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

Assigning a quantum of angular momentum (hbar ) to a two-particle system results in a halving of the calculated value of the magnetic flux quantum. The measured value of the magnetic flux quantum turned out to be half the size of F. London’s quantum. Since then, it has been believed that the magnetic flux quantum is created exclusively by Cooper pairs and that it is half the size of F. London’s quantum. The aim of the study is to rethink these circumstances. The geometric shape of the electron is unknown. However, it is believed that it is neither a ball nor a sphere. This follows from the formula for its classical radius. The complete uncertainty of the electron shape allows its spin to be consistently represented as the angular momentum generated by a material point with the mass of an electron rotating in a circle of an indefinite radius (arbitrarily small, and its value is irrelevant). This approach may have drawbacks, but it also has a significant advantage in the form of the ability to use a ready-made formula for the magnetic flux created by the “current” of a single electron. In reality, there is a quantum of F. London, a quantum of magnetic flux caused by the electron spin, and their superposition (quasi-quantum). It (quasi-quantum) was measured in 1961.

Currently, thin nanoporous Ge layers are applied in various technological devices, for example, in anode designs of lithium-ion batteries, IR-absorbing gas sensors, etc. A separate interesting application of such layers is their use as highly effective antireflection optical coatings for various photodetectors and solar cells. This study is devoted to the problem of creating an antireflection coating on a c-Ge surface using low-energy high-dose implantation of ¹¹⁵In⁺ ions in a vacuum, as opposed to the generally accepted chemical method, which leads to the accumulation of chemical reaction residues in the created nanoporous structures. The study results of the surface modification of polished monocrystal c-Ge substrate irradiated with ¹¹⁵In⁺ ions with an energy of 30 keV at a current density of 5 μA/cm² and a wide range of high doses of 1.0 × 10¹⁴–7.2 × 10¹⁶ ion/cm² are presented. Morphological analysis of surface topography was carried out using high-resolution scanning electron microscopy. The appearance and change in the morphology of porous layers with increasing ion dose were determined. At the lowest dose value of 1.8 × 10¹⁵ ion/cm², a porous structure in the form of a honeycomb with nm-sized round holes is formed. When the critical dose value of 1.9 × 10¹⁶ ion/cm² is exceeded, a spongy porous structure is formed by intertwining nanowires, geometric parameters of which do not further change with increasing dose. By measuring the optical reflection spectra of the implanted layers, it was shown that the formed material is characterized by a low reflectance in the spectral region of 220–1050 nm and can serve as an effective antireflection coating.

The size of quantum dots significantly influences the chemisorption process at graphene surface, affecting adsorption strength, interaction dynamics and overall performance in various applications. This relationships is primarily driven by quantum confinement effects and surface area variation. Chemisorption of quantum dots onto graphene introduces new pathways for charge transfer, where electron flow can occur due to differences in the Fermi level of graphene and the energy states in the QDs. Based on Newns—Anderson model, the chemical adsorption of spherical quantum dot at graphene depending on its size and normal distance between them were examined. Through a self-consistent computational scheme, the determination of occupation numbers, energy-level positions solved numerically.

A new method for recording fine structures of X-ray diffraction patterns formed in 3-block interferometers with a violated ideal geometry is presented in this work. To apply and verify the proposed method a new monolithic 4-block diffraction system is designed, manufactured, and tested. It consists of 3 thin blocks forming a 3-block interferometer with a violated geometry, and additional 4th thick block in the reflection mode. The inclusion of the 4th thick block enables the observation of fine structures of interference patterns formed in a 3-block defocused interferometer. It was shown that an interference pattern is formed in a 3-block interferometer in the form of families of parallel stripes (lines) in a plane perpendicular to the diffraction vector when its ideal geometry is violated. It was confirmed that the thick block increases the pattern size in the scattering plane, but does not add new information to the interference pattern. However, the fine structure of X-ray interference patterns obtained from 3-block interferometers with violated geometry can also be revealed when their splitter and mirror blocks are thin, while the 3rd block analyzer is thick. The limits for reducing the period of interference stripes until their complete disappearance due to the defocusing, as well as “allowed violations” of the ideal geometry of real 3-block interferometers (when the interference still is observable) are determined. Analysis of X-ray diffraction patterns formed in both a 3-block defocus interferometer and a narrow-gap double-crystal system has revealed their similarity.

The evolution of the phase composition of a metal-ceramic material formed by direct laser deposition using synchrotron radiation has been studied. Electron microscopy and X-ray phase analysis demonstrate that active formation of secondary phases of compounds occurs during repeated remelting in the process of multilayer deposition. Insignificant formation of secondary phases occurs during single-track deposition due to the short lifetime of the molten pool. It is established that an increase in the concentration of secondary phases leads to an increase in the material microhardness.

In this work, oriented arrays of InAs nanowires (NWs) and InAs/InP core-shell nanoheterostructures based on NWs synthesized by molecular beam epitaxy were studied. A high surface density of NWs in the array was demonstrated (5–10 NW/μm²). High-resolution transmission electron microscopy data showed that with shell thicknesses up to 15–20 nm, pseudomorphic growth of InP is possible on the side faces of InAs NWs and with shell thicknesses greater than 20 nm, complete relaxation of elastic stresses occurs. It was found that in radial heterostructured NWs with a thin InP shell, defects are formed only in the apex region, while no defect formation is observed at the radial heterointerface.

When excited by beams of runaway electrons with a duration of 100 ps, the pulsed cathodoluminescence of alkali halide crystals, cerium-doped yttrium-aluminum garnet ceramics, and synthetic gems (ruby, sapphire and diamond) was studied. The runaway electron beams were generated in the cathode-anode gap filled with atmospheric pressure air and focused by a non-uniform magnetic field with an amplitude of B ≈ 0.6 T into an area with a diameter of 15 mm. A comparative analysis was carried out between the findings and pulsed cathodoluminescence parameters of the same samples excited by an electron beam with a duration of 2 ns and a current density of 130 A/cm² generated in a vacuum diode. In the case of irradiation with the runaway electron beams, the formation of F-centers has not been observed in alkali halide crystals, that arises out of a reduced radiation impact on samples. Thus, the spectral information is not distorted. When excited by a picosecond runaway electron beam, the decay kinetics of the Ce³⁺ luminescence band in yttrium-aluminum garnet ceramics is described by an exponential function with a characteristic time of 100 ns. When the ceramics are irradiated with a nanosecond electron beam with a higher fluence, the kinetic curve has a more complex shape with an additional maximum in the microsecond range due to the appearance of an extra pumping mechanism for the cerium emissive level. The luminescence spectra and kinetic parameters of the synthetic gems are identical in both cases. The difference is manifested only in the emission intensity, which is much weaker when samples are exposed to irradiation with picosecond runaway electron beams.

Hydrogen sorption and desorption in Zr and Nb monolayer coatings and in nanolaminated Nb/Zr systems with individual layers of different thicknesses were studied. The coatings obtained by magnetron sputtering were subjected to hydrogenation at 350°C and 10 atm. Hydrogen absorption was analyzed using kinetic curves, while desorption was studied using thermal desorption spectroscopy. It was found that the maximum hydrogen content was achieved in the system with individual layers 50 nm thick. This is due to the optimal ratio of Nb/Zr interphase boundaries and the volume of the zirconium layer, which contributes to efficient hydrogen accumulation. With a decrease in the layer thickness to 25 and 10 nm, an increase in the number of interphase boundaries does not lead to an increase in sorption capacity due to the limited volume of zirconium. In samples 100 nm thick, the sorption capacity decreases, which is due to a decrease in the proportion of interfaces and slowdown in hydrogen. diffusion. Analysis of thermal desorption curves showed that the hydrogen release temperature depends on the layer thickness. In the thermal desorption spectra, the peak shifts to the low-temperature region with increasing heating rate, which is associated with dynamic changes in hydrogen trap states and a decrease in internal stresses. This leads to upward hydrogen diffusion. The obtained results demonstrate the possibility of targeted control of hydrogen sorption and desorption by optimizing the architecture of multilayer systems. This opens up prospects for the development of functional coatings and thin-film hydrogen storage materials with adjustable characteristics.

The study introduces a concept for an undulator beamline at a synchrotron radiation facility designed to combine confocal X-ray fluorescence microscopy (сonfocal μXRF) with micro-X-ray absorption near edge structure spectroscopy (μXANES). The optical layout employs a compact diamond channel-cut monochromator positioned near the focus of the undulator beam. The analysis includes an evaluation of the thermal load on the diamond monochromator and a simulation of the steady-state temperature distribution and thermally induced deformations in the crystal under water-cooling conditions. In maximum thermal load regime, the slope error of the deformed surface of the crystal’s first lamella remains significantly smaller than the angular convergence of the undulator beam, its angular size at the sample, and the rocking curve width of the crystal. The study also estimates the energy resolution of the diamond monochromator C(111), considering both the beam convergence and the temperature difference between the crystal lamellae. The results demonstrate that a diamond monochromator can operate near the focus of a high-power undulator beam at a fourth-generation synchrotron source, confirming the feasibility of the proposed beamline design.

The dynamic mechanical analysis using low-amplitude harmonic oscillations in addition to the main quasi-static load was employed to determine the storage modulus E ', the loss modulus E ", and the mechanical loss factor tanδ. A comparative description of the static and dynamic viscoelastic properties of softwood (pine, spruce, and larch) and hardwood (oak, linden, and birch) species common in the Russian Federation was presented as a function of the frequency of the probing oscillations and the stress of the quasi-static load. The contribution of different frequencies to the overall viscoelastic response of softwood and hardwood was determined, and the effect of the additional oscillating load on the dynamic parameters of wood was estimated.