Vol 12, No 5 (2018)

Using the data of X-ray phase analysis, optical spectroscopy, and scanning electron microscopy of YAG:Ce luminophores, the main types of interactions in complex systems formed by a light-emitting diode luminophore and halide fluxing agents are determined, which cause intense luminescence in the ultraviolet region.

The dynamics of the adsorption and evolution of fluorinated C₆₀F₁₈ fullerene molecules on the Cu(001) surface are studied by real-time ultra-high vacuum scanning tunneling microscopy. Fluorinated fullerene molecules are shown to decompose with time on the Cu(001) surface transforming to C₆₀ molecules. The decay rate depends on the initial molecular coverage. The rapid decay of fluorinated fullerene molecules is observed when the coverage is no higher than 0.2 single layers. As a result, two-dimensional islands consisting of pure C₆₀ molecules are formed on the Cu(001) surface. 2D islands consisting of fluorinated fullerene molecules are formed when the initial molecular coverage is higher than 0.5 single layers. The molecules inside these islands also tend to decompose with time. It is found experimentally that fluorine atoms are removed completely from the initial C₆₀F₁₈ molecules adsorbed on the Cu(001) surface after 250 h when the initial molecular coverage is 0.6 single layers.

The morphology of sphalerite, galena, and chalcopyrite surfaces and the features of potassium butyl xanthate (PBX) adsorption on them under conditions of preliminary mineral treatment with water electrolysis products are studied using atomic-force microscopy and diffuse reflectance IR (infrared) Fourier spectroscopy. It is revealed that practically all types of treatment with electrochemically modified water (the product of non-diafragm treatment, anolyte, and catholyte) coarsens the surface relief of the minerals due to the formation of surface aggregates with different sizes. On the contrary, after chalcopyrite is treated with anolyte, its surface relief become smoother. It is found that water electrolysis products differently affect the chemical and physical types of PBX adsorption on the surface of the minerals under investigation. The performed experiments indicate that a complex of atomic-force microscopy and IR Fourier spectroscopy techniques is an efficient ex situ approach for monitoring the surface state of sulfide minerals and the direct study of PBX adsorption products.

50 keV ⁶⁴Zn⁺ ions to a dose of 5 × 10¹⁶ cm^–2 are implanted into substrates of single-crystal n-type silicon. Then the samples are irradiated at room temperature with 167 MeV ¹³²Xe²⁶⁺ ions with a fluence ranging from 1 ×10¹² up to 5 × 10¹⁴ cm^–2. Changes in the structure and properties on the sample surface and in its body are studied by scanning electron microscopy, energy dispersive microanalysis, atomic force microscopy, time-of-flight secondary ion mass spectrometry, and photoluminescence.

The results of theoretical and experimental studies of the influence of Ba-atom implantation and the presence of an oxide film on the Si-surface sputtering coefficient under ion bombardment are presented. It is shown that, in the dose range of D = 10¹⁴–5 × 10¹⁵ cm^—2, the Si sputtering coefficient increases linearly, then this increase decelerates, and is almost constant, starting from 10¹⁶ cm^–2. In the range of D = 5 × 10¹⁵–5 × 10¹⁶ cm^—2, the Ba sputtering coefficient increases sharply, which is explained by an increase in the Ba concentration in the surface layer during the ion bombardment process.

Analysis of the known techniques for simulating the surface microtopography indicates a substantial difference between the surface reliefs resultant from their application and real ones. In order to more accurately determine the surface microrelief, a numerical method is proposed making it possible to create a 3D surface roughness model ensuring accurate repetition of the relief of a real prototype. In turn, the resulting model geometry of the surface enables us to determine real actual contact areas and the relative positions of the protuberances and cavities of contacting surfaces. It is proved that the proposed method has advantages over known empirical dependences.

Monte-Carlo computer simulation is employed to investigate the surface phase transition (PT) in the 3D semibounded antiferromagnetic Ising model. Simulation is performed at different ratios of exchange integrals on the system surface and in its bulk. The dependence between the PT temperature and the distance to the surface is studied. When the ratio of exchange integrals is less than 1.38, the PT temperature is found to increase with distance from the surface. A comparison with the results of a real experiment is carried out. The simulation results are demonstrated to be in qualitative and quantitative agreement with experimental data.

The degree of enantiomorphic excess (average chirality 〈Γ〉)in bulk polycrystalline Fe_1–xCo_xSi samples with a cobalt concentration of x = 0.10, 0.15, 0.20, 0.25, 0.30, and 0.50 is studied. Polycrystals are synthesized by melting the initial high-purity components. Surface examination of the samples showed that they are composed of acicular coaxially oriented crystallites with an average volume of ~2 mm³. The magnetic chirality γ, which is directly related to the crystallographic chirality Γ as γ =–Γ, is measured using small-angle polarized neutron diffraction. It is established that the average chirality of polycrystals 〈γ〉 is independent of the Co concentration within the statistical precision of the number of crystallites in the samples used in the experiment. The chirality of individual polycrystallites is distinct from zero and sometimes reaches 10–20%, being determined by the total number of crystallites in a sample (~100). The measurement error of the average chirality 〈γ〉 is determined by neutron scattering statistics and does not exceed 1%.

The main advantages and problems of maskless X-ray lithography (MXRL) are discussed. Consideration is given to two concepts of lithography in which the chip of a microoptical electromechanical system (MOEMS) of micromirrors and a microfocus X-ray tube chip with a “breakthrough” thin-film target are used as dynamic masks. Each of them can occupy its own niche in a research area or in the mass production of microchips. A description of the project of a MXRL facility (demonstrator of technologies), which is based on the concept of MOEMS, developed at the Institute for Physics of Microstructures, Russian Academy of Sciences, is presented for the first time.

A method providing more than a tenfold improvement in the precision of exposure field alignment in electron-beam lithography is proposed. The method uses a scanning electron microscope with a standard mechanical positioning system and alignment markers produced by contact photolithography. Bragg–Fresnel lens (1–3–5 orders) with a tenfold decrease in the error of exposure field alignment through the use of mechanical stages are created via this technique.

Comprehensive studies of the volume (structural, optical, electrophysical) and surface (acid-base, adsorption) properties of solid solutions and binary components of the CdS–CdTe and CdSe–CdTe systems are carried out. The regularities in the changes of these properties with a variation in the composition and the parallels between the patterns within each system and under their comparison are established. The leading influence of the common binary component, cadmium telluride, on the properties of solid solutions of both systems is revealed. The possibility of predicting the surface activity of these new materials with respect to gases of different electronic natures is shown on the basis of the results of less labor-intensive studies of the bulk physical and chemical properties (in comparison with direct studies of the surface characteristics, i.e., acid-base and adsorption characteristics). Practical recommendations on using the obtained materials in corresponding sensors are made.

The geometric characteristics of the supersonic nozzle of a plasmatron intended for vacuum plasma sputtering, which creates a Prandtl–Meyer expansion fan, are estimated. The nozzle facilitates nanoparticle condensation from the vapor phase of the sputtered material due its cooling in the vicinity of the nozzle cross section rotated by 6° and 27°. During the process of sputtering, a coating containing mainly large-scale particles and their fragments and a film consisting of nanoparticles are formed if the central part of the nozzle and its peripheral regions pass over the sample, respectively. Investigation into the surface structure of a HfO₂–9% Y₂O₃ coating 30 μm thick indicates the existence of deformed particles and nanostructured regions in the form of thin film fragments.

The low-energy electron irradiation effect on the defect structure on epitaxial laterally overgrown (ELOG) films and thick GaN crystals grown via the hydride epitaxy method is studied using a scanning electron microscope by the induced-current and cathodoluminescence methods. Electron-beam irradiation is carried out at room temperature. In this case, the electron-beam irradiation effect on dislocation segments located in the basal plane is studied in ELOG GaN films. At the same time, dislocations are introduced into GaN crystals by indentation at room temperature. It is found that the behavior of growth dislocations and those introduced by indentation is different under electron-beam irradiation.

The paper considers an approach to the construction and study of the emission (volt-ampere) characteristics of a system with a field electron cathode by regression analysis methods. A three-parameter model of the field electron emission signal is proposed. Estimates of the parameters of the current dependence on voltage are obtained in the framework of mathematical modeling. Estimation is carried out using a quadratic functional for linear and nonlinear models. Model selection should be determined by the analysis of so-called “regression residuals”, which are influenced by measurement errors. The validity of the application of both the linear and weighted nonlinear least-squares methods is shown as a result of mathematical modeling.

The influence of charged sapphire steps on gold, ZnO, and CdTe nanoislands formed on the surface of Al₂O₃ under vacuum condensation is discussed. Electrically active surface steps are interpreted as a particular case of electrical boundaries existing on dielectric crystal surfaces. The interaction between an uncharged dome-shaped nanoisland and a uniformly charged step is estimated.

The deuterium release from reduced activation Eurofer steel samples is investigated by measuring the re-emission directly during ion irradiation and via thermal desorption spectroscopy without contact with air. A part of the experiments are carried out using a sample previously subjected to high-power pulsed thermal action using the QSPA-T setup, Troitsk Institute of Innovative and Thermonuclear Research. Subsequent irradiation is performed using a 5-keV D₃⁺ ion beam to a fluence of up to 10²¹ m^–2 at room temperature. In all cases, a major part of the implanted deuterium is released from the sample already at the irradiation stage. A significant part of the deuterium also desorbs in the interval between irradiation and spectroscopic measurements. Deuterium re-emission from damaged samples reaches a maximum value more slowly than that from undamaged ones, and deuterium release during holding is more intense. This can be explained by the structure of the damages caused by the heat flux: the hydrogen-trap concentration grows in the material, and the surface area participating in desorption increases.

A stand for the irradiation of electronic integrated circuits is developed at the proton beam of the linear accelerator of the Institute for Nuclear Research, Russian Academy of Sciences. Estimation of secondary neutron fluxes in the experimental hall and in the surrounding medium outside the external shielding of the accelerator is performed. The issue of the impact of albedo protons and neutrons from the beam trap on the irradiated object is considered. The activation and cooling of the stand elements and the irradiated object as well as the dose rate are calculated. The data obtained allow safe operating conditions of the stand and optimal modes of irradiation to be selected. The calculations were carried out by the Monte Carlo method using the SHIELD hadron transport code for proton-beam parameters which are maximal at this time: energy of 209 MeV, current of 1 μA.