Carbonaceous matter (CM) with an unusual two-phase composite structure has been discovered in the vicinity of deep fault intersections in Kozhim River Valley, Subpolar Urals. This CM predominantly comprises sp2 carbon, characterized by turbostratic stacks of distorted graphene layers measuring 20-30 nm in size. Within this turbostratic matrix, isolated rounded inclusions of a polycrystalline nanodiamond phase, ranging from 100 to 500 nm in size, have been identified. Notably, the crystallites with slightly distorted diamond structure exhibit a rare rod-like morphology, with a length of about 3 nm and a transverse diameter of approximately 0.5-0.7 nm. Such crystallites complement the wide range of carbon structures in natural materials. The turbostratic phase genesis can be compared with the artificial pyrocarbon deposition. The source of the CM can be interpreted as a deep mantle fluid consisting of simple hydrocarbon gases and hydrogen sulfide. The low-pressure, low-temperature host rocks, combined with the turbostratic phase, do not align with the typical conditions required for diamond structure formation. Consequently, we propose that the nanodiamond phase originated from cavitation events during the rapid ascent of the deep mantle fluid. This report represents the first known instance of a geological composite material featuring of pyrolytic turbostratic carbon and a nanodiamond phase, and not associated with impact events (astroblemes and meteorites).

Quantification of ion-induced disorder and study of irradiation damage mechanisms, particularly the formation of nanoclusters by implanted inert gas ions, remains a challenging task in various ion beam applications including modern focused ion beam technology. The crystalline silicon substrate was bombarded by 5 and 8 keV xenon ions, and the damaged layers were studied using plan-view and cross-sectional transmission electron microscopy. The formation of xenon clusters in the amorphized layer was established, and their size distribution was evaluated using image processing techniques, the depth distribution of the implanted ions was determined using energy dispersive X-ray microanalysis. Cross-correlation analysis of high-resolution transmission electron microscopy (HRTEM) images was applied to quantify the width of the transition region between crystalline silicon and an amorphous layer, as well as the amorphous layer thickness. Molecular dynamics simulations demonstrated the formation of xenon clusters and quantitatively reproduced the experimentally obtained depth distribution of implanted ions. HRTEM images simulated using the obtained atomic positions were in good agreement with the experimental micrographs. Thermal relaxation was performed after ion bombardment to minimize the discrepancies between the experimental and simulated widths of the transition region.

Heterostructures with an active region based on GaAs/Ge/GaAs layers are of interest for creating terahertz devices and topological insulators. The optical and electrical properties of such devices depend, to a great extent, on the conditions of their synthesis. In this work, the structure of GaAs layers in GaAs/Ge/GaAs heterostructures grown on a GaAs(001) substrate by molecular-beam epitaxy under process conditions providing a 90° rotation of the crystal lattices of the upper and lower GaAs layers in samples of one type and no rotation in samples of the other type is examined. The synthesized heterostructures are studied by transmission electron microscopy and electron-diffraction analysis using thin cross-sectional foils prepared by the focused-ion-beam method. It is found that the GaAs/Ge/GaAs layers in samples of both types have a high crystal quality, but stacking faults and antiphase domains are formed in the GaAs layers located above the Ge layer. The relative orientation of the upper and lower GaAs layers in GaAs/Ge/GaAs is identified by comparing the intensity distributions in the disks 002̅ and 002 in the diffraction patterns obtained by convergent-beam electron diffraction. It is demonstrated by simulating the patterns that the orientation of the sample along the [310] zone axis is optimum for detecting differences between the diffraction patterns on pseudo-forbidden disks 002̅ and 002. The experimental diffraction patterns obtained under such conditions confirm the identical orientation of the crystal lattices of the upper and lower GaAs layers in samples of one type and the rotation of the lattices of these layers by 90° about the [001] direction in the samples of the other type.

The focused-ion-beam method is used to modify the surface and form of structures on substrates of almost any material. The significance of silicon and silicon dioxide for modern nanotechnologies calls for comparative analysis of their sputtering by the focused-ion-beam method under identical experimental conditions. In this work, the processes of the sputtering of single-crystal silicon and thermal silicon dioxide are compared. Cross sections of depressions of two types, with a low and high aspect ratio, are studied by scanning electron microscopy. It is established that, in both materials, the depressions of both types have almost the same shape, despite significant differences in the physical properties of silicon and silicon dioxide. Structure formation is simulated by the level-set method using known experimental dependences of the sputtering yields. To take into account sputtering by reflected ions, their angular and energy distributions are calculated using the Monte Carlo method. These dependences and the rates of sputtering of silicon and silicon dioxide by reflected ions established on their basis are almost identical, which indicates the similarity of the sputtering mechanisms for these materials. Superposition of the calculated profiles of the formed depressions onto their cross-sectional images makes it possible to establish that the simulation adequately describes the shape of the resulting structures with a low aspect ratio for both materials. For the structures with a high aspect ratio, satisfactory agreement between the simulation results and experimental data is established for the single-crystal silicon sample; for depressions in silicon dioxide, the discrepancy in the depth of the calculated and experimental profiles is 10

For the creation of modern spintronic devices, heterostructures based on the spin gapless semiconductor CoFeMnSi are of interest. The characteristics of such devices are determined by the structural and magnetic properties of the CoFeMnSi layer. The development of a technology for the production of defect-free thin-film layers of CoFeMnSi is an urgent task at present. The paper considers thin single-crystal CoFeMnSi films grown on the surface of a MgO(100) substrateby the pulsed laser deposition method. Optimization of the technological parameters for the production of CoFeMnSi films is carried out. It is shown that by selecting the optimal values of the MgO(100) substrate temperature, the target–substrate distance, and the energy and frequency of the pulsed laser radiation, CoFeMnSi films can be produced in the island or layer-plus-island growth modes. It is found that for to grow CoFeMnSi films in the layer-by-layer mode, it is necessary to introduce two-minute pauses during the formation of each new film layer, the use of which makes it possible to grow atomically smooth single-crystal CoFeMnSi films up to 20 nm thick. Electron microscopic studies and diffraction analysis of cross-sectional samples of the films grown on the substrate demonstrate that they have a perfect cubic crystalline structure. The position of the reflections in the diffraction pattern indicates that the cubic unit cells of the CoFeMnSi film (space group F4̅3m ) and the MgO(100) crystal are rotated relative to each other by an angle of 45° around the MgO[001] direction, thereby ensuring their alignment along the CoFeMnSi(202) and MgO(020) planes. The obtained results can be used for the production of multilayer heterostructures and devices based on them.

Germanium-cobalt-indium (Ge-Co-In) nanostructures are a promising material for negative electrodes of lithium- ion batteries aimed for arctic exploitation. Electrochemical impedance spectroscopy was used for a detailed study of the interaction of Ge-Co-In nanostructures with lithium in a temperature range from -35 to +20 degrees C. The discharge capacity at temperatures of 20, 0, -10, -20, and -35 degrees C amounted to 1400, 1228, 1040, 907, and 793 mAh g-1, respectively. The impedance spectra measured at various lithiation degrees were found to differ but insignificantly whereas temperature variation resulted in notable changes in the spectra. A normalized charge transfer resistance for Ge-Co-In nanostructures was significantly (more than an order of magnitude) less than for Ge-In nanowires (obtained by the same method, but without the addition of cobalt salt into the electrolysis solution). It is this difference in charge transfer resistance that can explain the difference in the shapes of the impedance spectra for both objects. Also, in contrast to data for Ge-In nanowires, the dependences of the lithium diffusion coefficient in Ge-Co-In nanostructures on potential had a clearly defined minimum. The lithium diffusion coefficient in Ge-Co-In nanostructures slightly exceeded that in Ge-In nanowires, and the activation energy of lithium diffusion in Ge-Co-In nanostructures was marginally less than in Ge-In nanowires.

Using photoluminescence and Raman spectroscopy, as well as high-resolution transmission microscopy and X-ray diffraction, germanium nanowires obtained by cathodic deposition from an aqueous solution of germanium dioxide were studied during their annealing by a laser at 720 °C under ambient conditions. It is established that the dynamics of Raman and photoluminescence spectra are related to the oxidation of wires during such annealing. The study showed that vacuum annealing of as-grown nanowires at 600 °C for 30 min suppresses laser high-temperature germanium oxidation. The observed effect is associated with the saturation of vacancies in the surface germanium suboxide with indium atoms used as a catalyst in the formation of nanowires.

Understanding the formation and evolution of arrays of metallic nanoparticles is a very important task as they are increasingly used in various devices. In this work, we used HRTEM mode for continuous in-situ observations of the evolution of Ag and Au nanoparticle arrays with an average size of similar to 4 nm, formed on the surface of amorphous carbon by vacuum-thermal evaporation, under the influence of a microscope electron beam without any other energetic influence. Our studies show that electron beam exposure induces a process of nanoparticle coalescence for Au and simultaneous coalescence and vaporization for Ag. As a result, the evolution of Ag and Au nanoparticle arrays has different mechanisms. In the case of Ag, the aggregation of nanoparticles occurs through the gas phase by the Ostwald ripening mechanism. In the case of Au, it was found that the aggregation of nanoparticles depends on their mutual crystalline orientation, resulting in the realization of mechanisms through bridge formation or through jumping. The influence of the crystalline orientation of the nanoparticles on the coalescence mechanism was confirmed by molecular dynamics simulations. MD simulations revealed that it is most favorable for coalescence if the densely packed planes of neighboring nanoparticles have a perpendicular arrangement in space.

The structural studies of two-dimensional (2D) van der Waals heterostructures and understanding of their relationship with the orientation of crystalline substrates using transmission electron microscopy (TEM) presents a challenge in developing an easy-to-use plan-view specimen preparation technique. In this report, we introduce a simple approach for high-quality plan-view specimen preparation utilizing a dual beam system comprising focused ion beam and scanning electron microscopy. To protect the atomically thin 2D heterostructure during the preparation process, we employ an epoxy layer. This layer serves as a protective barrier and enables the creation of a TEM specimen comprising a thin substrate fragment with an overgrown 2D structure covered by a thin, electron-transparent epoxy layer. The coexistence of both 2D layers and substrate is essential for investigating the relative crystallographic orientations between the grown 2D structures and the substrates. The thickness of the specimen is monitored using low-voltage scanning electron microscopy. We apply this technique to prepare plan-view specimens of 2D germanium-antimony-telluride (GST) on Si and hexagonal boron nitride (h-BN)/epitaxial graphene (EG) heterostructures grown on 6H-SiC substrates. The grain-like atomic structure observed in the 2.2 nm thick GST layer on Si substrate provides evidence of the mosaicity of GST during the early stages of epitaxial growth. H-BN/EG on 6H-SiC structural studies indicate a rotation of h-BN/EG around the 6H-SiC[0001] axis by an angle of 30°. The observed BN particles with sizes in the nanometer range on top of the sample have the wurtzite lattice type and random orientation. The developed specimen preparation technique offers a powerful tool for TEM studies of atomically thin layers on crystals. Its simplicity and ability to provide valuable insights into the in-plane relationships between 2D structures and crystalline substrates make it a promising complement to grazing incident X-ray diffraction.

The evolution of a multilayer sample surface during focused ion beam processing was simulated using the level set method and experimentally studied by milling a silicon dioxide layer covering a crystalline silicon substrate. The simulation took into account the redeposition of atoms simultaneously sputtered from both layers of the sample as well as the influence of backscattered ions on the milling process. Monte Carlo simulations were applied to produce tabulated data on the angular distributions of sputtered atoms and backscattered ions.Two sets of test structures including narrow trenches and rectangular boxes with different aspect ratios were experimentally prepared, and their cross sections were visualized in scanning transmission electron microscopy images. The superimposition of the calculated structure profiles onto the images showed a satisfactory agreement between simulation and experimental results. In the case of boxes that were prepared with an asymmetric cross section, the simulation can accurately predict the depth and shape of the structures, but there is some inaccuracy in reproducing the form of the left sidewall of the structure with a large amount of the redeposited material.To further validate the developed simulation approach and gain a better understanding of the sputtering process, the distribution of oxygen atoms in the redeposited layer derived from the numerical data was compared with the corresponding elemental map acquired by energy-dispersive X-ray microanalysis.

Test structures in the form of rectangular boxes fabricated on thermal silicon dioxide substrates under normal and oblique ion bombardment using the focused ion beam technique were studied by transmission electron microscopy and energy-dispersive X-ray microanalysis. The experimentally obtained depth distribution profiles for gallium atoms, as well as the sputtering yields, were compared with the results of Monte Carlo simulations. Calculations were carried out using standard continuous and discrete-continuous models for the surface binding energy of atoms in silicon dioxide. For the normal incidence of the ion beam, based on minimizing the value of the R-factor, which characterizes the agreement between the calculated and experimental data, the optimal values of the parameters of the discrete-continuous model were found, which turned out to be close to the values used in the continuous model. It is shown that the obtained parameters make it possible to simulate silicon dioxide sputtering with acceptable accuracy at ion beam incidence angles of 15° and 30°. However, at a grazing incidence angle of 80°, significant differences arise between the experimental and calculated profiles of the concentration of gallium atoms implanted in silicon dioxide.

The methods of transmission electron microscopy and high-resolution electron microscopy, used to study multilayer heterocomposites, have limitations in resolution, do not allow for the effective investigation of amorphous materials and require the analysis of many local areas in the case of samples consisting of individual crystallites. In this work, we investigate a multilayer heterocomposite, which is a phase-shift photomask consisting of layers of nanoscale thickness on the surface of a glass substrate. Focused-ion-beam methods are used to study a thin foil of cross and longitudinal sections. To identify the structure and determine the composition of the layers, the methods of transmission electron microscopy and energy-dispersive X-ray microanalysis are used. The analysis of cross-sectional foils prepared using standard approaches allows visualization, thickness measurements, and determination of the layer compositions. It is shown that on the SiO2 substrate an amorphous layer of Mo0.06Si0.31N0.63 93 nm thick is formed, which is successively coated with polycrystalline layers of Cr0.56N0.44, Cr0.74C0.06N0.2, and Cr0.4N0.26O0.3 with thicknesses of 22, 37, and 8 nm, respectively. A thin foil with a planar cross-section, prepared at a slight inclination to the surface of the photomask, makes it possible to form sections of all layers with dimensions sufficient for their study by electron microdiffraction. The performed electrographic analysis confirmed the amorphous structure of the substrate and Mo0.06Si0.31N0.63 layer, and also showed that polycrystalline layers of Cr0.56N0.44, Cr0.74C0.06N0.2, and Cr0.4N0.26O0.3 formed by crystallites with a cubic lattice and parameters of 3.92, 4.18, and 4.12 Å, respectively.

We analyzed main structural models of sp2 carbon with a structure similar to glassy carbon from the point of view of impedance spectroscopy in the range from hertz frequencies to 15 MHz. We used samples of natural carbon (shungites, anthraxolites) with a structure and properties close to synthetic glassy carbon. The impedance spectroscopy results were compared to high-resolution transmission electron microscopy (HRTEM) images, which revealed a complex nanoscale structure including stacks of misoriented graphene layers, multilayer ribbons, and closed fullerene-like structures. The high locality of the HREM method often does not allow identifying the predominant nano-sized structure if two or more types of structural elements are observed in one sample. Using impedance spectroscopy, we found samples with an inductive type of resistance indicating predominant extended and tortuous elements (ribbons, fibrils), as well as samples with a capacitive type of resistance with a significant predominance of nano-sized stacks of graphene layers with impurities/dielectric gaps and micropores.

We analyzed main structural models of sp 2 carbon with a structure similar to glassy carbon from the point of view of impedance spectroscopy in the range from hertz frequencies to 15 MHz. We used samples of natural carbon (shungites, anthraxolites) with a structure and properties close to synthetic glassy carbon. The impedance spectroscopy results were compared to high-resolution transmission electron microscopy (HRTEM) images, which revealed a complex nanoscale structure including stacks of misoriented graphene layers, multilayer ribbons, and closed fullerene-like structures. The high locality of the HRTEM method often does not allow identifying the predominant nano-sized structure if two or more types of structural elements are observed in one sample. Using impedance spectroscopy, we found samples with an inductive type of resistance indicating predominant extended and tortuous elements (ribbons, fibrils), as well as samples with a capacitive type of resistance with a significant predominance of nano-sized stacks of graphene layers with impurities/dielectric gaps and micropores.

Revealing the regularities of interaction of accelerated ions with an irradiated material based on the Monte Carlo simulation contributes to the efficient application of focused ion beam technique in modern nanotechnologies. The correctness of the calculation results depends on the model chosen and the parameters determining the surface binding energy (SBE) of sputtered atoms. In this work, the SBE has been determined within the discrete–continuous model, which makes it possible to consider the formation of gallium precipitates during irradiation of a silicon substrate with gallium ions. To compare the simulation results with the experimental data on material sputtering by a focused ion beam, two types of rectangular boxes have been prepared. The structures of the first type were formed at the same dose, close to 5 × 10 17 cm –2 (corresponding to the steady-state sputtering regime), at accelerating voltages of 8, 16, and 30 kV. The structures of the second type were formed at an ion energy of 30 keV and doses of 2.5 × 10 16 , 5 × 10 16 , and 1 × 10 17 cm –2 . The box cross sections were investigated by transmission electron microscopy. The sputtering yield and depth distribution profiles of gallium atoms, calculated in the SDTrimSP 5.07 software package, were compared with the experimental data using the R factor. Two sets of values have been established for the variable parameters: the SBE of gallium atoms and the α 1 parameter of the discrete–continuous model. The first set describes the experimental data with acceptable accuracy for a small number of implanted gallium atoms, which is implemented for low ion doses, as well as for a beam energy of 8 keV and a dose of 5 × 10 17 cm –2 . The second set is optimal for describing the ion beam interaction with the substrate at ion energies of 16 and 30 keV under steady sputtering conditions.

Silver is one of the most promising nanomaterials for plasmonic applications, but it has become clear that the shape and internal symmetry of nanoparticles can significantly affect the scattering and absorption of light waves. Therefore, for the use of silver nanoclusters in plasmonic applications, it is very important to determine the conditions of stability of the structure and form of Ag nanoparticles. To this end high-resolution electron microscopy was used to examine initial and annealed arrays of silver nanoparticles with diameters ranging from 0.8 to 9.4 nm, formed on a carbon substrate by vacuum thermal evaporation. It was found that small Ag nanoparticles (D < 3.0 nm) have almost perfect FCC structure, while nanoparticles of larger diameter unexpectedly have predominantly icosahedral or decahedral facets. To explain this contradiction from the perspective of standard crystallographic theory, molecular dynamics simulations using the TB-SMA potential were conducted to study the stability limits of structural modifications of silver nanoclusters of similar diameters, and possible atomic rearrangement mechanisms that could lead to such experimental results were found. Based on the results of the computer analysis, conclusions were drawn about the technological possibilities of creating the desired crystal structure of Ag nanoparticles when preparing SERS substrates.

The level set method was generalized for simulating the evolution of the surface of multilayer substrates under focused ion beam irradiation. For a correct description of such process the calculations took into account the sputtering yield angular dependences, the densities of the irradiated materials and it was considered that sputtered atoms can escape from different layers of the substrate. Comparison of the calculation results with experimental data for test structures formed in a two-layer silicon dioxide–crystalline silicon substrate showed that the developed simulation method makes it possible to predict the shape of structures fabricated by a focused ion beam with good accuracy.

The level set method was generalized for simulating the evolution of the surface of multilayer substrates under focused ion beam irradiation. For a correct description of such process the calculations took into account the sputtering yield angular dependences, the densities of the irradiated materials and it was considered that sputtered atoms can escape from different layers of the substrate. Comparison of the calculation results with experimental data for test structures formed in a two-layer silicon dioxide-crystalline silicon substrate showed that the developed simulation method makes it possible to predict the shape of structures fabricated by a focused ion beam with good accuracy. Keywords: Focused ion beam, sputtering, level set method.

A nanostructured n-type thermoelectric (TE) material based on lead telluride (PbTe) (doped with 0.2 wt% PbI2 and 0.3 wt% Ni) was fabricated and investigated. Fabricating technology included the synthesis of PbTe by direct alloying of components, the grinding of synthesized PbTe in a planetary ball mill, and the compaction of the nanopowders by spark plasma sintering (SPS). Complex investigations of the structure and composition of powders and nanostructured PbTe and the thermoelectric parameters of nanostructured PbTe were carried out. The particle sizes of the powders ground for 20 and 60 min varied from 36 to 378 nm and from 29 to 210 nm, respectively. The maximum value of dimensionless thermoelectric figure of merit (ZT) = 1.35 for nanostructured PbTe was obtained for a sample compacted by SPS after grinding synthesized PbTe for 60 min, which is 14% higher than ZT for TE material obtained by hot pressing. Recrystallization of crystalline particles during SPS leads to an increase of the grain sizes in nanostructured PbTe by approximately 3 times and the elimination of microdeformations that appear during grinding. Analysis of the temperature dependencies of thermoelectric parameters showed that an increase in ZT for nanostructured PbTe is achieved due to the decrease in lattice thermal conductivity.(c) 2023 Elsevier Ltd. All rights reserved.

Van der Waals (vdW) epitaxial growth of large-area and stable two-dimensional (2D) materials of high structural quality on crystalline substrates is crucial for the development of novel device technologies. 2D gallium monochalcogenides with low in-plane symmetry stand out among the layered semiconductor materials family for next-generation optoelectronic and energy conversion applications. Here, we demonstrate the formation of large-area, single crystal and optically active 2D monoclinic gallium telluride (m-GaTe) on silicon substrate via rapid thermal annealing induced phase transformation of vdW epitaxial metastable hexagonal gallium telluride (h-GaTe). Stabilization of multilayer h-GaTe on Si occurs due to the role of the first layer symmetry together with efficient GaTe surface passivation. Moreover, we show that the phase transformation of h-GaTe to m-GaTe is accompanied by the strain relaxation between Si substrate and GaTe. This work opens the way to the fabrication of single-crystal 2D anisotropic semiconductors on standard crystalline wafers that are difficult to be obtained by epitaxial methods.