A metalens operating at terahertz band is numerically designed. By adjusting the diameters of the pillar array from 25 to 80 μm, the metalens achieves 2π-phase modulation with over 70

This paper shows the results of experimental studies of the influence of oxygen pressure under pulsed laser deposition on the electrophysical parameters of BaTiO3 nanocrystalline films. The elemental composition of BaTiO3 films obtained at different pressures (1x10(-5 )Torr (vacuum) and 1x10(-2 )Torr (oxygen)) was studied by XPS methods. Based on the obtained results, the energy-efficient memristor structures based on BaTiO3 nanocrystalline films were proposed. It was found that 20-nm-thick BaTiO3 films based memristive structure exhibited stable resistive switching effect: HRL/LRS similar to 10 for 100000 cycles. The results obtained can be used to fabricate energy-efficient memristive structures.

At present, interest in silicon carbide is growing, as it has promising properties in some applications: high-temperature electronics, high-frequency power electronics and others. In this regard, it is necessary to produce high quality silicon carbide substrates from which device structures will be created. The proper quality is achieved through the operations, one of which is polishing. Currently, chemical-mechanical polishing method is widely used for this operation, which has some disadvantages: long processing time, high cost and low technical flexibility. A more promising technology for polishing SiC substrates may be electron-beam treatment, which leads to thermal modification of the silicon carbide surface and, as a sequence, to a reduction in roughness. In this paper, a heating model is discussed in relation to a possible polishing mechanism of silicon carbide during its electron-beam treatment, related to the sublimation of silicon formed by the thermal dissociation of SiC. The heating process of a model (rough) silicon carbide surface was modeled in COMSOL Multiphysics® as a solution to the heat conduction problem. The model SiC surface is an array of straight pyramids. The simulation showed that as a result of electron beam heating, the tops of the pyramids are heated more strongly than their bases, which will lead to selective sublimation of silicon and reduction of roughness.

The presented work shows the formation and profiling of nanocrystalline LiNbO3 films obtained by pulsed laser deposition, as well as the influence of the laser pulse repetition rate on the electrical properties, morphology, and growth processes of granular films. The study revealed that the nucleation process in LiNbO3 films can be intentionally altered by increasing the laser pulse repetition rate. When the repetition rate was set to 4 Hz, the resulting film comprised local islands and clusters with a diameter of 118.1 ± 5.9 nm. On the other hand, nanocrystalline films grown at a repetition rate of 10 Hz exhibited a continuous granular structure with a grain diameter of 235 ± 11.75 nm. These findings have the potential to contribute to the advancement of environmentally friendly energy devices utilizing lead-free piezoelectric energy harvesters.

Ash and slag waste from coal combustion is considered as a source of valuable metals. The results of a study of ash and slag waste from CHPPs in Primorye, coal combustion products in the Amur oblast, and some products of ash and slag waste fractionation for gold and scandium content are presented. The concentration levels of these metals were studied by instrumental neutron activation analysis for a preliminary assessment of their possible industrial significance.

We deal with issues related to the formation of ordered silicon nanostructures by processing in a combined fluoride plasma for the formation of monolithic-integrated A3B5 nanostructures. The dependences of the geometric parameters of the formed structures (wall inclination angle, height, and surface roughness) on the power of inductively coupled and capacitive plasma sources were obtained. It is shown that at a structure height of 245.2 nm the roughness was 1.56 ± 0.1 nm, the verticality of the obtained structures varied from 10° to 35°.

In this work, we investigated the effect of plasma-chemical treatment of silicon substrates on the subsequent epitaxial growth of GaAs. It is shown that a change in processing modes did not lead to a strong change in the root-mean-square roughness of the initial silicon surface. It was found that under the same growth conditions GaAs is formed on substrates dif-ferently depending on the silicon treatment mode: from individual crystallites with nanowires to a structure intergrown from individual crystallites. It is shown that a change in the annealing temperature significantly affects the resulting surface morphology.

Here, experimental studies on barium titanate nanocrystalline thin films fabricated by pulsed laser deposition and the influence of the oxygen pressure on the morphological parameters are presented. The average grain size changes from (20.1 & PLUSMN;1.8) nm to (88.2 & PLUSMN;7.9) nm with increasing oxygen pressure from 1x10-5 Torr to 1x10-2 Torr. The effect of plasma treatment on the parameters of BaTiO3 nanocrystalline thin films was studied. It was found that the formation of whisker-like structures is preferred for BaTiO3 when the power of inductively coupled and capacitive plasma sources increases. The results can be applied to the design and development of technological processes for promising lead-free energy converters, eco-friendly energy devices and memristive structures developed based on pulsed laser deposition.

The formation of metal-bearing coalfields of the Raichikhinskoe deposit in the conjugation zone of distributive provinces of the Bureya uplift and coal-accumulation areas of the Zeya–Bureya sedimentary basin was studied. It was established that it occurred under conditions of the successive extraction of ore components from weathering crusts of the Bureya uplift, transportation, and unloading in the paleodelta of the Bureya River. These processes proceeded synchronously with volcanic activity in the Sikhote-Alin orogenic belt, which is associated with the supply of volcanic ash. The association of these events made it possible to distinguish two types of enrichment of the Raichikha coals in rare earth elements and yttrium (REY): terrigenous with the supply of REY by surface waters and combined terrigenous volcanogenic associated with the shedding and leaching of acidic and alkaline volcanic ash. The cerium group lanthanides predominate in coals and their combustion products. The largest fraction of REY was contained in fly ash (0.11% on a total weight basis). The mechanisms of accumulation of ore components at the stage of peat deposits are considered from the standpoint of the localization of trace ore components as clastogenic mineral forms and under the conditions of interaction of ore solutions with the organic environment of peat bogs. The quality of REY was assessed, and the most enriched sections of the Verkhnii layer were identified. Prospects for the extraction of lanthanides from coal are considered from the standpoint of the possible recovery of a number of rare, nonferrous, and noble metals in this process.

Precision measurement is gradually shifting from laboratories to real-world environments and production platforms to meet the increasing requirement of intelligent manufacturing. Metasurfaces, 2D engineered artificial interfaces, have emerged as candidates to replace traditional refractive lenses.

The formation of metal-bearing coalfields of the Raichikhinskoe deposit in the conjugation zone of distributive provinces of the Bureya uplift and coal-accumulation areas of the Zeya–Bureya sedimentary basin was studied. It was established that it occurred under conditions of the successive extraction of ore components from weathering crusts of the Bureya uplift, transportation, and unloading in the paleodelta of the Bureya River. These processes proceeded synchronously with volcanic activity in the Sikhote-Alin orogenic belt, which is associated with the supply of volcanic ash. The association of these events made it possible to distinguish two types of enrichment of the Raichikha coals in rare earth elements and yttrium (REY): terrigenous with the supply of REY by surface waters and combined terrigenous volcanogenic associated with the shedding and leaching of acidic and alkaline volcanic ash. The cerium group lanthanides predominate in coals and their combustion products. The largest fraction of REY was contained in fly ash (0.11% on a total weight basis). The mechanisms of accumulation of ore components at the stage of peat deposits are considered from the standpoint of the localization of trace ore components as clastogenic mineral forms and under the conditions of interaction of ore solutions with the organic environment of peat bogs. The quality of REY was assessed, and the most enriched sections of the Verkhnii layer were identified. Prospects for the extraction of lanthanides from coal are considered from the standpoint of the possible recovery of a number of rare, nonferrous, and noble metals in this process.

At present, the focused ion beam method is an effective technique for nanoscale profiling of a solid surface and prototyping of micro- and nanoscale structures. The article reveals the results of experimental studies on improving the accuracy and resolution of nanoscale profiling of the surface of solids with a focused ion beam. Investigations of the regularities of the influence of the focused ion beam current, beam dwell time and overlap on the parameters of nanoscale structures and the surface profile have been carried out. The influence of the FIB parameters on the deviation of the structure profile from the specified by the template was estimated. Experimental studies have been carried out to determine the influence of the direction of scanning of the ion beam by the template on the magnitude of the error that occurs when the structure of the graphic template is transferred to the substrate. The optimal relationships between the FIB current and the dimensions of the structures being formed have been determined, thus making it possible to ensure the highest accuracy and rate of formation of nanoscale structures. The results can be used to optimize the choice of the ion-beam milling parameters to achieve the maximum accuracy of reproduction of the given sizes of structures.

This paper reports the impact of the laser pulse repetition frequency on growth processes, morphological and electro-physical parameters of nanocrystalline LiNbO3 thin films obtained by the pulsed laser deposition technique. It was found that the nucleation process in LiNbO3 films could controllably change by increasing the laser pulse repetition frequency. The film obtained at the repetition frequency of 4 Hz consists of local islands and clusters with a diameter of 118.1 ± 5.9 nm. Nanocrystalline films, grown at the repetition frequency of 10 Hz, possess a continuous granular structure with a grain diameter of 235 ± 11.75 nm. Achieved results can be used for the development of promising “green” energy devices based on lead-free piezoelectric energy harvesters.

In this paper, the films of lead zirconate-titanate formed by the method of high-frequency reactive plasma sputtering in oxygen are studied. The films have a thickness of 610-660 nm and a developed relief with a predominant number of protrusions with a height of 100-300 nm. It is shown by the methods of X-ray phase analysis and piezoelectric force microscopy that the PZT crystallites are located on the surface of the protrusions. The piezoelectric strain coefficient value is 2,73+0,44 pm/V. The formed PZT films can be used in 3D elements of nanopiezotronics (memory elements, sensors of mechanical influences, energy harvesters). Copyright (C) 2022 Elsevier Ltd. All rights reserved.

The paper shows the experimental results of the substrate temperature effect on the morphological and electro-physical parameters of nanocrystalline BaTiO3 films fabricated by pulsed laser deposition. It was found increasing in the substrate temperature from 300 °C to 600 °C results in decreasing in surface roughness from (6.1±0.6) nm to (0.8±0.1) nm and increasing in the films grain size from (39.1±3.1) nm to (212.1± 17.2) nm. Increasing in the substrate temperature leads to a change in electro-physical parameters: the concentration of charge carriers increases from (1.85±0.16)×1013 cm-3 to (2.77±0.25)×1013 cm-3, the mobility of charge carriers decreases from (10.1±0.9) cm2/(V·s) to (7.2±0.6) cm2/(V·s), and the resistivity of the films changes insignificantly from (3.4±0.2)×103 Ω·cm to (3.1±0.2)×103 Ω·cm under increase in the temperature from 300 °C to 600 °C. The obtained results make it possible to get BaTiO3 films with target parameters, which can be used to develop promising lead-free energy harvesters for alternative energy devices.

In order to consider quantum dots as single objects and to use them in modern electronic and photonic devices, they must be well-isolated from each other and have an appropriate size and structural quality. This is a big challenge that is difficult to achieve with traditional technological methods, such as the Stranski-Krastanov growth mechanism. In this paper, we present a novel droplet epitaxial technique for the fabrication of small-sized (similar to 25 nm) InAs/GaAs nanostructures with a low surface density (<1.10(8) cm(-2)). To achieve this result, we develop a growth method based on two-stage crystallization in the arsenic flux. At the first stage, the droplet size is reduced by spreading the droplet material over the surface due to the diffusion decay of droplets in an ultra-low arsenic flux. At the second stage, crystallization is carried out in a large arsenic flux while heating the substrate in order to fix the size and shape of nanodroplets and prevent them from further decaying. We demonstrate that the size dispersion of nanostructures is small and the process is well-reproducible. Thus, the presented approach makes it possible to obtain low-density quantum dots with an ultra-small size required for advanced optical applications.

This paper presents the results of experimental studies of the modes of formation of nanosized structures on the surface of a silicon substrate by the method of focused ion beams (FIB). The regularities of the effect of the ion beam current, accelerating voltage, and radiation dose on the surface morphology of nanoscale structures are determined. The modes under which the effects of implantation swelling (structure height up to 3 nm) and etching (structure depth up to 8 nm) manifest themselves are determined. The average roughness of the resulting structures varies from 0.13 to 0.24 nm. The results can be used in the development of technology for manufacturing instrument structures in nanoelectronics and nanophotonics.

In this paper, we present a study of the effect of the silicon substrate modification by focused ion beams on subsequent growth of GaAs layers by molecular beam epitaxy. We demonstrate that when samples exposed to the ion irradiation at various accelerating voltages and ion beam passes are annealed in the absence of the arsenic flux, an increase in the depth of the modified Si substrate areas occurs. At the same time, crystallization of gallium accumulations during annealing in the arsenic flux leads to the filling of holes formed during the ion bombardment. We reveal that the growth of GaAs on substrates with areas modified at an accelerating voltage of 30 kV and subjected to subsequent annealing in the arsenic flux at a temperature of 600 o C is accompanied by the formation of nanowires, the density of which increases within areas with a large number of ion beam passes. The results of the conducted research can be used for the development of technological approaches to the formation of GaAs epitaxial layers on Si substrates. Keywords: molecular beam epitaxy, monolithic integration, gallium arsenide, silicon, focused ion beams.

In this work, we investigated the influence of the focused ion beams modification modes of the Si substrate local areas on the subsequent growth of GaAs layers by the molecular beam epitaxy. It was found that the crystallization of Ga droplets upon annealing in an arsenic flow does not lead to a significant change in the surface morphology. It was also found the growth of GaAs on substrates with areas modified at an accelerating voltage of 30 kV and subjected to subsequent annealing at a temperature of 800°C results in the formation of nanowires.

This paper presents the results of atomic force microscopy and Raman spectroscopy studies of the effect of high-temperature annealing on the height/depth parameters of silicon areas modified by a focused ion beam. It is shown that the focused ion beam treatment with 5 beam passes leads to swelling of the surface of the modified silicon areas. It was found that the depth of the focused ion beam modified area is different after annealing at 600 and 800 degrees C. An increase in the number of passes in both cases led to an increase in the depth of the focused ion beam modified areas. The results of studies of Raman spectroscopy showed that with an increase in the number of passes, a decrease in the crystallinity of silicon occurs. It is also shown that annealing of such regions leads to the restoration of crystallinity upon annealing at 600 degrees C and almost complete restoration of crystallinity at 800 degrees C.