Technical Physics最新文献

In this paper we investigate the adequacy of deep learning force field models for modeling amorphous bodies. A polymer with the studied physical properties, polyphenylene sulfide, was chosen as a test substance. The simulation results shows that the forces predicted by neural networks acting on polymer atoms are significantly different from the forces calculated by ab initio molecular dynamics methods. A qualitative comparison with the force field model of a simpler compound, black phosphorene, shows that feedforward neural networks are unsuitable for modeling complex amorphous substances.

In this paper, we present the results of processing metallic gallium in an ammonia vapor medium at 2 bar pressure by femtosecond laser pulses. The influence of the ammonia concentration and the mode of laser beam scanning on the result of laser action is considered. It has been established that an increase in the concentration of ammonia vapor and a change in the scanning regime lead to a radical change in the laser ablation process. A decrease in the scanning speed leads to the cessation of the ablation process and the development of the nitridation process of the gallium surface, accompanied by the formation of columnar structures up to 12 mm long and about 100 μm in diameter. The synthesized nanoparticles and structures were studied using scanning electron microscopy, Raman spectroscopy, and X-ray analysis.

The key elements of neuromorphic computing systems (NCS) are memristors—resistors with a memory effect—that can be used for simultaneous processing and storage of information. It is promising to create them in crossbar geometry, where memristors are located at the intersections of the transverse electrode buses. In this work, the influence of the area and geometry of contacts on the main memristive characteristics of parylene-based structures is investigated. The results obtained indicate the independence of such memristive characteristics as the switching voltage into the low-resistance (U_set) and high-resistance states (U_reset), as well as the resistance of the samples in the low-resistance (R_on) state, from the contact area. At the same time, resistances in the high-resistance (R_off) state increase with decreasing area, which confirms the single-filament model of resistive switching, and also makes it possible to increase the window of resistance in such structures.

The paper proposes an X-ray optical scheme of a lithograph with a transmissive dynamic mask and a synchrotron radiation source. The image of a dynamic mask in the form of holes of small diameter is transferred with a decrease to a plate with a resist using a Schwarzschild projection lens. The formation of a topological pattern will occur due to the coordinated operation of the system for scanning a plate with a resist and a microelectromechanical system of a transmissive type. Objectives with a reduction of 10 and 20 times for obtaining 10–20 nm images of 200 nm holes of the dynamic mask are considered. The scheme of illumination of the mask is calculated, which provides uniform illumination on a field of 10 × 10 mm². For the synchrotron Siberia-2 of the KISI on a bending magnet, the expected productivity of the lithograph will be up to 1/14 of a plate with a diameter of 100 mm per hour.

The results of studies of a solid-state closing switch for a high-current pulse switching are presented. The experiments were carried out on a laboratory facility with a capacitive energy storage run down a discharge circuit with electrical-explosive opening switch (EEOS) by a current pulse with an amplitude ~450 kA. The discharge circuit consists of two sections separated by a branch with a solid-state closing switch. A metal foil of the EEOS can be located in an interelectrode gap of the closing switch. The operation of the EEOS leads to a breakdown of the insulation of the closing switch, as a result of which an effective shunting of the section of the discharge circuit containing the EEOS occurs. The developed combined solid-state closing switch in the future is capable of providing multi-channel switching of a high-current pulse to the load synchronously with the EEOS operation.

Silicon nitride membranes were experimentally obtained as substrates for biological samples, which are examined using a microscope with an operating wavelength of 13.8 nm. The free-hanging films obtained have a size of up to 1.5 × 1.5 mm², which makes it possible to select an area of interest for investigation on the sample on the order of tens to hundreds of microns. The mechanical strength of the membranes satisfies that the samples do not tear the membranes and withstand transportation. The results obtained are an import-substituting technology for the manufacture of Si₃N₄ membranes. The resulting membranes have a transparency of more than 40% in the range of the “water transparency window” (2.3–4.4 nm) and EUV (13–15 nm). The developed technology will become the basis for creating cuvettes for living biological samples for soft X-ray microscopy studies.

The planishing of the surface of solids is aimed to minimize its roughness, downgrade a content of larger cracks in the modified layer, and, in general, reduce a thickness of the latter one. However, the abrasive processing induces residual stresses in the surface layer. The stresses relax through the motion of dislocations but in superhard materials like corundum or silicon dioxide, is extremely limited. In the present work, the role of the modified surface layer in corundum was studied within the context of the method and regime choice which affect the surface processing the mechanical characteristics of corundum. An efficiency of the abrasive treatment was assessed by comparison with the properties of surfaces processed with the ion polishing, sheared surface, and natural face of crystal from the viewpoint of reaching the high mechanical damage resistance of the surface.

In the experiments of Mössbauer spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) the morphology and structurization of the carbon phase, the charge state of europium and the dynamic properties of europium bis-phthalocyanine pyrolysed derivatives, including the Debye temperature, were revealed. It was found that the pyrolysis of europium bis-pthalocyanine resulted in the amorphous carbon matrix and nanoscaled graphene clusters both forming turbostratic carbon phase. The europium ions in the charge state Eu³⁺/Eu²⁺ were detected. The data indicated that localization of Eu ions took place between layers of graphenes similar to graphite intercalation compounds. It was shown that an isomeric shift, linewidths and the magnitude of the resonant absorption are essential characteristics of structural transformations at the pyrolysis of rare earth bis-phthalocyanines.

Study of the mechanisms of the solid-state reactions in Sn/Fe/Cu thin films is interesting both from a fundamental point of view and from a view of the importance of emerging intermetallics in the technology of solder joints and thin-film lithium-ion batteries. By the integrated approach, including both X-ray phase analysis and local elemental analysis of the cross-sections of the films, the phase composition and the mutual arrangement of phases were studied, at various stages of the solid-state reaction occurring at different temperatures. The observed sequence of the appearing phases differs significantly from the expected one if the mass transfer took place by a volume diffusion through the forming layers.

The paper shows that upon ignition of the combined gas discharge in the resonator chamber, there appears a double layer with diode properties that consists of layers of positive and negative charges surrounding the workpiece. An increase in the level of microwave power supplied to the chamber leads to a decrease in the equivalent diode resistance in open and closed modes and an increase in the current flowing through the unit. The ions of the process gas (nitrogen or argon) ionized by the microwave field fall on the product surface and diffuse into it as a result of the thermal diffusion process, which hardens the surface layer. The product is heated when a positive bias potential is applied to it by a stream of high-energy electrons arriving at the surface and accelerated to energies of tens and hundreds eV in the discharge acceleration zone. Ion-plasma implantation leads to a significant increase in the strength, wear resistance and corrosion resistance of the surface of the processed product.