Here, we report on functional coating of a commercial Celgard (R) PP2075 polypropylene separator by synthetic 1:1 Mg-phyllosilicate to enhance the performance and stability of lithium-ion batteries. The research focuses on addressing the key limitations of conventional separators, such as low melting point, hydrophobic surface, and mechanical strength. We developed a composite coating consisting of magnesium phyllosilicate nanoparticles (curved plates and nanoscrolls) and PVDF binder, applied to the separator via a blade-coating technique. The synthesized Mg3Si2O5(OH)4 phyllosilicate exhibited a high specific surface area of 211 m2/g and a hydrophilic nature due to the presence of OH-groups. The composite separator demonstrated an increase in tensile strength by 30.9 MPa and elongation at break by 17.1 %. Electrochemical evaluation revealed that while the ionic conductivity slightly decreased to 0.43 mS/cm, the composite separator provided more uniform Li+ ions distribution and better resistance to lithium dendrite formation. Li/LiCoO2 coin cells with the composite separator exhibited superior cycling stability, retaining 88 % of initial capacity after 100 cycles compared to 73 % for cells with the bare separator. The study demonstrates that the separator, modified by synthetic phyllosilicate, offers a promising solution for improving the safety and longevity of lithium-ion batteries, particularly in applications requiring stable long-term performance.

In the last decades, transition elements doping of phyllosilicates greatly expanded the range of their applications including adsorption, catalysis, and composite materials manufacturing. The preparation of such materials and their subsequent operation often involves continuous thermal treatment. However, information on the thermal behavior of transition metal -doped phyllosilicates is still lacking. Here this gap was filled for the case of synthetic (CoxMg1-x)3Si2O5(OH)4 (x = 0.2, 0.4, 0.6, 0.8 and 1) phyllosilicate nanoscrolls treated in air, Ar and Ar-H2 gas flows in the 25-1000 degrees C range. Presence of Co2+, which could be both oxidized and reduced, initiated different phase changes depending on the atmosphere type. Two principal transitions occurred during heating in Ar flow. The first transition was related to the formation of sepiolite-like phase with partial amorphization (after 400 degrees C). The second transition was the crystallization process of orthosilicate (after 700 degrees C). These two main processes were accompanied by the appearance of Co3O4 when heated in air atmosphere (at about 300 degrees C) or the formation of Co0 nanoparticles when heated in Ar-H2 atmosphere (after 400 degrees C). The study revealed several morphological features during heat treatment in various gaseous media. First, Co0 nanoparticles oxidized and covered themselves with an oxide shell if they were not stabilized in the phyllosilicate matrix. Second, the metal tended to fill the nanoscrolls inner channel, forming extended nanorods. Finally, double -walled phyllosilicate nanotubes demonstrated exceptionally high thermal stability, conserving their morphology even up to 800 degrees C.

This work presents for the first time the possibility of reducing and tuning the work function of field emission cathodes coated with metal oxides by changing the chemical composition of...

Initial stage of precipitate formation during post-growth annealing of nonstoichiometric GaAs and GaAs0.97Sb0.03 grown by low-temperature (150°C) MBE on GaAs (001) substrate with intermediate growth interruption and simultaneous heating up to 250°C was studied by transmission electron microscopy. Short-term intermediate heating despite the low temperature was revealed to result in the precipitation of larger particles during subsequent post-growth annealing compared to the material not subjected to such heating. This effect is explained by the huge concentration of excess arsenic in LT-GaAs and LT-GaAs0.97Sb0.03 grown at 150°C, enhanced diffusion due to the high concentration of nonequilibrium gallium vacancies, and non-threshold nucleation.

The effect of lattice relaxation instability (martensitic transition) on piezoelectric fields (EPE) in spontaneously ordered GaInP2/GaAs epitaxial layers was demonstrated using scanning Kelvin probe microscopy in combination with electron microscopy and optical spectroscopy measurements. The transition manifests itself in the dependence of the surface potential of the epi-layer on the mechanical (cleavage) and thermal (annealing) impacts. This is associated with a switching of the crystal lattice between relaxed and strained martensitic states, corresponding to a change in EPE in the epi-layer. The measured surface potential values (0.2–2.4 V) correspond to EPE within ±100 kV/cm and a strong decrease in |EPE| with increasing layer thickness, indicating the pinning of the Fermi level and piezoelectric doping. Our results open up the prospects for using spontaneously ordered semiconductor alloys to control electronic states in semiconductor nanostructures by controlling their piezoelectric fields.

The properties of multilayer (up to 80 layers) nanoperiodic (period up to ~12 nm) Al 2 O 3 /Ge and Al 2 O 3 /Si/Ge/Si systems annealed in a nitrogen atmosphere at temperatures from 700 to 900°C are studied using transmission electron microscopy, X-ray techniques of photoelectron spectroscopy, diffractometry, and reflectometry, and optical methods of photoluminescence and Raman scattering. In Al 2 O 3 /Ge samples annealed at 700°C, the formation of Ge nanocrystals with a size of ~3 nm is detected, which disappear at 800–900°C, when nanocrystals of the Al 6 Ge 5 semiconductor phase of large size (>100 nm) grow. The introduction of separating layers of Si (Al 2 O 3 /Si/Ge/Si) leads to the formation of nanocrystals of the SiGe x alloy at a temperature of 800°C, above which the size of the crystallites of this phase is about ~3–4 nm. The data obtained using X-ray techniques are in good agreement with the results of high-resolution transmission electron microscopy and Raman spectroscopy. In the Al 2 O 3 /Ge samples, photoluminescence is observed at room temperature at ~2.1 eV, and in the Al 2 O 3 /Si/Ge/Si samples, there is an additional luminescence peak at ~1.4 eV. Hydrogenation of the samples by annealing in a hydrogen atmosphere at 500°C enhances the luminescence intensity.

The structure of epitaxial films of the GaInP solid solution, in which ordering occurs, has been studied by transmission electron microscopy. The films have been grown by metalorganic vapor-phase epitaxy on GaAs(001) substrates near the half-composition point. The dark-field images obtained using superstructure reflections for cross-sectional and plane-view samples of films have been analyzed. The morphology and relative spatial arrangement of ordered domains have been determined. The phenomenon of spontaneous self-organization of regions with CuPt–B+ and CuPt–B– ordering near the surface has been discovered, while in the bulk of the film, the domains are uniformly distributed and overlap. The effect of spatial separation of domains is attributed to the misfit stress relaxation in the growing epitaxial layer, which changes the surface topology.

We studied the process of obtaining nanostructured halloysite by varying the parameters for cre-ating the initial composition. The initial composition was synthesized by co-hydrolysis of (C3H7O)3Al , (C2H5O)4Si in the C6H14-NH3 center dot H2O system. Aluminum hydrosilicate with the composition Al2Si2O5(OH)4 was synthesized under hydrothermal conditions (220 degrees C, 2 MPa, 96 h). Particles of plate-like morphology with av-erage length 100 - 200 nm and 60 nm thickness were obtained. The PXRD patterns revealed the presence of two phases. Plate-like kaolinites are found. Also we observed the formation of a halloysite-like phase. Studies of synthesized samples by IR spectroscopy and thermal analysis revealed the presence of organic-modified hydrosilicate with phase transition around 412 degrees C. The resulting phase is promising for studying the processes of adsorption and further exfoliation.

Epitaxial layers of Al x Ga 1-x As 1-y Sb y with an aluminum content x~60% and antimony content y~3% were successfully grown by molecular-beam epitaxy at low temperature. A developed system of AsSb nanoinclusions was formed in the semiconductor matrix by subsequent annealing. The extended transparency window of the obtained metamaterial allows us to document the absorption of light near the interband absorption edge of the Al x Ga 1-x As 1-y Sb y semiconductor matrix. Parameters of the observed extinction band allow us to attribute the optical absorption to the plasmon resonance in the system of AsSb nanoinclusions. Keywords: molecular beam epitaxy, x-ray diffraction analysis, transmission electron microscopy, optical properties, plasmon resonance.

Методом молекулярно-лучевой эпитаксии при низкой температуре с использованием прерываний роста успешно выращены эпитаксиальные слои Al x Ga 1-x As 1-y Sb y с содержанием алюминия x~60% и содержанием сурьмы y~3%. Путем последующего отжига в полупроводниковой матрице сформирована развитая система нановключений AsSb. Увеличенное окно прозрачности полученного метаматериала позволило надежно документировать широкую полосу поглощения света вблизи края межзонного поглощения полупроводниковой матрицы Al x Ga 1-x As 1-y Sb y . Параметры наблюдаемой полосы экстинкции позволяют связать такое поглощение света с плазмонным резонансом в системе нановключений AsSb. Ключевые слова: молекулярно-лучевая эпитаксия, рентгенодифракционный анализ, просвечивающая электронная микроскопия, оптические свойства, плазмонный резонанс.

AlGaAsSb and AlGaAs films as thick as 1 μm with Al content as high as 60% were successfully grown by low-temperature (200 °C) MBE. To overcome the well-known problem of growth disruption due to a high aluminum content and a low growth temperature, we applied intermittent growth with the temperature elevation to smooth out the emerging roughness of the growth front. Post-growth annealing of the obtained material allowed us to form a developed system of As or AsSb nanoinclusions, which occupy 0.3–0.6% of the material volume. While the As nanoinclusions are optically inactive, the AsSb nanoinclusions provide a strong optical absorption near the band edge of the semiconductor matrix due to the Fröhlich plasmon resonance. Owing to the wider bandgap of the grown Al0.6Ga0.4As0.97Sb0.03 compound, we have expanded the spectral range available for studying the Fröhlich plasmon resonance. The grown metamaterial represents an optically active medium of which the formation process is completely compatible with the epitaxial growth technology of semiconductors.

An experimental study aimed at developing the method of the spontaneous synthesis of InGaN/GaN nanowires formed as radial heterostructures by molecular-beam epitaxy is reported. By means of electron microscopy, it is shown that a wedge-shaped crack can be formed at an In content x = 0.4 and 0.04 in the core and shell, respectively. On the basis of the model of internal structural stresses, a formula is proposed to estimate the critical dimensions and composition for the formation of cracks in nanowires. Comparison of the estimates with the experimental morphology data shows good agreement between them.

A new method for growth of Au-catalyzed lateral Ga(In)AsP nanostructures in a quasi-closed volume from a vapor source under semi-equilibrium conditions has been studied. Varied time-temperature conditions and nucleation modes were examined. It was found that lateral nanostructures elongated in the [1 (1) over bar0] direction are formed on a (100) GaAs substrate at about 500 degrees C. Raising the growth temperature is accompanied by a significant change of the morphology of the nanostructures. The modified surface has a random textured structure with predominant pyramidal faceting. Changes in the alloy composition of the nanostructures were studied.

This work presents the results of the growth, structural characterization and magneto-photoluminescence spectroscopy measurements of GaAs/AlGaAs/InP/GaInP 2 quantum well-quantum dot structures. We demonstrate that GaAs/AlGaAs QDs in these structures are formed above InP/GaInP 2 QDs. This allows us to measure the internal magnetic field in the InP/GaInP 2 QD by monitoring the Zeeman splitting of the excitonic transition in the GaAs/AlGaAs QD.

Planar photonic structures, such as gratings and metasurfaces, are routinely used for beam steering, waveguide coupling, and light localization. However, conventional fabrication techniques that involve lithography are demanding in terms of time and cost. Much cheaper and simpler methods for surface patterning and formation of periodic surface structures are enabled by direct laser processing. Here, we demonstrate low-cost rapid fabrication of high-quality phase gratings based on the formation of laser induced periodic surface structures (LIPSS, or ripples) in Ge2Sb2Te5 (GST) thin films. Due to unique phase change properties of GST, the structures demonstrate strong modulation of refractive index with period controlled by the wavelength of laser irradiation. We study the formation of phase change LIPSS in a broad range of excitation wavelengths and observe transition between regimes with different orientations of generated ripples with respect to laser polarization.

GaAs/GaN heterostructures were grown by molecular-beam epitaxy using GaN/supphire (0001) templates. In spite of a ~20% lattice mismatch, epitaxial growth was realized, so that the GaAs films showed good adhesion and their surface had a large mirror-like area. The GaAs films were as thick as 1μm. The surface profile was characterized by atomic-force microscopy, which gave an average roughness of 10 nm for a 5×5 μm scan. Micro-Raman characterization and transmission electron microscopy (TEM) showed that the epitaxial GaAs films had zincblende lattice with (111) orientation, whereas the GaN substrates had wurtzite symmetry. The GaAs/GaN interface was found to be flat and abrupt. A large number of defects have been observed which originated from relaxation of the large lattice mismatch. The defects included misfit dislocations and nanocavities at the interface, as well as dislocations and stacking faults in the bulk of the GaAs film. Sharp interference fringes and characteristic behavior were observed for the ψ and Δ parameters of spectroscopic ellipsometry in the range of 0.75-5.3 eV. Simulation of the optical properties of the GaAs/GaN/sapphire heterostructure indicated a reasonably good optical quality of the layers and interfaces. Photoluminescence (PL) spectra recorded at the temperatures from 17 to 300 K revealed wide and weak radiative bands. Non-radiative processes dominated in recombination of non-equilibrium carriers. The observed PL broadening originated from the band tails that were a result of the high density of charged defects.

Multi-layered nanosized Al2O3/Ge/Si structures manufactured by electron-beam evaporation and annealed at a temperature within the range 700−900◦C are examined using transmission electron microscopy, Raman spectroscopy and X-ray diffraction techniques. The periodic structure with a good layer planarity is confirmed to retain after heat treatment up to 900◦C. At an annealing temperature above 700◦C, nanocrystallites with a bimodal size distribution start to form within initially amorphous Ge layers, the mean size of small crystallites being determined by Ge layer thickness and annealing temperature. An essential loss of Ge from multi-layered structure after 900oC anneal and development of Ge1−x Six solid solution with x up to 0.07 in the nanocrystallites is revealed.

Laser-induced periodic surface structures (LIPSS) can be fabricated in virtually all types of solid materials and show great promise for efficient and scalable production of surface patterns with applications in various fields from photonics to engineering. While the majority of LIPSS manifest as modifications of the surface relief, in special cases, laser impact can also lead to periodic modulation of the material phase state. Here, we report on the fabrication of high-quality periodic structures in the films of phase-change material Ge2Sb2Te5 (GST). Due to considerable contrast of the refractive index of GST in its crystalline and amorphous states, the fabricated structures provide strong spatial modulation of the optical properties, which facilitates their applications. By changing the excitation laser wavelength, we observe the scaling of the grating period as well as transition between formation of different types of LIPSS. We optimize the laser exposure routine to achieve large-scale high-quality phase-change gratings with controllable period and demonstrate their reversible tunability through intermediate amorphization steps. Our results reveal the prospects of fast and rewritable fabrication of high-quality periodic structures for photonics and can serve as a guideline for further development of phase-change material-based optical elements.

Periodic photonic nano- and microstructures are routinely used for light manipulation at the nanoscale. However, their fabrication process is demanding in terms of time, cost and facilities. Here we demonstrate a rapid laser-assisted method for fabrication of gratings in Ge2Sb2Te5 (GST) thin films, based on the formation of laser induced periodic surface structures (LIPSS). LIPSS formation mechanisms dependent on the wavelength of the operating laser, lead to high flexibility of the process, producing gratings with tunable period and orientation with respect to the initial laser polarization. The phase-change properties of GST, on the other hand, allows to fabricate phase gratings with strong modulation of refractive index, which are rewritable in nature.

The spontaneous synthesis of InGaN/GaN nanowires of core-shell heterostructure using molecular beam epitaxy isinvestigated in the work. It is shown by electron microscopy that a wedge-shaped crack can form at In content x=0.4 and 0.04 in the core and shell correspondent. Based on the model of internal structural stresses, a formula is proposed for estimation of the critical size and composition for the formation of cracks in NWs.The estimations and experimental data of morphology agree with each other.