The effect of rapid thermal annealing (RTA) at 950 and 1000 °C for 3 min on the photoluminescence (PL) in multilayered (~50 layers) nanoperiodical (4/3 nm) a-SiOx/SiO2 and a-SiOx/ZrO2 nanostrucutres (MNS) synthesized using vacuum evaporation has been analyzed in comparison with conventional long-term (~1 h) high-temperature annealing (HTA). It has been shown that the use of sequential anneals (RTA + HTA) at 1000 and 1100 °C, respectively, allows increasing the intensity of the PL band of silicon nanocrystals (at ~800 nm) by 2.5 times as compared with conventional heat treatment. Analysis of the PL spectra suggests that RTA triggers the formation of chain and ring non-phase silicon inclusions and/or small-sized Si nanocrystals (~2 nm) which generate radiation near 600 nm at room temperature. Thus, one can conclude that RTA produces elevated concentrations of the abovementioned silicon nuclei which, upon subsequent HTA, serve as growth centers for larger Si nanocrystals (~3–4 nm). It has been found that SiOx/ZrO2 MNS exhibit a similar behavior (qualitative) of PL spectra after RTA. However, the PL intensity in this case is 5–10 times lower, due to the chemical interactions between the materials of the MNS layers with the formation of zirconium silicides and silicates.
The paper studies the effect of nickel ferrite addition and sintering temperature on the density, dielectric and piezoelectric characteristics of barium titanate ceramics. A density jump is detected, when with an increase in the ferrite content the density first increases and then drops sharply. Moreover, if at a sintering temperature of 1200 °C the maximum density (5.38 g/cm3) occurs at a ferrite concentration of 0.05 mol.%, then at a sintering temperature of 1300 °C the maximum density (5.62 g/cm3) shifts to the region of higher ferrite concentrations and is 0.1 mol.%. Thus, it can be stated that at a sintering temperature of 1300 °C the ferrite addition in an amount of 0.1 mol.% acts as a sintering activator. X-ray phase analysis showed that in alloyed barium titanate the tetragonal splitting of lines is expressed more strongly, and the calculated lattice parameters a and c differ significantly from the parameters of pure barium titanate. The addition of 0.1 mol.% ferrite lowers the Curie temperature of the phase transition from the cubic phase to the tetragonal phase from 117 to 108.5 °C. Activation of the sintering process with the addition of ferrite up to ~0.1 mol.% makes it possible to reduce the sintering temperature to 1300 °C and obtain ceramics with high functional characteristics. Relative density is 93%, specific resistance is ~1010 Ohm·m, permittivity is 1500, piezoelectric modulus d31 is 85 pC/N, electromechanical coupling coefficient is 0.37.
Phase transformations during crystallization of the magnetic metal-oxide compound Sr2Fe1.2Mo0.8O6-δ by the solid-phase reactions method from a mixture of simple reagents 2SrCO3 + 0.6Fe2O3 + 0.8MoO3 have been analyzed. By means of differential-thermal and thermogravimetric analyses it was found that the synthesis of strontium ferromolybdate of the Sr2Fe1.2Mo0.8O6-δ composition proceeds through a series of successive-parallel stages. In this way, when considering the dynamics of phase transformations, it has been found that the main accompanying compounds during the crystallization of the solid solution of double perovskite Sr2Fe1.2Mo0.8O6-δ are Fe2O3, SrCO3, SrMoO4 and SrFeO3. When analyzing the phase composition of the batch consisting of a mixture of initial reagents of stoichiometric composition: 2SrCO3 + 0.6Fe2O3 + 0.8MoO3, it was noted that with an increase in temperature, complex compounds SrMoO4, SrFeO3, and then Sr2Fe1.2Mo0.8O6-δ as well, appear almost simultaneously. This circumstance indicates that the compounds SrMoO4 and SrFeO3 are the structure-forming ones for the solid solution of ferromolybdate – strontium. With a subsequent increase in temperature to 1470 K, it was found that the dissolution of SrFeO3 with the formation of double perovskite Sr2Fe1.2Mo0.8O6-δ occurs faster than the dissolution of strontium molybdate SrMoO4. The results of the analysis indicate the difficult nature of the dynamics of solid-phase reactions during the formation of Sr2Fe1.2Mo0.8O6-δ.
Nanostructured copper oxides (CuO, Cu2O) are regarded as promising anode materials for lithium-ion batteries (LIBs) due to owing high theoretical specific capacity and efficient conversion reaction mechanism with lithium under moderate conditions. On investigating the cyclic characteristics of binder-free CuO/Cu2O anodes at 1C current rate, first charge and discharge capacities were observed to be 455.4 and 431.9 mAh/g, respectively, with a Coulombic efficiency of 94.8 %. However, a gradual mitigated capacity was evident as the discharge capacity was decreased to 352.2 mAh/g by the 20th cycle, which can be attributed to solid electrolyte interphase (SEI) layer formation, electrode degradation, or loss of lithium. Beyond 20th cycles, the battery exhibited a more stable cycling regime, with Coulombic efficiency stabilizing ranging around 82–85 %. By the 40th cycle, discharge capacity was further declined to 339 mAh/g, indicating the ongoing degradation mechanisms, however at a much lower rate, such as SEI layer thickening and electrode pulverization. However, despite the initial instability, the system demonstrated enhanced consistency in later cycles, emphasizing the potential of nanostructured copper oxides as efficient LIB anodes. Future efforts should focus on mitigating long-term capacity fading to enhance performance and cycle life.
This paper analyzes properties of the dielectric/AlGaN/GaN system with an ALD Al2O3 film as a dielectric. It was investigated how the current flow process in the system changes due to the deposition of films with different thicknesses; at what bias voltage the electron emission process from the boundary states begins, and how the properties of the barrier layer in the initial heterostructure affect the parameters of the current in the system. It was found that a positive charge forms at the Al2O3/AlGaN interface, the charge magnitude increasing with the film thickness. It was also shown that film deposition affects the charge magnitude in the channel. It was demonstrated that the frequency at which C–V measurements are carried out affects Dit, i.e., the distribution of the electron states at the boundaries of the Al2O3/AlGaN/GaN system. It was shown that the density of the detected donor-like states increases abruptly with an increase in the measurement frequency. It was furthermore demonstrated that a correctly chosen measurement scheme allows one to estimate the potential contribution of the two boundaries, i.e., AlGaN/GaN and Al2О3/AlGaN, in this case, some of the electrons may remain in the channel.
Within the framework of a fast double-crystal synchrotron monochromator based on adaptive X-ray optics elements–ABXO (Adaptive Bending X-ray Optics) prototype developing, the possibility of its use as a fast X-ray shutter was demonstrated. This work proposes two operational modes for the shutter, which differ in the generated X-ray pulses parameters and depend on the ABXOs operating mode. Achievable temporal parameters of the generated X-ray pulses were estimated and the prospects for their application in time-resolved X-ray research methods are considered.
Nanostructured thin films on silicon and glass substrates have been synthesized by high-frequency pulse-periodic action of laser radiation with a wavelength of 1.064 μm. The morphology of La0.5Sr0.5Co0.9Ni0.1O3 thin films investigated using atomic force microscopy showed that films with a developed surface structure have been obtained. Transmission spectra of La0.5Sr0.5Co0.9Ni0.1O3 films were obtained in the visible, near and mid-IR regions. The maximum transmittance of the laser-deposited La0.5Sr0.5Co0.9 Ni0.1O3 film on silicon is observed in the near IR region of the spectrum and reaches the value of 59 % at a wavelength of λ = 1182 nm. Electrophysical characteristics of La0.5Sr0.5Co0.9Ni0.1O3/Si structures were analyzed. When measuring the longitudinal current-voltage characteristic of the La0.5Sr0.5Co0.9 Ni0.1O3/Si structure under the influence of laser radiation with a wavelength from 405 nm to 1064 nm (at a voltage of more than 1.5 V), a photoelectric effect have been observed. The measured capacitance-voltage characteristics of the studied structure have demonstrated the photo-ferroelectric properties.
The effect of substrate temperature and laser wavelength on the laser deposition of CdTe thin films has been studied. CdTe thin films synthesized on glass substrates have been studied using X-ray spectral microanalysis, X-ray diffraction and scanning electron microscopy. It has been shown that the ratio of elements in the CdTe thin films depends on both the substrate temperature and the laser wavelength. Specific features of the crystalline structure, phase composition and structural parameters of the synthesized CdTe films depending on the deposition process conditions (substrate temperature 100–400 °С, laser wavelength 600–1200 nm) have been revealed. Specifically, CdTe thin films deposited using laser radiation of wavelengths of 600 and 1200 nm have a cubic crystalline structure, while CdTe films obtained at a laser wavelength of 1064 nm have either a hexagonal structure or are a mixture of cubic and hexagonal phases, depending on the substrate temperature. At a low substrate temperature (100 °C) the films crystallize to a hexagonal structure, whereas at higher temperatures (200, 300 and 400 °C) the films are a polycrystalline mixture of cubic and hexagonal CdTe phases, growing predominantly along the [111]C direction. It has been shown that CdTe thin films on glass substrates have similar morphologies but different thicknesses, regardless of deposition conditions.
The influence of prolonged ultraviolet (UV) irradiation on the structural and functional properties of graphene deposited on copper, silicon, and poly(butyl methacrylate) (PnBMA) substrates has been investigated. Using Raman spectroscopy, it was shown that UV exposure induces various types of defects, the nature of which is determined by both the substrate type and the number of graphene layers. It was established that for the transferred PnBMA/Gr1 and PnBMA/Gr2 coatings, a significant increase in specific surface resistance is observed after irradiation, with more pronounced degradation of conductivity being characteristic of the PnBMA/Gr2 sample with fewer graphene layers. It is important to note that despite the increase in resistance, its values for all studied "graphene-PnBMA" coatings remained within the antistatic range (104–1012 Ω/sq) throughout the experiment. The incorporation of commercial graphene nanoparticles into the PnBMA matrix (NP-Gr/PBMA) significantly enhances stability: the composite maintained antistatic properties (resistance of 2–3 kΩ/sq) even after 168 h of irradiation. A critical effect of UV exposure is the transition of the coating surfaces from a hydrophobic to a hydrophilic state due to the photo-oxidation of graphene, which was particularly pronounced in the PnBMA/Gr1 sample. The results demonstrate that the stability of graphene-containing coatings under UV irradiation is determined by the number of graphene layers and the properties of the substrate.
The effect of rapid thermal annealing in H2 atmosphere on the ohmic properties of contacts on the basis of two-layered transition metals (e.g. Ti, Ni, Pd and Cr) and Au compositions on р+-Si has been studied. It has been shown for the example of two-layered Ti/Au compositions that rapid thermal annealing in H2 atmosphere at 340 °C for 20 s provides for an ohmic contact with lowest specific resistivity due to the formation of silicides at the Si/Me interface (Me = Ti, Ni, Pd and Cr). The applicability of the process in silicon diode technology for reducing the series resistance and increasing the device yield has been confirmed for small contact area commercial p+–n clamping diodes. Furthermore, the effect of rapid thermal annealing in H2 atmosphere on the level of reverse dark currents in highly ohmic p-Si photodiode has been studied. The results for the commercial p–i–n silicon multi-pad photocells suggest an improvement of the dark currents of the photosensitive pads and the guard ring after rapid thermal annealing in H2 atmosphere at 450 °C for 5 s and an increase in the device yield. This can be attributed to the hydrogen saturation of the dangling silicon bonds, providing for a decrease in the density of the surface states and stabilization of the charge properties at the SiO2/p-Si interface. The applicability of rapid thermal annealing in H2 atmosphere for dark current reduction in highly ohmic p-Si photodiode technology has been confirmed.
Replacement of highly noxious led zirconate titanate based materials in MEMS applications for environmentally safe materials remains an important task. Complex multicomponent doping of KNN ceramics provides for a significant improvement of their ferroelectric properties. The efficiency of different machine learning (ML) methods in the prediction of piezoelectric coefficient of KNN-based ceramics has been analyzed. ML integration allows one to accelerate the development of new materials and identify latent interdependences between their composition, structure, and properties. To understand the mechanisms of relationship between the composition and properties, we used the Sure Independence Screening and Sparsifying Operator (SISSO) method in combination with regression ML methods, such as Support Vector Regression, Ridge, Lasso, Elastic Net, Xtreme Gradient Boosting, Random Forest, Gradient Boosting Regression, and Extreme Tree Regression. The Gradient Boosting Regression (GBR) method proved to be the most efficient in combination with SISSO. The test sampling accuracy reached 81 %, and GBR validation for experimental data delivered a mean absolute error of 26 pC/N.
The article describes the preparing process for composites with a polyimide varnish PILK-2B matrix, which filled with particles of technical diamond, copper oxide, cubic boron nitride and hexagonal boron nitride for use in redistribution layers during chip packaging. Article show the results of the adhesive properties study for these composites with various fillers in relation to alkali glass and ST50 sitall substrates using the pull-off method. The measurement showed that the maximum adhesion to sitall and glass substrates is characteristic of the composite based on cubic boron nitride. It is 20.97 MPa and 20.11 MPa, respectively. Composites based on technical diamond and hexagonal boron nitride show lower adhesion – 17.48 and 18.03 MPa for sitall, 17.27 and 16.84 for glass. The material based on copper oxide show a significant difference in adhesion for sitall and glass – 14.78 MPa and 19.65 MPa, respectively. In addition, the article presents the results of composite processing using infrared nanosecond laser ablation to obtain structures in the form of traces and cylinders (contact pads) of various sizes. Cubic boron nitride based composites show clearest pattern with minimum line/space parameter of 25 µm and minimum delamination. Composite based on hexagonal boron nitride show the worst result with the maximum number of damages and flakes during laser treatment.
Based on previously proposed approaches for implementing monochromatic X-ray beam rapid spectra modulation method using adaptive X-ray optical elements, a new spatially resolved technique has been developed. This technique was applied to record the tantalum L3 edge absorption spectra linear distribution with 37 µm spatial resolution. This method accelerates the sample's structure study rate by increasing the illuminated area compared to the classical X-ray absorption spectroscopy method and increasing the volume of information obtained relative to X-ray fluorescence. This approach is promising for studying crystalline materials with complex structure used in the microelectronics industry.
This work is devoted to the development of an electrode material for energy storage devices and its nanostructuring technology, which significantly improve energy characteristics. The electrode material consists of a conductive carbon flexible matrix with a high specific surface area filled with silver nanoparticles measuring 10–40 nm. The design and manufacturing technology of a supercapacitor based on an aqueous electrolyte with an operating voltage of 2.6 V and a specific energy consumption of 5.5 Wh/kg are presented.
Herein, we report a systematic investigation of the synthesis methodology, structural characteristics, and electrochemical performance of CoMn/C metal-carbon nanocomposites derived via IR pyrolysis from manganese-substituted metal-organic frameworks (MOFs) exhibiting ZIF-67 topology. The MOF precursors were synthesized utilizing a chemical co-precipitation approach in aqueous media under ultrasonic treatment, with systematic variation of Co:Mn molar ratios ranging from 95:5 to 50:50, employing 2-methylimidazole as the organic linking agent. X-ray diffraction analysis coupled with electron microscopy investigations revealed that manganese incorporation into the cobalt sites is feasible up to a Co:Mn ratio of 70:30 while maintaining the intrinsic ZIF-67 crystalline architecture, concomitantly leading to a systematic reduction in crystallite dimensions from 36 to 21 nm and corresponding morphological modifications. The subsequent IR pyrolysis conducted within the temperature range of 500–700 °C yielded metal-carbon nanocomposites comprising homogeneously dispersed Co, MnO2, and Mn3O4 nanoparticles within a porous carbonaceous matrix. Electrochemical characterization demonstrated optimal specific capacitance values of 336 F/g at 0.25 A/g current density for nanocomposites exhibiting Co:Mn ratio of 80:20, synthesized at the optimal pyrolysis temperature of 600 °C. The resultant materials exhibited exceptional cycling stability, maintaining capacitance retention exceeding 95 % through 1000 charge-discharge cycles, while demonstrating robust performance across a broad potential window up to 1.4 V in 6M KOH aqueous electrolyte. The enhanced specific capacitance values are attributed to the synergistic contribution of double-layer capacitance from the developed porous carbon framework and pseudocapacitive effects arising from reversible redox processes of metallic nanoparticles and their corresponding oxides. These findings elucidate the significant potential of Mn-substituted MOFs as precursors for the fabrication of high-performance electrode materials in symmetric supercapacitor applications, exhibiting superior electrochemical characteristics.
The development of nanotechnology requires more advanced computer modeling methods to study the properties of nanoparticles and clusters. These particles are the main “building material” in nanotechnology, determining the unique properties of the created products. Computer modeling makes it possible to predict the behavior of nanoparticles, their interaction with the environment and with each other, as well as optimize the processes of their synthesis and application. Due to their lightness and flexibility, conductive polymers open up new possibilities for the development of flexible and wearable electronics. Currently, research is quite widespread on the creation of new polymer materials, which are obtained by modifying known polymers with various fillers, including nanomaterials. One of the well-known nanomaterials is carbon nanotubes. The existing applications of nanotubes are almost limitless. In this work, the well-known polymer polyvinyl alcohol and carbon nanotubes are chosen as the main objects. A theoretical study of the possibility of creating a stable Polymer-CNT complex using the quantum chemical calculation method DFT has been performed. Single- and double-walled carbon nanotubes were used in the study. The mechanism of interaction of nanotubes with fragments of polyvinyl alcohol has been studied. The electron-energy structure of the obtained polymer nanocomposites is analyzed and a conclusion is made about the conductive properties of the resulting complex.
In this paper, we have investigated piezoelectric, magnetic and magnetoelectric properties of composite materials, consisting of polyvinylidene fluoride (PVDF) matrix and CoFe2O4 nanoparticles in the form of filament extrusion and 3D printed films. We used PVDF powders from different manufacturers each with different molecular weights and phase compositions. For PVDF with lower molecular weight and higher electroactive phase content of the, we observed that approximately 80 % of the electroactive phase in the starting polymer was effectively transferred to the printed films through all technological stages. The composite filaments exhibited ferromagnetic behavior with a large coercive force of 1.7±0.1 kOe consistent with a particle size of about 20 nm. The magnetoelectric coefficient was about 2 mV/(Oe∙cm) for printed composite films from both precursors, which is sufficient for a range of applications including microelectronics and tissue engineering using magnetically stimulated electric fields.
This study presents a comparative performance analysis of GaAs, InP, and GaN-based MOSFETs using Spreading Resistance Profiling (SRP), Capacitance–Voltage (C–V) simulation, and Finite Element Analysis (FEA) within a sentaurus technology computer-aided design (TCAD) environment. The results show that GaN MOSFETs achieve the highest on-current (450 µA) and peak gm (400 µS), but exhibit a slightly higher ON-resistance (5 Ω) compared to GaAs (4.44 Ω) and InP (4.21 Ω). In terms of VTH uniformity, GaN demonstrates superior dopant stability with the lowest standard deviation (0.143 V), followed by InP (0.213 V) and GaAs (0.266 V). These findings highlight the trade-offs between current drive, resistance, and variability among III–V materials, with GaN offering strong performance and reliability characteristics suitable for secure and thermally stable semiconductor applications.
In the current investigation, we have implemented first-principles calculations to examine the structural, elastic, electrical and optical characteristics of Cs 2 AB H 6 (AB = AlGa, AlIn, AlTl, NaAl, NaGa, NaIn and TlIn). All of the calculations were performed out using first-principles density functional theory (DFT). The space group Fm -3 m (225) has been used. The computed values of lattice parameters are Cs 2 AlGaH 6 : 0.8739 nm, Cs 2 AlInH 6 : 0.8923 nm, Cs 2 AlTlH 6 : 0.8953 nm, Cs 2 NaAlH 6 : 0.8669 nm, Cs 2 NaGaH 6 : 0.8688 nm, Cs 2 NaInH 6 : 0.8960 nm, Cs 2 TlGaH 6 : 0.8938 nm and Cs 2 TlInH 6 : 0.9258 nm and also it is observed that the volume and density are inversely associated with each other. In addition, the computed band-gap values for Cs 2 AlInH 6 , Cs 2 AlTlH 6 , Cs 2 NaAlH 6 , Cs 2 NaGaH 6 , Cs 2 NaInH 6 , Cs 2 TlGaH 6 and Cs 2 TlInH 6 and Cs 2 YAuCl 6 are 1.21, 1.66, 2.58, 1.32, 1.42, 0.94 and 0.91 eV, respectively, which demonstrates the indirect semiconducting nature. Between 0 and 20 eV, optical spectra calculations are made, taking into account the real and imaginary parts of the dielectric function e(?), reflectivity R (?), index of refraction n (?), coefficients of extinction k (?) and absorption a(?). The dielectric function is wide close to the ultraviolet districts (3.10–4.13 eV). The extinction coefficient of the Cs 2 AB H 6 has the ability to worn for implements like Bragg’s reflectors, optical and optoelectronic equipments. The optical parameters of Cs 2 AB H 6 disclose that our working constructions have an elevated dielectric constant, with a greatest absorption in the visible range holding out over 2.45·10 5 cm -1 . All three compounds fulfil the Born stability condition. The gravimetric hydrogen storage capacities of Cs 2 AlInH 6 , Cs 2 AlTlH 6 , Cs 2 NaAlH 6 , Cs 2 NaGaH 6 , Cs 2 NaInH 6 , Cs 2 TlGaH 6 and Cs 2 TlInH 6 compounds are 1.64, 1.20, 1.88, 1.66, 1.48, 1.02, 1.11 and 1.20 wt.%, respectively. Cs 2 ABH 6 crystals are dynamically stable.
This study presents the synthesis of LiMn 0.9 Fe 0.1 PO 4 (LM9F) and its carbon-coated counterpart, LiMn 0.9 Fe 0.1 PO 4 with 10% carbon (LM9F-10%C), through a straightforward solid-state method. The synthesis utilized lithium carbonate, manganese (II) acetate tetrahydrate, iron phosphate, ammonium dihydrogen phosphate, and glucose powder as the carbon source. To achieve a fine powder, a high-energy ball milling was performed at 270 rpm for 8 h, followed by calcination at 700 °C for 3 h and sintering at the same temperature for an additional 2 h, under a nitrogen atmosphere to prevent iron oxidation. Thermoanalytical techniques (TGA–DTA–DSC) were applied between 30 °C and 1000 °C to study the thermal decomposition behaviors of the precursors and pinpoint the phase formation temperature, which was identified at 416 °C. X-ray diffraction analysis verified the formation of a pure olivine orthorhombic structure, corroborated by Rietveld refinement. The morphology of the calcined powders, characterized by field emission scanning electron microscopy, showed agglomerated semi-spherical particles with an average size of 34 nm. Fourier transform infrared spectroscopy confirmed the presence of the phosphate groups integral to the olivine framework. Electrical properties measured via an LCR meter across 20 Hz to 100 kHz demonstrated that the inclusion of carbon significantly reduced impedance and improved the electrical performance of the materials.
