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

The results of an experimental study of the generation of surface plasmon-polaritons in the terahertz range are presented. The end-fire coupling technique has been used for generation, when the beam is focused on the metal–dielectric interface. It has been found that at normal beam incidence the efficiency of plasmon-polaritons generation is maximum and the half-width of the dependence of the generation efficiency on the angle of radiation incidence in the sample plane is 6.0° ± 0.5°. It is shown that the generation efficiency has a maximum at a certain shift of the center of the incident beam relative to the metal–dielectric interface. The half-width of this maximum is 590 ± 50 μm, which is consistent with theory within the error limits.

The shape of nanopores formed by the etching tracks of swift heavy ions in olivine is studied. The developed atomistic model of etching olivine, which is irradiated with swift heavy ions, predicts the possibility of producing nanopores with a noncircular cross section in olivine: the pores are elongated along one of the crystal axes. The shape of the cross section of these pores can be controlled by adjusting the orientation of the crystal relative to the irradiation direction. To verify this prediction, an experiment on the controlled irradiation of olivine with swift heavy ions followed by etching of the samples is performed. The shape of the resulting pores is studied using atomic force microscopy. The results show a qualitative agreement between the experimental and simulation data.

The main physical processes occurring during the impact of compression plasma flows with the eutectic silumin surface were investigated. Numerical modeling of heat transfer processes from the shock-compressed layer formed at the surface of the processed sample by the plasma flow was carried out. It was revealed that the plasma impact leads to melting of the near-surface layer and subsequent crystallization, as a result of which a modified layer was formed. The thickness of melted layer was estimated analytically by solving the classical heat conductivity equation. The experimental depth of the melted layer was also determined using scanning electron microscopy by studying samples cross sections. It was found that the calculated values of the melted layer depth exceeded the experimental ones. This effect was explained by the surface erosion during plasma impact with the material. The main erosion mechanisms were discussed. It was found that hydrodynamic movement of the melt was the main mechanism of surface erosion under compression plasma impact on eutectic silumin. A model was proposed to estimate mass loss during plasma treatment. Good agreement between the experimental and calculated data was obtained.

The interest in van der Waals materials is associated with their unique physical and chemical properties and prospects for technological applications. In this work, the object of study is highly oriented pyrolytic graphite as a model of such materials. The results of measurements by angle-resolved X-ray photoelectron spectroscopy are presented. The experiments are performed at detection angles of 0°, 60°, 80°, and 85° from the normal to the sample surface, which makes it possible to localize the signal produced by the upper layer of highly oriented pyrolytic graphite as much as possible. A method for reconstructing the differential cross section of inelastic electron energy losses from experimental X-ray photoelectron spectra is presented. Using this method, the differential cross section of inelastic electron scattering in highly oriented pyrolytic graphite is reconstructed at each detection angle. The obtained cross sections are compared with the cross sections reconstructed for graphene with a varying number of layers. The determining influence of collective plasmon electron energy losses on the formation of the energy loss spectrum in heterogeneous van der Waals materials is indicated.

For the first time, the dependence of the probability of ionization of helium atoms on the velocity of a low-energy hydrogen ion beam is taken into account when the first ionization potential of target atoms exceeds the ionization potential of the charged particle beam atoms. Formulas describing the dependences of the helium stopping power on the beam energy of monoenergetic protons and deuterons are obtained. It is shown that their application makes it possible to calculate the helium stopping power adequately to the available experimental results.

The parameters of electromagnetic radiation that should be generated during guiding of accelerated electrons (extended sliding interaction of accelerated electrons with a dielectric surface) pressed to the surface of a dielectric plate by an external electric field are calculated. The model of the effect (guiding) is proposed based on an analysis of the solution to the Hamilton equation for the motion of electrons in an external electric field and in the electrostatic field created by electrons deposited on the surface of a dielectric plate. Superposition of these fields leads to the fact that during guiding, electrons experience transverse vibrations relative to the surface of the plate, i.e., acquire lateral acceleration. And this, as is known, should lead to the generation of electromagnetic radiation, the frequency and intensity of which depend on the electron energy, similar to the radiation of undulators and wigglers. Calculations show that when electrons are guided, radiation should be generated depending on their energy. The maximum of its intensity is in the region from the IR to the radio frequency range.

A crystallographic theory of martensitic transformations has been developed, which adequately describes their real mechanisms. A mathematical description of real processes occurring during martensitic transformation has been obtained as a product of four matrices: P₁ = R₁PB₁Г, where Г is the shear deformation of the austenite lattice, В₁ is additional “pure” deformation, the main axes of which coincide with the shear direction, with the normal to the shear plane and, accordingly, with the transverse direction, Р is the deformation of the lattice martensite with an invariant lattice, and R₁ is a slight rotation of the martensite plate to obtain an invariant plane (relaxation rotation). All four processes occur almost simultaneously, but in the specified sequence. Crystallographic analysis of eight alloys based on the theory allowed obtaining a number of important results. A relaxation rotation has been detected during martensitic transformations. A relationship has been found between the relaxation rotation and martensite texture scattering. The mechanism of packet structure formation during polymorphic transformation in a zirconium single crystal has been established. The real mechanisms of deformation during martensitic transformations in these alloys have been established.

This work presents a device for determining the contour of the visible area of optical elements (contourograph) designed for precise correlation of the coordinates of the visible area of the optical part with its physical dimensions. The developed device ensures the determination of the coordinates of the processed surface with an accuracy of ±2.5 μm, which is necessary for high-precision ion-beam processing. The contourograph is capable of outlining objects of arbitrary shape, including curved ones, as well as the contours of objects oriented at arbitrary angles relative to the linear motorized translators of the device. The high accuracy of determining the position of the processed surface directly affects the quality of ion-beam processing, which allows for significant improvement in the characteristics of the optical element and, consequently, the optical system as a whole. During the work, the contourograph was successfully applied in the manufacturing of a substrate for the element of a two-mirror monochromator for station 1-1 “Microfocus” of the 4th generation synchrotron “SKIF” (Novosibirsk, Russia), demonstrating its practical significance and efficiency. By using the contourograph, an optical surface with the required characteristics was achieved, with the root mean square deviation of the surface reduced by 25 times, from the initial 25.7 to 1.0 nm.

The effect of the volume capture of fast charged particles in a curved single crystal is studied. The transverse energy losses, the hovering effect, and the criterion for the volume capture of fast charged particles are studied. Possible mechanisms of volume capture are considered: transverse energy losses due to crystal excitation by a fast charged particle (proton, lepton), multiple scattering of particles in a curved crystal, and elastic scattering and diffraction of particles in a curved crystal. It is shown that in the hovering region, the ratio of the loss rates of the transverse and longitudinal energy of fast charged particles increases significantly compared to the ratio of the longitudinal and transverse energies and is equal in order of magnitude to the ratio of the off-diagonal elements of the inverse dielectric permittivity matrix to the diagonal ones. It is established that the effect of the volume capture of fast protons (leptons) is due to diffraction in a curved crystal, as well as the effects of damping of the off-diagonal elements of the particle density matrix. The proposed diffraction mechanism is based on taking into account the quantum coherent scattering of a fast proton (lepton) in a curved crystal.

The report presents the results of studying the process of periodic relief nucleation on the silicon surface irradiated with a 30 keV focused beam of gallium ions at ion beam incidence angles θ = 30°, 40°, and 50°. It is shown that the following factors initiate the origin of periodic relief: gallium precipitates in the near-surface silicon layer (θ = 30°), topographic inhomogeneity in the form of a hole at the boundary of the bottom, and the frontal wall of the sputtering crater (θ = 40° and 50°).