Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques最新文献

Composite mechanoluminescent materials (composites) based on epoxy resin transparent in the visible range of the spectrum and fine-dispersed powders of mechanoluminescent phosphors SrAl₂O₄:Eu²⁺, Dy³⁺ and Sr₄Al₁₄O₂₅:Eu²⁺, Dy³⁺ are obtained. The mechanoluminescence and photoluminescence spectra of the composites under the combined influence of short-wavelength (λ = 405 nm) and long-wavelength (λ = 1.06 µm) laser radiation are studied. The attenuation of optically stimulated anti-Stokes luminescence of the composite under the influence of a sequence of pulses of long-wavelength laser radiation is investigated. The composite is preliminarily irradiated with short-wavelength laser radiation. The obtained composite is used to visualize heat propagation and thermal deformations in metal plates arising under the action of high-power laser pulses and the distribution of deformations under mechanical impact. For this purpose, a thin layer of the composite is 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 allows us to visualize the distribution of temperature and surface deformations with a good spatial and temporal resolution.

The migration of hydrogen in a homogeneously hydrogen-saturated commercial titanium VT1-0 has been studied using a high-frequency electromagnetic field and an accelerated electron beam. The use of a high-frequency 50–1000 kHz electromagnetic field, which generates eddy currents in the material, made it possible to observe the process of hydrogen migration near the surface and in the depth of the sample. To accelerate the migration of hydrogen in the volume of the sample electron irradiation with an energy of 30–45 keV was used. The migration process was studied in an inhomogeneously hydrogen-saturated commercial titanium sample with a titanium nitride film deposited on its surface by magnetron sputtering. VT1-0 flat samples were saturated with hydrogen using the Sieverts method. The diffusion coefficient of hydrogen in titanium was determined from the change in the magnitude of the signal from the eddy current sensor along the depth of the sample and along the sample, as hydrogen migrated in the sample. The values of the diffusion coefficients of hydrogen along the surface and in the depth of the sample under equilibrium conditions and under stimulation by an accelerated electron beam were obtained.

The effect of ion velocity in the synthesis of nanopores with a noncircular cross section by the etching tracks of swift heavy ions in olivine is studied. The developed atomistic model of the etching of olivine irradiated with swift heavy ions predicts the possibility of synthesizing nanopores with a noncircular cross section in it. The model consists of connected blocks that describe the sequential stages of track formation and etching. The TREKIS Monte Carlo model describes the initial electronic and lattice excitations in the nanoscale vicinity of the trajectory of an incident ion. These results are used as initial conditions for the molecular-dynamics simulation of structural changes along the ion trajectory. The obtained atomic coordinates after cooling of the structurally damaged region serve as the initial data for an original atomistic model of track etching in olivine. The results of application of the model demonstrate that it is possible to control the cross section of resulting nanopores by changing the orientation of the crystal relative to the direction of irradiation. The presented simulation results for Xe ions demonstrate that the size of the resulting pores depends on the velocity of the incident ion, and not only on its linear energy losses.

The first results of the deposition of coatings from accelerated ions of fluorinated fullerene C₆₀(CF₃)₁₂ are presented. The coatings are formed at room temperature on Si substrates from a beam of singly charged ({{{text{C}}}_{{60}}}({text{C}}{{{text{F}}}_{3}})_{{12}}^{ + }) ions with an energy of 5 keV, as well as from an ion beam that also contains doubly charged ({{{text{C}}}_{{60}}}({text{C}}{{{text{F}}}_{3}})_{{12}}^{{2 + }}) ions and a certain amount of ionized fragments of molecules. The properties and structure of coatings obtained from accelerated ions of fluorinated fullerene are compared with the properties and structure of coatings obtained from accelerated fullerene C₆₀ ions under the same conditions. According to X-ray photoelectron spectroscopy (XPS), fluorinated fullerene coatings contain about 4% fluorine. Investigations of the coatings structure and chemical bonds by X-ray photoelectron spectroscopy and Raman scattering show that the presence of fluorine leads to a decrease in the content of sp³-bonds in the coatings and the formation of graphite-like sp²-structures. Coating hardness (H) and Young’s modulus (E) compared to C₆₀ ion coatings decrease from 36 to 18 GPa and from 245 to 133 GPa, respectively, while the H/E ratio remains the same (~0.14). Tribological tests have shown for all coatings the friction coefficient is close to 0.1. All coatings are also characterized by a very low wear, less than 10^–7 mm³/(N m). For coatings obtained from C₆₀(CF₃)₁₂ ions, the contact angle is ~76°–78°. In the absence of fluorine, for the coating obtained from C₆₀ ions, it is ~90°.

Ptychography today is considered the most natural and effective method for approaching the diffraction limit of optical resolution. The principal scheme of a ptychoscope does not contain refractive or focusing elements and includes a coherent light source, a platform for moving (macroscopic) object, and a detector for registering radiation passed through or reflected by the object associated with a computer for processing diffraction patterns. In classical optics, the main task in achieving high spatial resolution is the correction and elimination of aberrations of optical systems, while in ptychography spatial resolution mainly depends on the reliability of registration and computer processing of diffraction patterns with large numerical apertures. The key idea of ptychography is to obtain an image by computer processing of overlapping diffraction patterns (scans). When moving the object it is assumed that the illuminating beam and the position of the detector remain unchanged. Ptychography is used in a wide range of radiation wavelengths from infrared to X-ray, and it is possible to do without imaging optics. In this work, the possibility of obtaining an amplitude-phase image of the surface relief of an object inclined to the incident one was studied.

Structure of the adsorption layer of unsaturated monoatomic alcohols, 1-dodecanol and 1‑tetracosanol, at n-hexane/water and n-hexadecane/water interfaces, respectively, in the vicinity of liquid–vapor thermotropic phase transition is investigated by the method of X-ray reflectometry with a synchrotron source. Model-independent structural data obtained on the adsorption layers under investigation deviate considerably from the structural parameters that have been previously proposed within a model-based approach and discussed for the said systems. It is shown that in the low-temperature mesophase the adsorption film consists of a Gibbs monolayer, a liquid transition 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 the micellar layer to the adsorption film at the interface is established. Transition to the high-temperature mesophase is accompanied by liquefying and partial evaporation of the alkanol film along with depletion of the micellar layer down to its complete disappearance.

In this paper, we propose a model to describe the distribution of electrons near the track of a fast ion. The dependence of the fast-electron flux on time, layer depth, and radial variable is modeled taking into account the statistical weight of each trajectory. The pulse duration in the electron-flux distribution was found to be fractions of ps while the radial size of the cylindrical region, where the transport of fast electrons occurs, reaches tens of angstroms.

The processes of generating phonons and electronic excitations by an oriented quantum particle in a crystal are considered. The probabilities of the excitation of phonons and plasmons are calculated. A theory of crystal excitation by a channeled particle with simultaneous photon emission is developed. The probability of a process with the fast particle transitioning into a virtual state after emitting a plasmon, followed by photon emission, is determined. The probability of the process involving photon and plasmon emission is of the same order of magnitude as the probability of the standard process with photon emission alone. The possibility of experimentally detecting the effect is assessed. It is demonstrated that all features of electronic and phonon excitations manifest as components of the radiation spectrum from a fast oriented charged particle in a crystal.

Molecular dynamic simulation was used to study the processes of molecular 2 to 14 keV C60 ion impact on the (100) Si surface at 0 to 1000 K. Tersoff-ZBL and Airebo interaction potentials were used, and electronic energy loss were taken into account as quasifriction force for fast particles. It is shown that, when single impact events are simulated, the target temperature does not affect the development of the displacement cascade but affects its thermalization and the formation of the crater on the surface. As the energy increases, the carbon penetration depth, the size of the formed crater, and the size of the rim increase. The sputtering coefficient of silicon atoms in this case increases linearly with energy, while for carbon atoms it reaches a steady-state value at 10 keV. A higher number of atomized carbon atoms in single impact events is found using the Tersoff potential compared to the Airebo potential. In the event of cumulative events, the formation of an etch pit is observed at the initial stage followed by carbon film growth. In the case of cumulative ion accumulation, the use of the Airebo potential yields a higher sputtering coefficient than the use of the Tersoff potential. The formation of carbide bonds in the crystal and the increase in their concentration with ion fluence slightly reduce the number of sputtered particles. Therefore, for the correct comparison of simulation results with experiment it is not enough to use the results of single impact event analysis. It is necessary to perform cumulative fluence accumulation simulation.

The results of comparative studies of the phase composition, diffuse reflectance spectra, radiation-induced absorption spectra, and the integral absorption coefficient of solar radiation upon irradiation of micro- and nanopowders of gadolinium oxide are presented. To assess the radiation stability of optical properties, the samples were placed in a chamber of an installation simulating space conditions, where diffuse reflection spectra were recorded in the range of 0.2–2.5 μm in a vacuum of 2 × 10^–6 Torr before and after each period of electron irradiation (E = 30 keV, Φ = (1–3) × 10¹⁶ cm^–2). Micropowders of rare earth elements are used to increase the radiation stability of materials by absorbing free electrons formed in them during irradiation during their transitions from the d- to f-shell. Nanopowders of rare earth elements added to micropowders of various compounds provide an additional mechanism for increasing radiation stability due to the annihilation of primary defects formed during irradiation on nanoparticles. The result obtained in this work is opposite to these mechanisms—the radiation stability of a micropowder is significantly (more than 4 times) higher compared to a nanopowder due to more intense absorption in the ultraviolet region for the nanopowder caused by their own defects. The paper gives an explanation of the results obtained.