编号 5 (2024)

Structure of adsorption layer of long-chain monoatomic alcohols: 1-dodecanol and 1-tetracosanol at the interfaces n-hexane – water and n-hexadecane – water in the vicinity of “liquid – vapor” thermotropic phase transition is investigated by the method of X-ray reflectometry at synchrotron source. Model-independent structural data obtained on the adsorption layers under investigation deviate considerably from the structural parameters which have been proposed previously within a model-based representation and discussed in previous publications on said systems. It is shown that in the low-temperature mesophase the adsorption film consists of a Gibbs monolayer, a transitional liquid region with thickness of two to three monolayers ~50 Å and an extended (wide up to 200 Å) layer of micelles. Presence of a plane of the closest approach of micellar layer to the adsorption film at the interface is established. Transition to the high-temperature mesophase is followed by liquefying and partial evaporation of alcanol film along with observed depletion of micellar layer down to its complete disappearance.

Composite mechanoluminescent materials (composites) based on epoxy resin transparent in the visible range of spectrum and fine-dispersed powders of mechanoluminescent phosphors SrAl₂O₄:Eu²⁺, Dy³⁺ and Sr₄Al₁₄O₂₅:Eu²⁺, Dy³⁺ were obtained. The mechanoluminescence and photoluminescence spectra of composites under the combined influence of short-wave (λ = 405 nm) and long-wave (λ = 1.06 µm) laser radiation were studied. The attenuation of optically stimulated antistokes luminescence of the composite under the influence of a sequence of pulses of longwave laser radiation was investigated. The composite was pre-irradiated with shortwave laser radiation. The obtained composite was used to visualize heat propagation and thermal deformations in metal plates arising under the action of powerful laser pulses and distribution of deformations under mechanical impact. For this purpose, a thin layer of the composite was applied to the surface of the materials under study. The composite had good adhesion to the surface of the materials and a high yield of mechanoluminescence, which allowed to visualize the distribution of temperature and surface deformations with a good spatial and temporal resolution.

The article proposes a method of temperature activation–relaxation of the permittivity for determining the activation energy of defects in ferroelectrics using lead zirconate–titanate Pb(Zr,Ti)O₃ samples as an example. This method is based on the analysis of relaxation of the permittivity after thermal annealing and the analysis of the temperature activation of the permittivity of the Pb(Zr,Ti)O₃ ferroelectric. The equality of the activation energy corresponding to the process of migration of oxygen vacancies and the thermal energy of the decay of the domain structure was established, which was confirmed by studying the surface of the samples by scanning electron microscopy. When this temperature was reached, the surface of the domain walls was detached from oxygen vacancies, which are pinning centers. This manifested itself in photographs of the microstructure as a change in the ordering of the domains emerging on the surface of the sample, which led to an irreversible decrease in the permittivity of the sample. For the obtained activation energies, the physical process of domain wall motion activation is established, which is determined by their pinning on structural defects (oxygen vacancies). It is assumed that the irreversible decay of the domain structure occurs when the domain walls are displaced by distances exceeding the elementary lattice parameter of the ferroelectric. The proposed method can be part of a comprehensive study that includes electrophysical, microscopic and X-ray methods.

Hard wear-resistant carbon coatings were deposited from accelerated C₆₀ ions at temperatures of 200 and 300°C. It has been established that the mechanical properties of the coatings are determined by the substrate temperature (T_s) and the energy composition of the beam. The hardness of coatings deposited from C⁺₆₀ ions with an energy of 7 keV exceeds 50 GPa and is virtually independent of T_s. The presence of C₆₀²⁺ and C₆₀³⁺ with an energy of ~14 and 21 keV, respectively, in the beam leads to a result that is not typical for carbon coatings – the hardness increases by more than 1.3 times with an increase in T_s from 200 to 300°C (from 31.6 GPa to 41.6 GPa). In this case, according to Raman spectroscopy data, the size of graphite nanocrystals in the coating increases with temperature up to almost 2 nm. Coatings obtained under conditions of irradiation with C₆₀²⁺ and C₆₀³⁺ ions are characterized by minimal wear (1.5×10^–8 mm³/N∙m, T_s = 200°C) and minimal friction coefficient (µ = 0.05 for T_s = 300°C). We attribute the unusual dependence of hardness on T_s and the improvement in the tribological properties of coatings to the formation of a composite structure based on a diamond-like matrix and graphite nanocrystals in this range of T_s.

A technology was developed for activating ion-implanted dopants in silicon-on-insulator layers at a low annealing temperature (600°C) using the pre-amorphization technique of a silicon device layer. In the case of phosphorus implantation, silicon was amorphized directly by dopant ions. In the case of boron implantation for pre-amorphization, the layers were preliminary irradiated with argon or fluorine ions. Complex diagnostics of the implanted layers was carried out using secondary ion mass spectrometry, X-ray diffractometry and small-angle X-ray reflectometry. The combination of methods made it possible to characterize the impurity distribution, the degree of silicon crystallinity, the layer thicknesses, and the interface widths in structures. The results of diagnostics of the structure and composition correlate well with calculations in the SRIM software package and the electrophysical characteristics of the layers after annealing. It was shown that the use of argon for pre-amorphization of silicon interfered with the recrystallization process and did not make it possible to achieve acceptable electrical characteristics of the doped layer. Amorphization with phosphorus and pre-amorphization with fluorine during boron implantation allowed obtaining the required values of the resistance of the doped layers after annealing at a temperature of 600°C. The use of a complex approach made it possible to optimize the modes of amorphization, ion doping, and annealing of silicon-on-insulator structures at low temperatures, necessary for the creation of light-emitting device structures based on silicon-germanium nanoislands.

Using the methods of secondary ion mass spectrometry, elastic peak electron spectroscopy and Auger electron spectroscopy, the elemental and chemical composition of the surface, concentration profiles of the distribution of atoms over the depth of silicon implanted with O₂⁺ ions with energy E₀ = 1 keV at a dose of D = 6 × 10¹⁶ cm^–2 were studied. It was found that oxides and suboxides of Si (SiO₂, Si₂O and SiO_0.5) were formed in the ion-doped layer, and it also contained unbound O and Si atoms. Post-implantation annealing at 850–900 K led to the formation of a stoichiometric SiO₂ layer ~25–30 Å thick.

The transition radiation of a charged particle in the simplest case of its incidence onto an infinite, perfectly conducting plane can be described using the method of images known from electrostatics. The same method makes it possible to find the field distribution in more complex cases, such as the field created by a point particle in the presence of two intercepting conducting planes, the angle between which divides exactly the angle of 180°. Based on the method of images, a description is given of the transition radiation that occurs when a fast-charged particle falls on a target in the form of two conducting half-planes intersecting at the right angle (on the inside of the dihedral angle). The features of the radiation emitted by fast and slow particles are qualitatively considered, and their visual interpretation is given. The possibility of using interference effects arising from radiation to monitor beams of charged particles is discussed.

The contributions of grain boundary and dislocation mechanisms to the experimentally established strengthening of pure Al samples obtained by consolidation of thin foils by high pressure torsion technique were estimated within the framework of well-known theoretical models using structural parameters (sizes of coherently scattering domains and lattice microstrains) determined by X-ray diffraction. Good agreement between the calculated values and the hardness of deformed and aged samples was found, and possible reasons for their differences for the initial foils were discussed. The influence of deformation and aging on the relative contributions of the analyzed mechanisms to the strengthening of samples consolidated from both Al foils and the rapidly quenched Al_95.8Mn_3.8Fe_0.4 ribbons was determined. The structural features of samples processed by high pressure torsion and the relationship between structural parameters and mechanical properties were discussed.