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

The paper presents the results of surface hardening of samples made of D2 die steel by complex alloying with preliminary application of a saturating mixture to the surface of the sample, followed by exposure to an electron beam. The morphology and structure of surface layers after electron beam treatment have been studied. Microhardness, elemental and phase compositions, as well as wear resistance in terms of mass loss depending on time were determined. Complex alloying of boron-containing components together with electron beam processing leads to the production of layers with improved physical and mechanical characteristics. The structure of the surface layer, its hardness, structural and phase composition are subject to change. It was found that the alloyed sample has wear resistance from 2.4 to 3.8 times higher than the sample in the original state.

We investigated the influence of impact ionization on the laser ablation of silicon using ultrashort pulses in the near and mid-infrared ranges. Using electron microscopy and numerical modeling of the ionization process based on dynamical rate equations, we demonstrated that the transition to the mid-IR range significantly changes the mechanisms of plasma generation. In the near-IR range, photoionization (both multiphoton and tunneling) predominates, while the contribution of avalanche ionization becomes dominant for pulse durations exceeding 500 fs. Consequently, the smallest size of microstructures on the silicon surface during laser ablation is achieved for picosecond pulses, where the electron concentration in the generated plasma is low and laser beam defocusing is negligible. In contrast, in the mid-IR range, impact ionization becomes the dominant mechanism for increasing the electron density of the plasma, enabling high spatial resolution during the ablation process at the shortest pulse durations, as impact ionization proves to be more effective. The results of this study contribute to a better understanding of the mechanisms of laser radiation interaction with material surfaces and can be applied to optimize laser processing techniques in various fields.

The work is devoted to the study of the possibility of manifestation of the effects of dynamic diffraction of coherent X-ray radiation of relativistic electrons in a periodic layered medium with three layers in a period. Coherent X-ray radiation is considered as a sum of parametric X-ray radiation and diffracted transition radiation. The dynamic theory of coherent X-ray relativistic electrons in the periodic layered medium with three layers in a period is developed. Within the framework of the two-wave approximation of the dynamic theory of diffraction, expressions in real form are obtained that describe the spectral-angular and angular density of radiation. The possibility of manifestation of the effects of dynamic diffraction of coherent X-ray radiation is investigated. The effect of asymmetry of the electron field reflection relative to the target surface on the spectral-angular densities of parametric X-ray and diffracted transition radiation is shown. The possibility of a bright manifestation of the effect of anomalous photoabsorption in parametric X-ray radiation in the considered three-layer structure is shown. This effect is analogous to the well-known Borrmann effect for X-rays in a single crystal.

The behavior of the nanohardness of titanium-based alloys at various torque values during high-pressure torsion is considered. In this case, the linear lattice deformation and the change in dislocation density are taken into account. It is shown that the change in nanohardness along the radius has an oscillating character with a maximum at the center of the sample, and the corresponding curve in the absence of sample slip is symmetrical. The radial distributions of the linear size of the unit cell and the dislocation density are studied. It is shown that the rate of dislocation accumulation has anomalies at certain points of the sample radius.

Transparent conducting three-layer oxide/silver/oxide structures, in which wide-bandgap semiconductor materials ITO and IGZO were used as oxide top and bottom layers, were obtained by the rf magnetron sputtering method. Comparative studies of the morphology, microstructure, optical transmittance, and surface resistance of the obtained three-layer structures were carried out. It was shown that the IGZO/Ag/IGZO structure is characterized by higher optical transmittance in the visible spectral range (T_av = 75.7%) and lower surface resistance (R_surf = 3.8 Ohm/sq) compared to the ITO/Ag/ITO structure (T_av = 71.6% and R_surf = 3.9 Ohm/sq, respectively). Subsequent testing the stability of the three-layer structures to various heating modes revealed that both structures exhibit tolerance to thermal annealing at T ≤ 250°C both under vacuum and in air. Annealing of the three-layer structures in air at higher temperatures showed that the IGZO/Ag/IGZO structure retains its integrity and functionality up to T = 350°C, whereas integrity of the ITO/Ag/ITO structure is large-scale compromised at this temperature.

The work continues the series of studies of the effect of the anomalous temperature dependence of the luminescence of dislocation structures formed by irradiating silicon with Si⁺ ions and subsequent additional implantation of B⁺ ions. It was found that thermal treatments of the samples lead to a strong shift in the high-temperature maximum intensity of the D1 line on the temperature dependence. It has been shown that the duration of heat treatments affects the intensity of this maximum, its position, and the shape of the luminescence temperature dependence curve. A possible mechanism for the observed temperature behavior of dislocation luminescence is discussed.

This work presents the results of studying the physical–mechanical and tribological characteristics of vacuum-arc coatings with a multicomponent composition (TiBSiNi + Cr)N, deposited under two variants of the assisting action of gas-discharge plasma ions: using a conventional plasma source with a heated cathode and through a relatively new generation scheme involving beam-plasma formation. A comparison of the results shows a clear advantage of the new synthesis method for the specified coating. For instance, the hardness of the (TiBSiNi + Cr)N coating synthesized using conventional assistance with a plasma source featuring a heated cathode is 29 GPa, whereas the coating synthesized using the beam-plasma generation pattern has a hardness of 39 GPa. Simultaneously, a reduced surface roughness is observed for the coating produced using the beam-plasma generation system, compared to the coating synthesized with conventional assistance. This is evident both in the average deviation of the surface profile R_a and in the parameter for the height of surface irregularities R_z. This difference is likely related to a greater uniformity and integral density of the gas-discharge plasma in the beam-plasma generation mode, and consequently, to the higher effectiveness of its impact on the deposited coating. A significant difference in the tribological properties of the coatings produced by the two assistance methods is also identified. The average values of the friction coefficient and the wear parameter for the coating synthesized using conventional assistance (0.504 and 1.42 × 10^–7 mm³ N^–1 m^–1, respectively) are higher than those for the coating synthesized through the beam-plasma generation scheme (0.434 and 0.99 × 10^–7 mm³ N^–1 m^–1). Moreover, in situ X-ray diffraction analysis reveals that during heating in air, the phase composition of the (TiBSiNi + Cr)N coating produced using the beam-plasma generation scheme remains stable up to a temperature of 1075°C.

The effect of isochronous annealing in vacuum at temperatures of 100–400°C on the forward and reverse current-voltage characteristics of Cr–SiC(4H) Schottky diodes is studied. Diodes of different sizes are manufactured using the same technology based on one lightly doped (~4 × 10¹⁴ cm^–3) epitaxial layer. The current-voltage characteristics are close to ideal in all cases, but their significant spread before annealing, a decrease in the spread, and a shift to the low-voltage region as a result of annealing at 400°C were found. It is assumed that the main diode is in all cases is shunted by a parasitic diode, the barrier height of which is reduced as a result of annealing.

Ion beam technology is an excellent tool for changing and investigating the structural and surface properties of crystals. In this paper, the possibility of modifying the surface of a thin LiF film under irradiation with low-energy Cs ions with an energy of 1 keV using the SRIM software method is investigated. The results of the study show that the average range of cesium ions is 51 Å, and the average surface binding energy is 2.8 eV. Due to the transfer and distribution of the energy of bombarding ions to the atomic lattice and as a result of the displacement of the lattice atoms from their initial positions, it is possible to obtain the value of displacement defects. The defect formation profile was investigated depending on DPA, which implies that the maximum peaks of defect displacement for LiF are at a crystal depth of 16 Å from the surface.

A theoretical calculation was conducted to determine the potential for and the conditions under which mineral phases may form. It has been established that under these conditions the formation of a mixture of calcium phosphates is possible, with hydroxyapatite being the most stable phase. Based on the calculated data, a synthesis was carried out, as a result of which it was established that the resulting sediments were represented by the phases of hydroxyapatite, octacalcium phosphate and brushite. It was found that the synthesized mixture of calcium phosphates can be used to create dense ceramics. Thus, the range of use of synthesized materials is expanding. It has been proven that in an SBF solution a calcium phosphate layer is formed on the surface of the samples, which indicates the bioactivity of the samples. The prospect for further development of the topic is the use of ceramics as materials for replacing bone defects or a biologically active layer on the surface of implants.