Vol 13, No 1 (2019)

A set of multilayer X-ray mirrors for an upgraded version of the double-mirror monochromator installed on the VEPP-5 synchrotron of the Budker Institute of Nuclear Physics is fabricated, its constituent parts are optimized, and its X-ray optical characteristics are studied. Due to the use of seven subbands, for each of which an optimal pair of materials is chosen, the mirror set ensures high reflection coefficients—ranging from 10 to 75%— for a wide range of photon energies from 80 to 3000 eV and wavelengths from 0.413 to 15.48 nm. The principles of optimization of material pairs are reported. For the first time, multilayer mirrors based on the W/Be pair of materials are fabricated and studied.

The initial stages of the adsorption of fluorinated fullerenes C₆₀F₁₈ at the Si(111)-7 × 7, Si(001)-2 × 1, and Cu(001)-1 × 1 surfaces are studied by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy in ultra-high vacuum. By combining STM imaging of individual molecules and ab initio calculations of the total energy, we demonstrate that polar C₆₀F₁₈ molecules interact with the surface with their fluorine atoms facing toward the surface. Molecules of the investigated fluorofullerenes enable surface modification at the nanoscale by local etching. By analyzing the experimental STM images and their computer-simulated counterparts, we show that the adsorbed fullerene molecules give up their F atoms to the Si surface. The binding energy between the fluorine atom and the Si surface is almost twice as high as that between the fluorine atom and the C₆₀ molecule. The rate of disintegration of the fluorofullerene molecules adsorbed at the Cu(001) surface depends on the initial surface coverage. Initially, adsorbed C₆₀F₁₈ molecules lose some of their fluoride atoms, giving rise to two-dimensional islands consisting of C₆₀ and C₆₀F_n molecules.

The time dynamics of the spatial distribution of electrons locally injected from the probe of an atomic force microscope into thin (less than 10 nm) ZrO₂(Y) films with embedded Au nanoparticles on Si substrates is studied via Kelvin probe force microscopy. The profiles of the film surface potential induced by the injection of a countable number (several tens) of electrons into Au nanoparticles, as a function of the time elapsed after injection, are measured and analyzed.

It is shown that changing the angle of deposition of a coating onto a nanostructured substrate with an asymmetric profile (high-frequency blazed grating) has an effect both on smoothing of the groove profile of a multilayer grating (its symmetrization and/ or a decrease in its depth) and induces a significant displacement of the groove-profile maximum either to the left or to the right relative to the substrate profile. It is established that the displacement of interlayer boundaries is a linear function of the angle of deposition of the material and the change in the profile depth is a nonlinear function. By controlling the orientation of the source of the depositing material with respect to the groove’s working facet, controlled deformation of the profile can be attained in the nonlinear continuous growth equation. At a certain orientation of the source and taking into account realistic profile boundaries, the maximum diffraction efficiency of a grating at a given order of the spectrum is predicted to be higher than the similar efficiency of a grating with perfect triangular boundaries positioned strictly vertically one above the other. The optimal values of the boundary displacement, which are found from simulating the growth of a W/B₄C 2500/mm grating with a blaze angle of 1.76° and an antiblaze angle of 20°, make it possible to achieve a diffraction efficiency of about 0.82−0.9 relative to the reflection of a multilayer mirror optimized for a wavelength of 1.3 nm. The maximum achievable efficiency for steeper angles of a non-working facet is somewhat higher.

The reflection spectra and changes in them are analyzed comparatively after the irradiation of ZnO micropowders and nanopowders with protons and electrons with an energy of 100 keV. It is established that the reflectance and the radiation resistance of ZnO micropowders (400‒800 nm) is higher than that of nanopowders (30‒50 nm) to the given types of exposure.

Structural investigations of solid solutions of BaFe_12 – xIn_xO₁₉ barium ferrites partially substituted with indium ions (x = 0.1–1.2) are carried out via the neutron diffraction method. Experimental investigations of ceramic samples are performed at room temperature using a high-resolution neutron diffractometer that allows precise information about changes in the crystal and magnetic structures, as well as microstructural parameters, to be obtained. Refinement of the crystal structure of the composition BaFe_12 – xIn_xO₁₉ is carried out in the framework of two space groups P6₃/mmc and Р6₃mc. Solid solutions of barium ferrites retain the hexagonal crystal-structure type in the entire investigated concentration range. Their ferrimagnetic structure is well described by Gorter’s model where magnetic moments are ordered along the c axis. Spontaneous polarization is revealed in barium hexaferrites partially substituted with indium ions. The total magnetic moment per formula unit decreases as the amount of diamagnetic In ions is increased. An increase in microstrains in the crystallites with increasing amount of In ions is explained by increasing disorder of the system because of the statistical distribution of diamagnetic ions in magnetic sublattices.

The phase and structural transformations that Pd–Ru(7 at %) solid solution thin films undergo during thermal oxidation in oxygen in the temperature range 570–1070 K are studied by transmission electron microscopy, high-energy electron diffraction, and reflection high-energy electron diffraction. With increasing oxidation temperature, the phase composition is found to change in the order: Pd–Ru(7 at %) solid solution → Pd–Ru(7 at %) + PdO + RuO₂ → PdO + RuO₂ → PdO–RuO₂ solid solution. We show that the complete oxidation of Pd–Ru(7 at.%) thin films to form single-phase films of the PdO–RuO₂ solid solution takes place at a temperature of 100 K higher compared to pure palladium films. The resistance sensor response of the prepared PdO−RuO₂ oxide films to ozone in air is studied for the first time. The results suggest that this is a promising material for use in gas-sensing applications.

During the operation of lasers based on an AlGaN/InGaN/GaN structure with electron-beam- and optical pumping, a gradual decrease in the output power is observed. In the first minutes of the operation of optical pumping lasers, a certain increase (by 5–10%) in the output power with a successive gradual decrease can be observed. Upon sample cooling, the rate of output-power degradation decreases. A decrease in the output power during operation of the laser is accompanied by changes in the emission spectrum—the line maximum shifts to the short-wavelength region and additional maxima appear. The observed effects can be explained both by the passivation of the initial defects and the diffusion of atoms of the structure during laser operation. The changes in the emission spectra are apparently associated with competition between two different generation channels.

Small-angle X-ray scattering (SAXS) is used to characterize the vesicular structure of the phospholipid transport nanosystem (PTNS) at PTNS concentrations in water of 25, 31.25, and 37.5% (w/w). The average vesicle radius, size polydispersity, bilayer thickness, and internal structure are determined from the experiment using two models for the photon scattering density distribution. Two independent methods are used to calculate the SAXS spectra: the form factor of a heterogeneous spherical shell and the method of separated form factors. The two methods for calculating the spectra and two models for description of the internal structure of the lipid bilayer provide identical results, which demonstrate a decrease in the vesicle radius, thickness of the bilayer, and thickness of the hydrocarbon-chain region upon an increase in the maltose concentration in water. It is shown that a decrease in the lipid bilayer thickness upon an increase in the maltose concentration is caused by interdigitation of the hydrocarbon chains. The hydrophobic volume of one vesicle suitable for water-insoluble drugs is shown to have a maximum value of 14.55 × 10⁶ ų at a PTNS concentration in water of 25%. Increasing the PTNS concentration in water up to 37.5% leads to a decrease in the hydrophobic volume to 6.16 × 10⁶ ų.

The methods and results of electron microscopic study of the microstructure of siliceous-carbonate rocks of the domanikoid type are shown. For this purpose, both standard methods for studying the surface of sample chips and a polished surface for microprobe studies and a specially developed method for cathode luminescence study of the pore space are used. Regularities in the catagenetic transformation of Domanik deposits are studied at the microscopic level by electron microscopy. The performed studies show that subcapillary porosity in them is formed only in fractal-cluster areas of origin of secondary (authigenic and syngenetic) carbonatization. This study substantiates the fractal-cluster approach to the probabilistic forecasting of areas of secondary carbonatization and oil-saturated pore volumes.

The formation of radiation defects in the silicon-carbide sublattice under irradiation with 15-MeV protons and 0.9-MeV electron is analyzed. Numerical simulation is carried out, and histograms of the distribution of the energy transferred to carbon recoil atoms are obtained. Two energy ranges are considered when analyzing the histograms. Single isolated Frenkel pairs with closely located components are produced in the low-energy range. The recoil atom energy is sufficient to produce a displacement cascade in the other range. As the energy of primary knocked-out atoms increases, the average distance between genetically related Frenkel pairs increases, and as a consequence, the fraction of pairs that do not recombine under irradiation increases. The recombination radius of the Frenkel pair in the carbon sublattice is estimated.

The morphology of the metal films deposited onto diamond by the ion-plasma method at a temperature of 600°С under vacuum (10^–2 Pa) are studied by scanning electron microscopy. It is shown that crystalline formations and needle structures are formed on the surface of the films. It is established by X-ray phase analysis that Ni_mTi_n compounds are mainly formed.

Simulation of ion and fast atom motion in the low-current discharge in an argon-mercury mixture used in gas discharge illuminating lamps is performed with the Monte Carlo method. As at the stage of discharge ignition mercury relative content in the mixture is small, only collisions of fast particles with slow argon atoms are taken into account. The energy spectra of the ion and fast atom flows bombarding the cathode surface are calculated. The energy distribution of mercury ions is shown to differ considerably from that found previously from analytical model based on the approximation of mercury ion continuous slowing down in argon. The effective rates of tungsten cathode sputtering by ions and fast atoms are calculated, as well as the flow densities of sputtered atoms, as functions of the reduced electric field strength in the discharge gap. At small mercury content in the mixture of the order of 10^–3, the cathode is found to be sputtered mainly by mercury ions. Their contribution to sputtering process decreases with increasing in the reduced electric field strength and decreasing in the mixture temperature.