Том 13, № 3 (2019)

We carry out comparative studies of the phase composition, morphology, and hardness of semiconductor legs based on the n-type solid solution Bi₂Te₃−Bi₂Se₃, obtained by hot pressing, after surface modification (mechanical processing and pulsed photon treatment (PPT) with incoherent light). Using shear tests, we determine the adhesion of switching and barrier Mo–Ni layers on the modified surfaces of semiconductor legs. Pulsed photon treatment stimulates local recrystallization of the imperfect layer near the surface of samples of the Bi₂Te₃−Bi₂Se₃ solid solution to a depth of 100−200 nm, which increases the hardness of the surface layers. It is shown that the mechanical polishing and subsequent pulsed photon treatment of thermoelectric legs increases the adhesion of the switching and barrier Mo–Ni layers by 3–4 times, which can contribute to the efficient and stable operation of a thermoelectric generator battery.

The surface layer of a SiO₂/Si structure implanted with Zn⁺ and O⁺ ions and annealed in neutral and inert atmospheres is studied. At first, n-Si(100) silicon plates are oxidized in dry O₂ to achieve an oxide-film thickness of 0.2 μm. Then, at room temperature, they are sequentially implanted with a dose of 5 × 10¹⁶ cm^–2 of 70-keV ⁶⁴Zn⁺ ions and with a dose of 6.1 × 10¹⁶ cm^–2 of 40-keV \(^{{16}}{\text{O}}_{2}^{ + }\) ions. Plate overheating, compared with room temperature, does not exceed 70°C. The samples are isochronously annealed for 1 h in N₂ at a temperature from 400 to 600°C and then in Ar in the range of 700–1000°C with a step of 100°C. After implantation, the crystalline phase Zn(102) is found to form in the SiO₂ film. After annealing at 700°C, Zn is oxidized to form the ZnO phase. Analysis of the diffraction patterns shows the β-Zn₂SiO₄ and Zn_1.95SiO₄ phases to be additionally formed in the samples after annealing at 800°C. After annealing at 900°C and above, the ZnO phase was not detected in the samples.

This work presents the results of the X-ray photoelectron spectroscopy investigation of carbon films obtained by ion-plasma deposition at various plasma compositions. The detailed analysis of X-ray photoelectron spectra makes it possible to determine the structure of the deposited films and the influence of the presence of nitrogen and hydrogen in the plasma on the structure. Diamond-like films are obtained in pure argon plasma. The addition of nitrogen leads to a dramatic increase in the graphite-like phase while the addition of hydrogen corresponds to the formation of carbon chains.

The initial stages of the chemical vapor deposition of carbon onto nickel substrates subjected to different mechanical abrasion treatments are studied by optical, scanning electron, and atomic force microscopies, as well as X-ray diffraction and profilometry. We find that the local accelerated deposition of carbon layers with a highly disordered structure, which occurs at the initial stages of the process, is the underlying cause of nonuniformity in carbon nanotube layers synthesized directly onto a metal surface. Enhanced deposition rates are observed at surface topography defects, including microcavities with a large surface-to-volume ratio. Open microvoids in the subsurface layer left behind by mechanical abrasion treatment also act as foci of the accelerated formation of carbon layers. The cause of this enhanced growth lies in the specific chemistry of the extended pyrolysis of hydrocarbons trapped in microvoids. A high carbon deposition rate results in the formation of carbon-containing materials with a highly disordered structure within such defects. Microscopic asperities and microprotrusions formed as a result of mechanical abrasion are sites of intensive hydrocarbon-induced dusting of the metal. Numerous microslits originate from these defects due to corrosion scattering, which in turn facilitate the emergence of sites for accelerated formation in limited volumes of carbon with a disordered structure.

The project of fourth-generation Ultimate Source for Synchrotron Radiation (USSR-4) is under development in Russia by leading of National Research Center “Kurchatov institute”. Some of diagnostic systems required for the new facility have to be developed or redeveloped to satisfy the features of the new facility. Hundreds beam position monitors (BPM) are installed along beam transfer lines, booster and storage rings to control the electron beam position. In booster and storage ring the electronics of BPM has to provide both the normally beam circulation and the first beam turn operation. It has to provide beam position monitoring in the bunch-by-bunch option for all operational modes [1]. In this manuscript we discuss the architecture of the BPM electronics, important aspects of the analog front-end, available components and a resulting performance of designed electronic module.

The local transverse photoconductivity of ultrathin (~4 nm) ZrO₂(Y) films with embedded single-layer arrays of Au nanoparticles (~2 nm in diameter) is studied by conductive atomic force microscopy. The ZrO₂(Y) films with Au nanoparticles are formed on glass substrates with transparent conductive indium-tin-oxide sublayers using layer-by-layer magnetron deposition followed by annealing. The peaks observed in the optical absorption spectra of the samples at the wavelength λ ≈ 660 nm are attributed to collective plasmon resonance in dense arrays of Au nanoparticles. The photocurrent between the microscope probe and the indium-tin-oxide sublayer is measured during photoexcitation of the contact between the probe and the sample surface through the transparent substrate by the radiation of a semiconductor laser diode at the plasmon-resonance wavelength. The increase in current through the probe of the atomic force microscope under photoexcitation is attributed to the photon-assisted emission of electrons from the Au nanoparticle into the conduction band of ZrO₂(Y) in a strong electric field applied between the probe and the indium-tin-oxide sublayer under plasmon resonance conditions.

The coadsorption of carbon-monoxide- and nitric-oxide molecules and their interactions on surfaces of Al−Mo(110) alloy and the system resulting from its oxidation (Al−Mo−O) are investigated using an array of spectroscopic techniques (X-ray photoelectron, Auger electron, infrared, and thermal-desorption spectroscopies), low-energy electron diffraction, and work-function measurements in ultra-high vacuum. Al−Mo(110) alloy is fabricated by the thermal annealing (at 800 K) of an aluminum film several layers thick deposited onto the Mo(110) surface. Aluminum atoms diffuse into the substrate to yield a surface alloy of hexagonal structure characteristic of stoichiometric Al₂Mo alloy. Unlike dissociative adsorption on both Mo(110) and Al(111) surfaces, CO and NO adsorb molecularly at the surface of Al−Mo(110) alloy. At 200 K, the adsorption of CO molecules on the Al−Mo(110) surface containing pre-adsorbed NO molecules has a dramatic effect on the latter by displacing them to higher-coordinated adsorption sites and at the same time causing their molecular axis to tilt toward the adsorbent surface plane. Heating this system to 320 K results in the reduction of nitric oxide by carbon monoxide to yield CO₂ and surface nitrides. This can be a consequence of surface reconstruction that leads to the formation of additional adsorption/reaction sites at the Al/Mo interface and to changes in the substrate’s d-band filling as a result of alloying. The oxidation of CO by NO proceeds with a markedly higher efficiency at the surface of the Al−Mo−O system; this system results from oxidation of the Al−Mo(110) alloy by oxygen at 700 K and exposure up to 1500 L.

To provide the necessary electrical conductivity of microchannel plates, it is proposed that a thin RuO_x film be used by means of its pulsed metalorganic chemical vapor deposition onto the walls of the channels. The chemical composition, structure, electrical conductivity, and secondary electron emission are studied using satellite samples. The RuO_x film is shown to have a globular structure with a characteristic size of ~100 nm. The core of each globule (average size, ~21 nm) represents a mixture of the Ru and RuO₂ phases with a ratio of nearly 4 : 6. The other part of the globule is amorphous with a Ru : RuO₂ ratio of ~5.4 : 4.6. The electrical conductivity of the films has a metallic character. The secondary-electron-emission coefficient of RuO_x increases from 2.5 to ~4 after annealing in air at temperatures up to 800°C.

A computer program is developed to study ion reflection from solid surfaces. The program uses the cutoff Coulomb potential, the binary collision approximation, and the model of local inelastic energy losses. For a fixed ion-target combination, the reflection coefficient is calculated as a function of the ion energy and incidence angle. A reflection theory for the scattering cross section which depends on the transferred energy in accordance with the power law is constructed. Good agreement of the simulation results with the experiment and the theory is obtained.

The kinetics of oxidation of 10–40-nm-thick titanium films in air is studied by combining X-ray and neutron reflectometry. It is found that the thickness of the oxide layer on the surface of Ti nanolayers does not increase after keeping the samples at room temperature for a year. At temperatures of 100–300°C the oxidation kinetic curves of Ti nanolayers are described by a logarithmic dependence. The obtained results indicate the applicability of the Cabrera–Mott and Evans model approximations to describe the oxidation process of Ti nanolayers in air. Examples of the application of Ti nanolayers in polarizing mirrors and a neutron mirror spin flipper are given.

Gradient coatings with a thickness up to 160 μm are obtained by the low pressure plasma spraying of NiCoCrAlY, ZrO₂–Y₂O₃(7%), and HfO₂–Y₂O₃(9%) powders and their mixtures. The coatings are studied by scanning electron microscopy and nuclear backscattering spectrometry of protons. According to the spectrometry data, the thickness of the gradient coatings (so-called “mass” thickness) is significantly less than the geometric thickness. It indicates a rather high porosity of the coatings (20–30%) and is explained by the presence of nanostructured areas in them. The difference between the geometric and mass layer thicknesses is less significant in the case of a thicker coating due to sintering of the particles during the spraying of subsequent upper layers. The mass thicknesses of the NiCoCrAlY + ZrO₂–Y₂O₃(7%) and ZrO₂–Y₂O₃(7%) + HfO₂–Y₂O₃(9%) layers are greater than the thicknesses of the main layers due to the formation of additional transition zones of mixed composition at the interfaces. The NiCoCrAlY + ZrO₂–Y₂O₃(7%) layer is thicker than the ZrO₂–Y₂O₃(7%) + HfO₂–Y₂O₃(9%) layer due to the higher porosity of the ceramic layer.

Microchannel plate surfaces are studied by means of a laboratory spectrometer for fluorescence analysis and a synchrotron radiation source. Methods of mathematical statistics make it possible to estimate the degree of homogeneity and compare the chemical composition of the surfaces of different microchannel-plate samples. The conditions are determined, under which a synchrotron radiation beam excites X-ray fluorescence that propagates in the hollow microchannels. The X-ray diffraction and spatial distribution of fluorescence at the exit of the microchannel plates for an energy corresponding to the region of anomalous dispersion near the SiL_2,3 absorption edges are studied experimentally and theoretically. In the long-wavelength X-ray radiation range, the relationship between the elemental composition of the microchannel-plate surfaces and the angular distribution of synchrotron radiation transmitted through microcapillaries is studied.

Fourth-generation synchrotron radiation sources demand new quality for the electron beam diagnostic systems. Some of diagnostic system elements have to be accurately developed or redeveloped due to match the new requirements. Beam position monitor (BPM) is a most used detector and tens (even hundreds) BPMs are installed in numerous positions along beam transfer lines, booster and storage rings. Modern approach to this device development assumes such features as short transient time, wide bandwidth, high sampling rate, low noise architecture and reasonable production and maintenance price. As a part of the system, the BPM electrodes should meet all those requirements. In this article we describe a development procedure for high quality capacitive electrodes for the BPM. 3D electromagnetic model allows estimation of the sensitivity, frequency response and tolerance requirements for the manufacturing of hundreds of monitors. Presented here equivalent scheme for the electrodes is a basis for the BPM electronics design.

The effects the spectrum of incident radiation can have on photobiological processes are studied experimentally and theoretically. The potential effective fluxes of visible light are calculated for energetic and regulatory processes. With these data at hand, we find a correlation between the spectral photoresponse and the energy characteristics of plant photoreceptor and photosynthesis systems. A qualitative model for a photosensitive organic system is formulated as a circuit diagram that includes semiconductor photocells. The thermodynamic and electrical parameters of the modeled system are described. We draw parallels between the functioning of phototransistors and photoreceptor complexes PHOT, CRY, Ph(660), and Ph(730). The control parameters of the energy-distribution process in a living system are estimated using mathematical modeling and an experimental model based on photocells.

Water-molecule channeling in bundles of carbon nanotubes in the presence of vacancies on walls and adsorbed atoms inside the tube is studied using the computer-simulation method. Estimation calculations show that channeling in the intertube space or dechanneling lead to the fast dissociation of water molecules. Therefore, studying the channeling process in bundles can be reduced to considering channeling in an individual carbon nanotube. It is shown that a change in the parameters of the beam of passed particles makes it possible to discover structural damage done to the bundles of nanotubes. A comparison with analogous results on a hydrogen atom and molecule channeling is made. It is discovered that the use of triatomic molecule channeling to study bundles of carbon nanotubes makes it possible to reveal structural imperfections, such as atoms adsorbed inside the tubes or vacancies on the walls, with a high effectiveness.

The isothermal dependences of the lattice properties of a nanocrystal on its the size and shape are investigated using the nanocrystal RP model which contains both lattice vacancies and delocalized (diffusing) atoms. A Gibbs surface model is proposed in which a part of the cells is vacant and a part of the atoms are in the delocalized state. The model takes into account that a part of the atoms on the Gibbs surface are delocalized in the bulk manner and the others, on the surface manner. The calculations are performed for argon atoms, which interact by means of the Mie‒Lennard‒Jones pairwise potential. The state equation (P) and the isothermal elastic modulus (B) for argon macro- and nanocrystals along the isotherm T = 10 K are calculated. The calculated data for the macrocrystal are shown to agree well with the experimental data. The isochoric and isobaric dependences of the Debye temperature Θ, the first (γ) and second (q) Grüneisen parameters, the specific surface energy σ, and the functions B and B'(P) = (∂B/∂P)_T on the nanocrystal size and shape are studied. It is shown that the Θ, q, σ, B, and B '(P) functions decrease with an isomorphic-isobaric decrease in the nanocrystal size, while the γ value increases. However, in the case of an isomorphic-isochoric decrease in the nanocrystal size, the modulus of elasticity of argon increases. Upon a deviation of the nanocrystal shape from the energy-optimal shape (for the RP(vac) model it is cube), the size dependences of these functions are enhanced.

The computer simulation program SRIM, unlike other well-known programs (MARLOWE, TRIM.SP, etc.), predicts non-zero values of the sputtering yield in the case of glancing ion bombardment of smooth amorphous targets. To understand the reason for this and other differences, simulation of the sputtering of a germanium target bombarded with 0.1–10-keV ions is carried out using the OKSANA program. It is shown that SRIM insufficiently correctly simulates the initial stage of the sputtering process.