate is calculated from the shrinkage coefficients of the adhesive and the thermal- expansion coefficients of the components of the structure.

The principles of construction and the components of a model of X-ray fluorescence signal generation are considered in this paper. It is shown that the developed model describes the X-ray spectra of various materials rather well. Issues with choosing the optimal parameters of measurements in the quantitative X-ray fluorescence analysis of individual samples using the constructed models are discussed.

Carbon crystallites in separate vertically oriented nanopillars grown on the surface of a substrate by low-temperature plasma-enhanced chemical-vapor deposition (LTPECVD) without a catalyst are studied by transmission electron microscopy (TEM) and electron diffraction. Thin planar lamellae are manufactured from the half-height section of an array of nanopillars using a focused ion beam. It is established that the crystallites in an amorphous environment are constructed from fragments of basal planes (002), have no well-distinguished boundaries, and their size is generally 1–2 nm. It is shown that the fraction of crystallites in the total volume of the material of nanopillars gradually grows, and the average distance between the basal planes decreases after annealing at temperatures of 250 and 700°C.

The method of titanium-hydride pellet (THP) modification by the surface deposition of metal titanium with the ion–plasma vacuum magnetron sputtering is described in this paper. The surface microstructure of the initial samples is compared with that of samples with the deposited coating. Found to be practically the same along the surface, the thickness of the deposited layer equals approximately 275 nm. The interface between the deposited titanium and THP is visible over the entire recorded region. The spectra of the thermal desorption of hydrogen from the initial and titanium-coated samples are presented. The coating is shown to significantly increase the temperature of THP dissociation.

Copper nanotubes are electrochemically synthesized using ion-track polyethylene terephthalate templates. The structure and morphology of the nanotubes constructed under different synthesis conditions are studied with the assistance of scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis, and the manometric gas-permeability method. The dependence of structural features on the electrodeposition potential is established.