East European Journal of Physics

Exploring Bianchi Type III Universe with Quadratic Trace of Stress-Energy Tensor in f(R, T) Theory of Gravity

Chandra Rekha Mahanta — 2026-06-10

In this work, we consider a spatially homogeneous and anisotropic Bianchi type III universe in f(R, T) gravity with the functional form f(R, T) = f₁(R) + f₂(T) with f₁(R) = λ₁R and f₂(T) = λ₂T + λ₃T², where λ₁, λ₂ and λ₃ are free parameters. We obtain exact solutions of the gravitational field equations by considering a power-law expansion of a directional scale factor. By keeping a check on the current values of the parameters of cosmological significance such as the Hubble parameter H and the deceleration parameter q, the dynamics and physical characteristics of the model are investigated. We also determine the functional form f(R, T) of our model by evaluating the Ricci scalar R and the trace T of the stress-energy tensor. We find that our model remains anisotropic throughout its evolution and the pressure of the cosmic matter remains negative. The equation of state parameter ω is found to lie in the quintessence regime and therefore our model behaves like quintessence model of dark energy.

Constraining Kaniadakis Holographic Dark Energy Model in Bianchi Type–III Cosmology

Y. Aditya — 2026-06-10

In this work, we study the cosmological dynamics of an anisotropic Bianchi type--III universe filled with Kaniadakis holographic dark energy and pressureless matter within the framework of Brans--Dicke--Rastall theory of gravity. To obtain exact solutions of the field equations, suitable relations among the metric potentials are assumed, together with a functional relation between the scalar field and the average scale factor. To constrain the model parameters, we perform a Markov Chain Monte Carlo analysis using joint CC+BAO datasets. The reconstructed Hubble parameter shows excellent agreement with observational data within the 1σ and 2σ confidence regions, and the estimated value of the Hubble constant is consistent with recent measurements. We derive several important cosmological parameters, including the Hubble parameter, deceleration parameter, equation of state parameter, scalar field, cosmic time and lookback time. The physical behavior of these parameters is analyzed through graphical representations. The deceleration parameter exhibits a smooth transition from an early decelerated phase to a late--time accelerated phase, with a transition redshift consistent with recent observational bounds. The equation of state parameter remains in the phantom region, indicating a dynamical dark energy behavior capable of driving the current accelerated expansion. Furthermore, the statefinder (r,s) and (r,q) diagnostics reveal that the model closely approaches the ΛCDM behavior at late times, while allowing deviations at earlier epochs. The Οm(z) diagnostic further supports the phantom--like nature of dark energy in the present framework. Overall, our results demonstrate that our model in Brans--Dicke--Rastall gravity provides a viable and observationally consistent description of the cosmic expansion history in an anisotropic universe.

Axially Symmetric Cosmological Model in f(Q,T) Gravity

M.T. Sarode — 2026-06-10

This article is devoted to the study of the dynamical aspects of the domain wall cosmological model in an axially symmetric space-time in f(Q,T) gravity. In this theory of gravity, the action contains an arbitrary function f(Q,T) where Q and T respectively denote the non-metricity and the trace of energy momentum tensor. The linear and additive form of f(Q,T) gravity, f(Q,T) = μQ + νT where μ and ν are non-zero arbitrary constants, is taken into account in this work. A deterministic model of the universe is obtained using the linearly varying deceleration parameter q = -kt+m-1 which is linear in time with negative slope. We have assessed all the dynamical and geometrical parameters of the models and examined their physical significance in modern cosmology. We have observed that the deceleration parameter displays a signature-flipping point where shifting occurs from a decelerating regime to an accelerating regime, signifying cosmic expansion. It is observed that our model is in good agreement with the current scenario of accelerated expansion of the universe.

Bianchi Type–VII Cosmological Model with Tsallis–Barrow Holographic Dark Energy in Lyra Geometry

R. Santhi Kumar — 2026-06-10

In this work, we investigate an anisotropic Bianchi type–VII cosmological model in the framework of Lyra geometry filled with perfect fluid matter and Tsallis–Barrow holographic dark energy. The modified Einstein field equations are derived, and exact solutions are obtained by assuming a power-law average scale factor for a decelerating universe. Expressions for various cosmological parameters such as the Hubble parameter, expansion scalar, shear scalar, matter density, dark energy density, and density parameters are derived and analysed. The behaviour of these parameters indicates that the universe is expanding continuously, with the expansion rate decreasing with cosmic time. The anisotropy parameter decreases gradually, indicating that the universe evolves towards isotropy at late times. Energy conditions, stability analysis, and cosmological diagnostics, including the statefinder and Om parameters, are also examined to evaluate the model's physical viability. The results suggest that Tsallis–Barrow entropy corrections in Lyra geometry provide a consistent framework for studying anisotropic cosmological evolution and dark energy dynamics.

Magnetized Anisotropic Dark Energy Cosmological Model in f(T) Gravity with a Special Law of the Hubble Parameter

K.N. Pawar — 2026-06-10

In this paper, we investigate a magnetized anisotropic dark energy cosmological model in the framework of f(T) gravity for a locally rotationally symmetric Bianchi type-I spacetime. Choosing f(T)=0 reduces the theory to teleparallel gravity, dynamically equivalent to general relativity, enabling direct comparison with standard cosmology. Exact solutions of the field equations are obtained by assuming a special law of the Hubble parameter with a nonzero constant S, yielding power-law behavior of the directional scale factors.
A uniform magnetic field aligned along one spatial direction produces an early-time anisotropy whose energy density decays with cosmic expansion. The energy density, pressure, the equation-of-state parameter, and the energy conditions are analyzed. The pressure remains negative, while the equation-of-state parameter evolves dynamically and approaches the range -1 ≤ ω < -1/3 at late times, consistent with SN Ia and CMB constraints. The null and weak energy conditions are violated at late times, whereas the strong energy
condition is violated throughout, implying acceleration.

A Pen-Picture of the Modified (2+1)-Dimensional KdV-Calogero Bogoyavlenskii-Schiff Equation in Shallow Water Waves: Lie Symmetry Analysis and Conservation Laws

Sivenathi O. Mbusi — 2026-06-10

This work investigates the KdV-Calogero Bogoyavlenkskii-Schiff equation in modified (2+1) dimensions. The Lie symmetries are created using Lie group analysis, and the similarity solutions are then found using the symmetries. Using the multiple exp-function approach, numerous wave solutions are obtained. Furthermore, we use the multiplier approach to express the conserved currents, which is essential for comprehending the nature of non-linear equations, particularly in engineering and physics.

Effects of Non-Thermal Electrons and Non-Extensive Positrons on Solitary Waves in a Multi-Component Dusty Plasma

Satyendra Nath Barman — 2026-06-10

In this study, we have investigated the existence and characteristics of solitons in an unmagnetized dusty plasma composed of cold ions, negatively charged dust grains , positively charged dust grains, non-thermal electrons and non-extensive positrons. The properties of solitons are usually studied through the Reductive Perturbation method and the Sagdeev Potential method. We have derived the energy integral equation using the Sagdeev Potential method. We have also discussed the variation of the Sagdeev potential for different values of the parameters involved in our plasma model. The non-extensive parameter (q), the non-thermal parameter (β), charge density ratio of positively charged dust (δ₊) , charge density ratio of negatively charged dust (δ_{_}), positron to ion density ratio (δ_p), electron to ion density ratio (δ_e), electron to positron temperature ratio (σ_p) and the Mach number (M) found to influence the amplitude of solitons. Our study reveals that non-thermality of electrons and non-extensivity of positrons significantly modify the soliton features. The results from our study can be useful for investigating plasma in space environments such as cometary tails and interstellar clouds.

Doppler Spectra for Stationary and Dynamic Ultrasonic Fields

Mykhailo O. Hrytsenko — 2026-06-10

This paper presents a review of physical and methodological approaches to describing the spectrum of the ultrasonic Doppler signal in biological media. The results on the formation of spectral characteristics for a stationary probing field under different types of scatterer motion are summarized, and the development of the model for the case of a dynamically varying sensitivity function of the ultrasound system is considered. Particular attention is paid to synthetic aperture, dynamic focusing, and coherent plane-wave compounding
modes. It is shown that in plane-wave imaging systems the Doppler signal spectrum is determined not only by the motion properties of the medium, but also by the spatiotemporal method used to form the Doppler response. The results concerning spatial resolution in the plane-wave compounding mode are also summarized, and the relationship between the geometry of the measurement volume, the sensitivity function, and the spectral parameters is analyzed. Prospects for the further development of these approaches, in particular for applications in shear-wave elastography, are outlined.

Neutron and Gamma-Ray Pulse Shape Discrimination Methodology

I. Yakymenko — 2026-06-10

In this research, we proposed a new neutron gamma discrimination methodology in comparison with the classical charge integration. To record an experimental dataset, a high sampling rate oscilloscope, Keysight DSOX 6004a (20 Gas/s), was used. The reference experiment was recorded with the desktop digitizer CAEN DT 5720e with DPP PSD firmware installed. A stilbene scintillator size of 50 mm x 50 mm coupled with the PMT R1307 Hamamatsu was selected as a detector. The scintillation pulse decay has an exponential tail depending on the particle nature. The proposed technique aims to classify the geometrical peak asymmetry of the scintillation pulse detected by the detector, where the discrimination factor is a ratio of the calculated pulse weight (centroid) related to the pulse maximum amplitude position in time. The centroid of the faster gamma pulse is closer to the pulse maximum amplitude and significantly shifted for the delayed neutron pulses. The discussed approach allows us to classify events with comparable accuracy to the charge integration technique.

Porous Ceramics and Metal Hydride Materials for Efficient Hydrogen Storage

M.S. Payzullakhanov — 2026-06-10

In this work, we investigated synthesized porous aluminosilicate materials containing burnable additives, which form a single-phase cubic zeolite structure (Fm3m, a=4.056 Å). The porous ceramic with a zeolite composition at 200°C and a hydrogen pressure of 12 atm exhibited hydrogen absorption of 11 wt.%. We also studied the initial metallic lithium (BCC, a ≈ 3.507 Å), which was subjected to hydrogenation in the developed sealed reactor at 12 atm and 700 °C with the formation of LiH hydride (FCC, NaCl type, a ≈ 4.081 Å, d₁₁₁ ≈ 2.356 Å). The average size of LiH crystallites does not exceed 100 nm, and the maximum hydrogen capacity of lithium reached 12.4 wt.%. The developed reactor enables safe, high-temperature, high-pressure hydrogenation. These data demonstrate the potential of lithium, titanium, and sodium hydrides, and porous aluminosilicates for the accumulation, storage, and transportation of hydrogen.

Substitutional Tb Incorporation, p–n Conductivity Transition, and Gamma-Irradiation Effects on the Thermoelectric Properties TbₓSn₁₋ₓSe Solid Solutions

T.A. Jafarov — 2026-06-10

The physicochemical and thermoelectric properties of TbₓSn₁₋ₓSe (0 ≤ x ≤ 0.05) solid solutions were systematically investigated with emphasis on composition-driven carrier-type transition and γ-irradiation effects. Differential thermal analysis reveals a monotonic decrease in melting temperature and enthalpy with increasing Tb content, indicating lattice distortion and reduced thermal stability due to the substitutional incorporation of Tb³⁺ at Sn²⁺ sites. X-ray diffraction confirms single-phase orthorhombic (Pnma) structure without secondary phases, while EDX analysis verifies successful Tb incorporation. A composition-induced p-n transition occurs within a narrow concentration range, accompanied by a significant modification of the Seebeck coefficient. γ-irradiation (up to 4-6.5 Mrad) significantly affects the Seebeck coefficient in the low-temperature region (80-300 K), with a nonlinear dose dependence that can be approximated by a quadratic function. At elevated temperatures (T ≥ 500 K), the thermoelectric response exhibits notable radiation stability. The obtained results clearly indicate that Tb doping facilitates a controllable modulation of charge carrier transport properties while preserving the structural integrity and thermal stability of the material at elevated temperatures. These findings underscore the strong potential of Tb-doped systems for advanced thermoelectric applications, particularly under radiation-exposed operating conditions.

Mg-Induced Enhancement of Memristive Switching in SnO₂ Thin Films

Jamoliddin X. Murodov — 2026-06-10

Magnesium-doped tin oxide (SnO₂:Mg) thin films have attracted considerable attention as promising materials for next-generation non-volatile memory devices due to their stable resistive switching behavior and simple fabrication processes. In this work, SnO₂ thin films were fabricated by ultrasonic spray pyrolysis using a precursor solution containing 20 mol.% Mg and systematically investigated to evaluate their memristive switching characteristics, electrical performance, and conduction behavior. Structural analysis confirmed the formation of uniform polycrystalline thin films with a crystallite size of approximately 30 nm, while energy-dispersive X-ray spectroscopy (EDS) revealed an actual Mg content of approximately 5 at.%, indicating partial incorporation of Mg into the SnO₂ lattice. Electrical measurements demonstrated reproducible bipolar resistive switching with an ON/OFF resistance ratio of approximately 10³ and stable switching behavior over multiple cycles with low voltage variation (±5%) compared to previously reported undoped SnO₂ films. The observed improvement in memristive performance is attributed to Mg-induced modifications of defect states and charge-transport pathways within the oxide matrix. Conduction analysis indicates a transition from ohmic behavior at low bias to space-charge-limited conduction (SCLC) at higher voltages, consistent with a quadratic current–voltage relationship (I ∝ V²). These results demonstrate that Mg incorporation is an effective defect-engineering strategy for tuning the electrical properties of SnO₂ thin films and improving their suitability for reliable memristor and non-volatile memory applications. This approach provides a simple and scalable route for engineering oxide-based memristive devices.

Impact of Direct and Pulsed Electrodeposition Mode on the Electrochemical, Structural, and Morphological Properties of Ni-Fe Nanostructures Coatings

Houssem Eddine El Yamine Sakhraoui — 2026-06-10

Nickel-iron (Ni-Fe) nanostructured alloys are attracting increasing interest due to their remarkable electrochemical, magnetic, and mechanical properties, making them particularly attractive for applications in electrocatalysis, energy storage, sensors, and functional coatings. This study presents a comparative analysis of the electrochemical, structural, and morphological characteristics of nickel-iron (Ni-Fe) nanostructures synthesized in sulfate electrolytes on indium tin oxide (ITO) substrates through various electrodeposition methods. The fabricated nanostructures were characterized using cyclic voltammetry, chronoamperometric measurements (potentiostatic steps), atomic force microscopy (AFM), and X-ray diffraction (XRD). The electro-crystallization process was evaluated using the Scharifker-Hills model, revealing that nucleation mechanisms differed based on applied potentials. XRD analysis confirmed the polycrystalline nature of the Ni-Fe nanostructures, with a preferred <111> crystallographic orientation and a face-centered cubic (fcc) structure observed in both deposition modes. The crystallite sizes were determined as 9.77 nm under pulsed conditions and 14.63 nm for the direct method. AFM surface analyses further demonstrated that the choice of electrodeposition method significantly influences the morphological features of the resulting deposits.

Self-Consistent Fowler–Nordheim Tunneling Modeling in Si/GaAs Heterostructures with Optimized Nanoscale Meshing

Jo‘shqin Sh. Abdullayev — 2026-06-10

The Fowler–Nordheim (FN) tunneling current in GaAs was systematically analyzed as a function of electric field (25–50 MV/cm) and temperature (250–400 K) to evaluate its potential for high-sensitivity structural temperature sensing. Two physical descriptions were considered: a constant electron effective mass model and a field-dependent effective mass formulation. For the constant-mass approximation, the FN tunneling threshold appears at approximately 25.2 MV/cm, where the current rises rapidly from ~10⁻¹² to 10⁻⁶ A/cm² with increasing electric field. When field-dependent effective mass effects are incorporated, the threshold shifts to ~28.6 MV/cm and intermediate-field currents are suppressed by nearly one order of magnitude. Temperature variation increases the FN prefactor by approximately 30–35%, indicating measurable thermal sensitivity, although the exponential dependence on electric field remains the dominant factor controlling tunneling transport. These characteristics demonstrate the feasibility of exploiting FN tunneling mechanisms for nanoscale temperature sensing in high-field semiconductor structures. In addition, a self-consistent FN tunneling framework was developed for a p-Si/n-GaAs heterostructure to evaluate numerical stability and predictive accuracy for temperature-dependent tunneling simulations. Two tunneling formulations were compared: a conventional simplified FN model and an effective-mass-corrected model. A comprehensive mesh convergence analysis using rectangular and triangular discretizations with spatial resolutions from 0.5 to 20 nm shows that coarse meshes can introduce errors up to 12%, whereas sub-nanometer meshing ensures convergence below 1%. The effective-mass-corrected model consistently predicts 5–15% higher tunneling currents across the 0.5–3.0 V bias range, highlighting the importance of band-structure corrections for reliable sensor modeling. Furthermore, adaptive triangular meshes achieve comparable accuracy with up to 40% fewer elements, significantly improving computational efficiency. These results establish a robust numerical framework for simulating FN-based tunneling transport in semiconductor heterostructures and provide practical guidelines for mesh optimization in advanced TCAD studies. The proposed methodology supports the development of compact, high-sensitivity FN-based temperature sensors suitable for integration into nanoscale electronic, optoelectronic, and structural monitoring systems.

The Systematic Correlation Between Synthesis Parameters and the Particle Size of Nickel Oxide Nanocatalysts Prepared by the Sol–Gel Method

Ilyos J. Abdisaidov — 2026-06-10

In this work, the sol-gel synthesis of nickel oxide (NiO) nanoparticles was systematically examined with respect to key parameters, including precursor type, reagent molar ratio, reaction time, and calcination temperature. A comparative evaluation of different nickel-based salts identified nickel nitrate as the most suitable precursor. Structural–phase characterization by X-ray diffraction (XRD) demonstrated that the nanoparticles synthesized at varying reagent ratios possessed well-defined crystalline phases, with an average crystallite size of ~11 nm. Prolonged reaction times were observed to promote agglomeration processes. Raman spectroscopic analysis revealed the presence of phonon and magnon vibrational modes, which were strongly dependent on particle size and calcination conditions. Transmission electron microscopy (TEM) confirmed a particle size distribution in the range of 3÷19 nm. Collectively, these results establish the synthesis–structure relationship and provide a framework for defining optimal conditions for preparing NiO nanocatalysts.

Optical and Magneto-Optical Properties of Na₀.₃₇₅Tb₀.₆₂₅F₂.₂₅ Crystal

M.E. Malysheva — 2026-06-10

Optical and magneto-optical spectra of the Na_0.375Tb_0.625F_2.25crystal have been studied within the ultraviolet and visible spectral range. It has been established that within the wavelength range of 535-560 nm there is an intense luminescence band caused by intra-configurational 4f→4f transitions ⁵D₄→⁷F₅. In the luminescence band ⁵D₄→⁷F₅and ⁵D₄→⁷F₄the radiative 4f→4f transitions have been identified and it has been established that the magnetic dipole transitions dominate in the secondary emission spectra. Analysis of magneto-optical research data has demonstrated that the C-term of magneto-optical activity plays a significant role in the mechanism of occurrence of magneto-optical effects on luminescence bands caused by “forbidden” 4f→4f transitions. A comparative analysis of the dispersion dependence of the Verdet constant of the Na_0.375Tb_0.625F_2.25single crystal showed that it is about 90% of the Verdet constant of the well known Tb₃Ga₅O₁₂ crystal, which demonstrates a good magneto-optical properties of the new synthesized crystal.

DFT Investigation of Electronic, Elastic, and Transport Properties, and Evaluation of Lattice Thermal Conductivity of the Half Heusler Alloy RuAsNb

Aziza Boutouta — 2026-06-10

In this study, we employed the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method, as implemented in Wien2k, to perform a comprehensive investigation of the structural, electronic, and thermoelectric properties of RuAsNb. The electronic band structure was calculated using the TB-mBJ exchange-correlation potential, resulting in an energy gap that is in close agreement with the available experimental data. Furthermore, our analysis revealed favorable optical properties, highlighting the material’s potential for applications across the infrared, visible, and ultraviolet regions of the electromagnetic spectrum. We also evaluated the thermoelectric performance of RuAsNb by analyzing key parameters, including the Seebeck coefficient, electrical conductivity, thermal conductivity, and power factor. The results indicate that holes are the dominant charge carriers, confirming the p-type semiconducting nature of RuAsNb. In addition, the effect of chemical potential variations on these thermoelectric properties was examined, providing valuable insights into their temperature-dependent behavior. To ensure the robustness of our findings, a comparative study using different exchange–correlation potentials was conducted, which further validated the consistency of the results. The promising thermoelectric performance of RuAsNb suggests its suitability as a potential candidate for next-generation energy conversion devices and photovoltaic applications. Moreover, the estimation of the lattice thermal conductivity using the Slack model reinforces the reliability of our predictions and provides valuable insights for future research. Overall, this work contributes to a deeper understanding of the potential of RuAsNb in advanced energy materials.

Investigation of the Microstructure of Photosensitive CdSe and CdSe:Cd,Cl Thin Films

Iftixorjon I. Yulchiyev — 2026-06-10

The substructure of freshly prepared photosensitive CdSe and doped CdSe:Cd, Cl thin films was investigated with respect to the influence of substrate temperature T_s and heat-treatment time in air in the presence of vapor. The results of electron diffraction and electron microscopy studies for films prepared under different technological conditions are also presented. It was established that the texture axis of the as-prepared CdSe films is perpendicular to the substrate plane. As T_s increases from 250 to 400°C, the texture-axis dispersion angle, the fraction of the hexagonal phase, the crystallite size, and the coherent X-ray scattering region size increase. After annealing in air in the presence of CdCl₂ vapor at 300°C, films prepared at T_s=250°C exhibit reorientation of crystallites from the (111)_c+(0002)_h plane, which is parallel to the substrate plane, to the (10¯1 3) orientation through the (311)_c+(11¯1 2)_h planes. This reorientation is accompanied by an increase in crystallite size and D_csr, and by a decrease in the lattice parameter and the minimum dislocation density.

The Effect of Temperature on the Energetic Position of the Fermi Level in Porous Silicon

U.S. Babakhodzhaev — 2026-06-10

This paper presents the theoretical investigation of the temperature-dependent shift of the Fermi level in porous silicon (por-Si). The study is based on the charge-state distribution model originally proposed for hydrogenated amorphous silicon (a-Si:H), with consideration of the unique physical and chemical properties of porous silicon (por-Si). The temperature dependence of the parameters in the charge-state density within the bandgap is accounted for in both simplified and advanced models. For each model, the Fermi-level shift behavior was calculated using numerical methods based on integral-differential equations. The results are presented in graphical form, and the physical mechanisms underlying the Fermi level shift across different temperature ranges are discussed. The conclusions obtained can be applied to explain carrier transport processes, reduce surface recombination, and improve the efficiency of por-Si/c-Si heterostructure-based solar cells.

Experimental and Simulation-Based Study on the Structural, Optical, and Mechanical Properties of PLA/ZnO Nanocomposites

Fakhriddin T. Yusupov — 2026-06-10

This work presents a comprehensive experimental and theoretical investigation of polylactide (PLA) nanocomposites reinforced with zinc oxide (ZnO) nanoparticles at concentrations of 0.5, 1, 3, and 5 wt.%. The dispersion state and microstructural features of ZnO within the PLA matrix were examined using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, revealing homogeneous distribution at low filler contents and progressive agglomeration at higher loadings. X-ray diffraction analysis confirms that ZnO preserves its hexagonal wurtzite crystal structure after incorporation into the polymer matrix, while composition-dependent variations in crystallite size and lattice microstrain are found to correlate with the mechanical response of the composites. Fourier-transform infrared spectroscopy indicates interfacial interactions between PLA chains and ZnO nanoparticles, as evidenced by systematic shifts in the carbonyl stretching band and associated charge redistribution. Ultraviolet–visible spectroscopy demonstrates a significant enhancement of UV-shielding performance with increasing ZnO content, accompanied by the emergence of sub-bandgap absorption tails attributed to defect-related and interfacial electronic states. Density functional theory calculations support the experimental observations by revealing interfacial charge transfer and a slight modification of the electronic structure at the PLA/ZnO interface. The results show that ZnO incorporation improves both mechanical stiffness and UV-blocking efficiency, while an optimal ZnO loading below 1 wt.% is identified to maintain mechanical integrity and minimize agglomeration-induced degradation.

Critical Size and Doping Thresholds Governing Band Gap Evolution in Semiconductors

J.Sh. Abdullayev — 2026-06-10

Understanding how the band gap ( E_g) of semiconductors evolves with size, dimensionality, and doping concentration is crucial for optimizing modern electronic and optoelectronic devices. In this work, we perform a systematic analysis of critical sizes ( L_c) and doping thresholds (N_c ) governing significant band gap modification in Si, GaAs, InP, CdS, and GaN. Using effective mass theory with Coulomb corrections, Varshni temperature dependence, and numercical simulations, we identify that quantum confinement dominates when L ≲ 2a*_B, yielding L_c= 10 nm for Si, 22 nm for GaAs, 6 nm for CdS, and 5–6 nm for GaN. The corresponding Mott-like critical doping thresholds satisfy N_c^1⁄3 a*_B≈0.25, giving N_c = 1.8·10¹⁸ cm^-3 (Si), 5.6·10¹⁷ cm^-3(GaAs), and 2.9·10¹⁸cm^-3(CdS). For quantum dots (0D) at r = 2nm, band gaps increase by ~0.9 eV for Si, ~1.3 eV for GaAs, and ~5.5 eV for GaN, while 1D nanowires exhibit 20–35% smaller shifts due to partial carrier delocalization along the wire axis. Temperature effects are minor (~0.01–0.03 eV from 50–500 K), confirming that dimensional confinement is the dominant factor. These results provide quantitative guidelines for engineering tunable band gaps in LEDs, lasers, Si tandem solar cells, UV optoelectronics, and photodetectors, offering a predictive framework for IV, III–V, and II–VI semiconductor nanostructures.

A Systematic Analytical and Numerical Study of Incomplete Dopant Ionization in Germanium Over 4-400 K

M.Sh. Ibragimova — 2026-06-10

Incomplete dopant ionization critically influences the electrical properties of germanium (Ge), particularly under low-temperature and low-doping conditions relevant to advanced electronic and optoelectronic devices. In this work, we present a systematic numerical investigation of temperature- and concentration-dependent dopant ionization in Ge over the temperature range 4–400 K and dopant concentrations from 1×10¹⁴ to 1×10¹⁸ cm^-3. Ionization probabilities are evaluated for common acceptor dopants (Boron, Gallium, and Indium) and donor dopants (Phosphorus, Arsenic, and Antimony), with activation energies spanning 10–16 meV. The results reveal severe dopant freeze-out at cryogenic temperatures, where ionization probabilities drop below 0.1–0.2 for lightly doped Ge (N≤10¹⁵cm^-3), leading to carrier density reductions exceeding 80–90% compared to full-ionization assumptions. Donor dopants with lower activation energies achieve near-complete ionization (P(T)>0.9) at 100–150 K, while higher-energy acceptors require temperatures above 200–250 K. Increasing dopant concentration to 10¹⁷- 10¹⁸ cm^-3 significantly suppresses freeze-out, enabling ionization probabilities above 0.8 at temperatures as low as 50–70 K. At and above room temperature, all dopants exhibit near-unity ionization across the investigated concentration range. These findings provide quantitative guidelines for dopant selection and concentration optimization in Ge-based electronic, optoelectronic, and cryogenic devices, emphasizing the necessity of explicitly accounting for incomplete ionization in low-temperature device modeling and design.

Comparative Effects of Cold Plasma and Thermal Annealing on the Structural and Morphological Properties of Nickel and Iron Oxide Coatings

Aya Jumaa — 2026-06-10

This study comprehensively investigates and compares the effects of Cold Atmospheric Plasma (CAP) treatment as a potential alternative to thermal annealing on the structural and morphological properties of two distinct thin films: nickel (Ni) and iron oxide (FeₓOᵧ), both electrochemically deposited on ITO substrates. Characterization via X-ray diffraction (XRD) and atomic force microscopy (AFM) revealed that the material's nature dictates its response to post-processing. For nickel, short-duration CAP exposure (2.5-5 min) optimally enhanced crystallinity and surface smoothness by reducing grain size and roughness, while longer exposures led to oxidation and increased roughness. Conversely, for iron oxide, even brief CAP treatment initiated a transformation from a monocrystalline to a polycrystalline structure, forming a mixture of phases (Fe₃O₄, γ-Fe₂O₃). The smoothest iron oxide surface was achieved after 5-10 minutes of CAP, with excessive exposure (15 min) causing surface damage. Thermal annealing proved superior for nickel at 200 ^oC, yielding the smallest grains and smoothest surface. However, it was inadequate for optimal iron oxide crystallization. This work establishes CAP as a rapid, energy-efficient alternative to annealing, with its optimal parameters being highly material-specific, crucial for tailoring functional coatings in catalysis and sensing.

Incomplete Dopant Ionization Effects in GaN Optical Photovoltaic Converters Over 4–400 K for Space Solar Energy Applications

D.A. Qalandarova — 2026-06-10

We present a comprehensive numerical study of temperature- and concentration-dependent dopant ionization in GaN optical photovoltaic converters (OPCs), covering 4–400 K and doping levels from 1×10¹⁴ to 1×10¹⁸ cm⁻³. Acceptor dopants (Mg, Zn, Be) exhibit incomplete ionization at room temperature, with Mg achieving P_A≈0.60 at 300 K and severe freeze-out P_A < 1 below 50 K. Donor dopants (Si, O, S) are nearly fully ionized at 300 K P_D > 0.95 and maintain high electron density even at cryogenic temperatures. Increasing dopant concentration mitigates acceptor freeze-out but cannot overcome intrinsic activation limits at low temperatures. These results highlight the asymmetry between p- and n-type GaN, emphasize the importance of co-doping strategies, and provide quantitative guidance for predicting carrier densities, resistivity, and device performance in high-power, space-based GaN OPCs.

Determination of the Energy Spectrum of the Density of States Under Uniaxial Pressure

M.A. Rakhmanov — 2026-06-10

This paper considers the influence of hydrostatic pressure on the energy spectrum of the density of localized states in doped silicon n-Si, n-Si⟨Ni⟩ and p-Si⟨B,Mn⟩. Based on the experimental dependence of the relative resistivity ρ_p/ρ₀ on pressure, a model is constructed in which pressure enters via the deformation energy Ed = κP, yielding a linear shift of the trap levels E_i(P) = E_i(0)+αiEd. It is shown that for different impurity centers (Mn, Ni) the deformation sensitivity of the levels differs in both sign and magnitude, which is manifested in qualitatively different behavior of ρ_p/ρ₀(P). A procedure is proposed for reconstructing the relative electron concentration N(P)/N₀ and the associated spectrum N_ss(E,P) from the experimental ρ_p/ρ₀(P) curves. A comparison is made with the conventional temperature DLTS model, and the possibility of using a “tenso-DLTS” approach to identify donor and acceptor centers, their deformation potentials and symmetry is substantiated. The results demonstrate that hydrostatic pressure is not only an external perturbation, but also an effective spectrum-forming parameter for controlling the electronic properties of doped silicon.

Modeling the Density-of-States Spectrum Under Strain in Doped Silicon p‑Si

M.A. Rakhmanov — 2026-06-10

A deformation (strain) model of the spectrum of the density of localized states Nss(E,X) in p‑Si⟨B,Mn⟩ under uniaxial pressure X is presented. It is shown that the shifts of trap levels can be described by the deformation energy Ed = κX, a mechanical analogue of kT. At a fixed temperature T = 77 K, increasing X leads to a shift and restructuring of the spectrum: thermodonor (TD) levels move toward the conduction band, whereas manganese (Mn) levels shift toward the valence band, which agrees with the opposite trends observed in ρ(X) and μ(X).

Modeling the Impact of Incomplete Dopant Ionization on Built in Potential and C–V Characteristics of GaN p–n Junctions: A SCAPS-1D Study

Jo‘shqin Sh. Abdullayev — 2026-06-10

Incomplete dopant ionization in wide-bandgap semiconductors plays a critical role in determining carrier concentration, electrostatic properties, and overall device performance; however, its impact on GaN p–n junctions for optical photovoltaic converters (OPCs) remains insufficiently understood. In this work, SCAPS-1D simulations are employed to systematically investigate GaN p–n junctions incorporating three p-type acceptors (Mg, Zn, Be) and three n-type donors (Si, O, S) over doping concentrations of 10¹⁵–10¹⁸ cm⁻³ and temperatures ranging from 77 K to 400 K. The temperature dependence of the bandgap is described by the Varshni relation (R² = 0.9721), while dopant ionization is modeled as a function of both temperature and doping level to capture its effects on carrier distribution, the built-in potential, and capacitance–voltage (C–V) characteristics. The results reveal a pronounced reduction in junction capacitance at lower temperatures due to incomplete acceptor ionization. For a representative doping level of 5×10¹⁷ cm⁻³, the capacitance decreases from approximately 3.2 pF at 400 K to 1.5 pF at 77 K (≈53% reduction), primarily due to partial ionization of Mg acceptors, while donor species remain nearly fully ionized. These findings demonstrate that conventional models that neglect incomplete ionization significantly overestimate junction capacitance at low temperatures. Although the analysis is based on a one-dimensional framework, it provides physically consistent insight into the role of deep-level dopants and establishes a basis for future multidimensional TCAD investigations. This study highlights the necessity of incorporating incomplete-ionization effects into the design and optimization of high-efficiency, radiation-resilient GaN-based OPCs operating in extreme environments.

Investigation of Structural, Optoelectronic and Photovoltaic Performance of Cu₂SnS₃ Compound: Combined DFT and SCAPS-1D Simulations

Boualem Kada — 2026-06-10

Evaluating the structural, optoelectronic, and photovoltaic performance of the Cu₂SnS₃ compound is essential for the development of materials for solar energy. This ternary chalcogenide semiconductor stands out for its strong potential in photovoltaic applications, thanks to its broad light-absorbing range and chemical stability. In this paper, we have examined the structural and optoelectronic properties of copper-based ternary semiconductors, specifically those in the Cu₂SnS₃ compound, and their effectiveness in photovoltaic applications. Since there is significant variation in previous studies on the band gap values (0.65-1.35 eV), an attempt was made to find an appropriate approximation for studying this type of compound. The structural properties were investigated using both the Perdew-Burke-Ernzerhof (PBE) form of the generalized gradient approximation (GGA) and the local density approximation (LDA), allowing a comparative assessment of the effects of different exchange-correlation functionals on the material’s structure. Given the important influence that Cu delectrons play in determining their electronic properties, as shown by the results obtained when using different exchange correlation energy functionals. The combined function of the Becke-Johnson potential, modified by Tran and Blaha, and the Hubbard potential (TB-mBJ+U) was employed to systematically optimize the calculated anion displacement. The calculations yielded the band gap values. The semiconductor quasiparticle is 0.7 eV in the monoclinic structure (m-CTS; SG: Cc), and that of the orthorhombic structure (gold-CTS; SG: Imm2) is 0.73 eV, which is largely consistent with experimental values. The study of optical properties, including the dielectric function, also revealed the reflectance, absorption coefficient, and refractive index of the Cu₂SnS₃ compound in its two phases. The latter is considered a promising candidate in optoelectronic applications. To verify this, we used the SCAPS program, and the results were good. When this compound is used as an absorbent layer in a photovoltaic cell, the current density (Jsc) increases, peaking at a thickness of 800 nm.

Resistive Switching Behavior of Si/TiO Thin Films for Non-Volatile Memory Applications

Muradulla T. Normurodov — 2026-06-10

This study presents the fabrication of Si/TiO thin films deposited in DC mode via magnetron sputtering onto p-type silicon substrates and investigates their temperature-dependent resistive switching (RS) and low-resistance state (LRS) characteristics. The nanostructures were annealed at 420°C to improve crystallinity and interfacial contact. Electrical characterization through I–V measurements revealed clear bipolar RS behavior without the need for an initial forming process. The devices exhibited stable high-resistance (HRS) and low-resistance (LRS) states over multiple cycles. The switching mechanism is explained by the formation and rupture of conductive filaments induced by oxygen vacancies at the Si/TiO interface. Bandgap values obtained from Tauc plots were approximately 3.24 eV for TiO and 3.41 eV for SnO₂. These results confirm that Si/TiO nanothin films are promising materials for next-generation fast, energy-efficient, and rewritable memory devices.

Structural, Optoelectronic and Mechanical Properties of AHgCl3 (A=Rb, Cs) Perovskites: A First-Principles GGA and TB-mBJ Analysis

Habiba Bouheraoua — 2026-06-10

The structural, mechanical, and optoelectronic characteristics of the cubic halide perovskites AHgCl₃ (A=Rb, Cs) are calculated employing density functional theory (DFT) utilizing the full-potential linearized augmented plane-wave (FP-LAPW) method with various exchange-correlation potentials through the Wien2k software. The cubic stability of the anticipated compounds was validated using the Goldsmith tolerance factor and the octahedral factor. Furthermore, to verify their thermodynamic stability, we evaluated the formation energy. The calculated elastic constants, including Poisson's ratio, Pugh's ratio, and Cauchy pressure, indicate that the investigated perovskites have mechanical stability while also exhibiting ductile properties and ionic bonding. Furthermore, we have utilized the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential to assess optoelectronic features. Our calculations indicate that both compounds function as indirect band-gap semiconductors of 1.25 eV for RbHgCl₃, and 1.16 eV for CsHgCl₃. Additionally, optical characteristics are computed within the energy spectrum of 0 eV to 20 eV. These compounds exhibit strong optical absorption in the ultraviolet range and low reflectance value at zero photon energy. This optical performance indicates that both halide perovskite compounds possess analogous features and are appropriate for optoelectronic applications, especially in photovoltaic devices and ultraviolet photodetectors.

A Numerical Simulation Study Investigating the Functionality of a Perovskite Solar Cell Based on FASnI3 in Both Conventional and Inverted Configurations Using Compatible Zn(O0.3S0.7) as the Electron Transport Layer

M.V. Kavitha — 2026-06-10

Formamidinium Tin Iodide is a promising candidate as an absorber layer in perovskite solar cells due to its tunable bandgap, high absorption coefficient, and good thermal stability. The selection of suitable charge transport layers providing the proper band offset can effectively reduce the recombination at the interfaces and improve the performance of solar cells. The study focuses on enhancing the performance of a perovskite solar cell in which Formamidinium Tin Iodide (FASnI₃) is the absorber layer, Zn(O_0.3S_0.7) is the ETL and Spiro-OMeTAD is the HTL using numeric simulation. These charge transport layer materials are selected on the basis of their adequate energy band alignment with the absorber. The structure Glass substrate/FTO/Zn(O_0.3S_0.7)(ETL)/FASnI₃/Spiro-OMeTAD(HTL)/Au, which is an unexplored combination in n-i-p architecture, is simulated through SCAPS-1D and optimization of cell parameters- absorber thickness, absorber doping concentration, absorber defect density, ETL thickness, ETL defect density, HTL thickness, and HTL defect density- is carried out. The variation of cell performance parameters with interface defect density and temperature is also analyzed. With this optimization, the cell delivers an open circuit voltage(V_oc) = 1.0145V, short circuit current density (J_sc) = 37.82mA cm^-2, fill factor (FF) = 83.31% and Power Conversion Efficiency(PCE) =31.97%. The optimized parameters are used to simulate the p-i-n inverted architecture, and the cell output is as follows.V_oc= 1.0919V, J_sc = 37.293mA cm^-2, FF = 83.01% and Power Conversion Efficiency(PCE) =33.8%.

Analysis of Thermo-Magnetic Casson Hybrid Nanofluid Flow Over a Porous Stretching Sheet Considering Chemical Reaction Using RSM

Esara Sivasankar — 2026-06-10

Thermophysical analysis of heat and mass transmission has many potential uses in solar collectors, chemical reactors, medicinal devices, and sophisticated cooling systems, among other applications. Owing to this incentive, the present work often employs response surface methodology for heat and mass transfer analysis of a Casson hybrid nanofluid over a permeable stretching sheet with convective and radiative effects. The control system of the PDEs defining the developed model is transformed into a coupled set of nonlinear ODEs by applying appropriate similarity transformations. The shooting method, implemented with MATLAB's BVP4c solver, is used to numerically integrate these simplified equations. Using tabulated data and graphical representations, the effects of relevant physical parameters on the distributions of velocity, temperature, and concentration are systematically examined. Additionally, Response Surface Methodology is used to statistically evaluate key response variables across a broad range of governing parameters, such as the skin-friction coefficient, heat, and mass-transfer rates. The findings show that increasing the Casson parameter reduces the temperature profile because the fluid's effective yield stress decreases. Furthermore, due to increased Lorentz forces, a higher magnetic field considerably reduces fluid velocity. Additionally, it has been observed that an increased solid volume fraction raises the nanofluid's temperature due to enhanced thermal conductivity. The statistical analysis indicates that the mass-transfer accuracy for the derived mathematical model in kerosene is 99.85%.

MHD Duct Flow of Nanofluid Influenced by a Dual Heat Source in the Presence of an Electric Field (E0) and a Magnetic Field (B0)

Bishnu Ram Das — 2026-06-10

The flow of copper (Cu), silver (Ag), titanium oxide (TiO₂), copper oxide (CuO) nanoparticles with water as a base fluid in the presence of a high magnetic field in a vertical rectangular duct are examined in this research. The duct's left and right walls are kept at various steady temperatures and concentrations. The temperature, velocity, and nanoparticle concentration fields are all described by the transport equations. The second-order upwind method, an explicit finite-difference method (EFDM), is used to discretize the coupled nonlinear Navier-Stokes equations. To examine the heat transfer efficiency of this nanofluid, we nondimensionalized the governing equations and obtained solutions using an explicit numerical scheme. MATLAB code is used to perform computational steps. We have plotted the velocity, temperature, and concentration fields for different values of the magnetohydrodynamic (MHD) flow parameters, including the thermal Grashof number (G_r), solutal Grashof number (G_c), Hartmann number (H_a), electrical field load parameter (E), Brinkman number (B_r), and nanoparticle volume fraction (ϕ).

Computational Modeling of the Structural Stability of Metal Nanoclusters Based on the Molecular Dynamics Method

Akbarali M. Rasulov — 2026-06-08

The paper examines the results of molecular dynamics modeling of metallic clusters of copper (Cu), silver (Ag) and cobalt (Co). The focus was on how the geometric properties and energetic stability of nanoclusters vary with size. Numerical calculations were performed using the Lammps software suite. This software package is widely used for atomistic modeling tasks and has proven itself in the study of systems with a large number of particles. The interatomic interactions were described using EAM and MEAM potentials, and the simulations were performed in a high-performance computing environment with MPI/OpenMP support. The work was conducted in two sequential stages. In the first stage, the clusters were relaxed at a temperature of 0K to obtain configurations corresponding to the minimum energy state. The systems were then gradually heated to 300K, which made it possible to trace changes in their stability and assess possible structural rearrangements during thermal evolution. The computational results showed that as the number of atoms increases, the overall geometry of the clusters approaches a spherical shape, and the system's energetic stability is enhanced due to the increase in the volume of the inner atoms. We present a systematic MD simulation study of structural evolution and energetic stability in Cu, Ag, and Co nanoclusters comprising 13 to 55 atoms. By identifying magic-number clusters and comparing compositional behavior from 0K to 300K, we reveal distinct size-dependent stability trends across the three metals. These findings offer quantitative insight into nanocluster formation mechanisms relevant to catalysis and nanomaterial engineering.

Structural Transitions in Cu₁.₈₅S Single Crystals

J.I. Ismayilov — 2026-06-10

Cu_1.85S is of significant current interest due to its complex crystal chemistry, wide homogeneity range, and unique physicochemical properties. These materials belong to the class of digenites and exhibit various structural transformations and reversible phase transitions that are highly sensitive to copper content. The synthesis, growth, and investigation of the structural behavior of Cu_1.85S single crystals provide essential insights into phase stability and transformation mechanisms in the Cu_2-xS system. Such knowledge is crucial for potential applications in semiconductor devices, catalysts, and energy conversion systems, where the crystal structure and phase composition directly influence material performance. This paper presents the results of the synthesis, growth of single crystals, and X-ray phase analysis of the nonstoichiometric compound Cu_1.85S, which belongs to the class of digenites. The single crystals were obtained by combining the Bridgman directional crystallization method with slow cooling. A comprehensive microstructural and X-ray analysis was carried out, including the use of Weissenberg photographs and temperature-dependent diffraction studies in the range from room temperature to 420℃. It was established that at room temperature, the Cu_1.85S sample is biphasic and consists of orthorhombic (P_nma) and monoclinic ( ) phases. Upon heating, two structural transitions were observed: first to a tetragonal phase at approximately 93℃, and then to a high-temperature face-centered cubic (FCC) lattice at around 120℃. All transitions are reversible and occur via a single-crystal-to-single-crystal mechanism with well-defined orientational relationships between the lattices. The biphasic nature at room temperature is attributed to the accumulation of copper atoms in twin regions. This work contributes to understanding structural transformations in the Cu_1.85S system and confirms the existence of stable interphase transitions that depend on copper content.

Structural Study of Copper Doped Single-Crystal Silicon by Diffusion

Akramjon Y. Boboev — 2026-06-10

The paper presents the results of a structural study of single-crystal silicon doped with copper by thermodiffusion at 1423K. The object of the study was n-Si crystals grown by the Czochralski method, containing SiO₂oxygen precipitates. Structural analysis was performed on an X-ray diffractometer with an improved optical scheme, which made it possible to detect weak additional reflections and changes in lattice parameters. It was established that copper doping leads to the appearance of elastic stresses in the surface layers of the crystal, a change in the interplanar distance (111) and a redistribution of the intensities of reflections (222) and (333). Diffuse scattering and additional selective reflections were detected, indicating the formation of new phases. For the first time, a direct structural method has shown the formation of CuO nanocrystals with a monoclinic structure and an average size of 14–14.5 nm and Cu₂O nanocrystals with a cubic structure and an average size of about 17 nm. Their lattice parameters were measured experimentally and are slightly different from the standard reference values, which shows that the silicon matrix and internal stresses affect their structure. It has been shown that SiO₂ oxygen precipitates create local elastic fields that promote diffusion, nucleation, and separation of copper in the form of oxide nanophases. The results obtained clarify the mechanism of structural transformations in copper-doped silicon.

Finite Element Modeling of Scanning Speed Effects in Femtosecond Laser-Induced Graphene Fabrication

J.O. Sadullayev — 2026-06-10

Laser-induced graphene (LIG) enables mask free direct writing of conductive carbon structures on polyimide substrates for flexible electronic and sensing applications. In femtosecond laser-induced graphene (FLIG), the scanning speed strongly affects the local temperature field, and thus the extent and quality of graphitization, but this dependence is still not fully quantified. In this study, a time dependent finite element model is implemented in COMSOL Multiphysics to resolve the temperature distribution generated by a femtosecond laser beam on a polyimide surface as a function of scanning speed. The laser is described as a moving Gaussian surface heat source, and the transient heat conduction equation is solved to capture ultrafast heating and cooling during a pulse train. Simulations for scan speeds between 0.05 and 0.20 m/s show that decreasing the speed increases the peak temperature and enlarges the heat affected zone, whereas higher speeds reduce both quantities. By comparison of the predicted peak temperatures with the graphitization thresholds in the literature for polyimide derived graphene, an intermediate scan speed window is identified in which the thermal budget is sufficient for graphene formation while avoiding excessive overheating and damage. This modeling framework provides a practical tool for pre selecting femtosecond laser parameters and for accelerating the optimization of FLIG processes for flexible graphene based devices.

Modeling the Effect of Co-Ion Implantation on ZnO, Mg-Doped ZnO Thin Films Using Monte Carlo SRIM

Akramjon Y. Boboev — 2026-06-10

The interaction behavior of 1.25 MeV Co ions with Si, ZnO, and Mg-doped ZnO (ZnO:Mg) targets has been systematically analyzed using the latest SRIM 2013 simulations. The findings show that atomic displacements, the production of vacancies and energy loss are greatly influenced by the composition and structural density of the target. The results reveal that the highest defect concentration is seen in crystalline Si due to its lower displacement threshold energy and smaller atomic mass, which increases the likelihood of recoil collisions. On the other hand, ZnO shows moderate defect generation as its high atomic density and bonding energy make it harder for the lattice to be disordered. Moreover, the presence of Mg in the ZnO matrix reduces the overall damage slightly, meaning the lattice is more stable and tolerant to radiation. It can be inferred from these results that Mg doping does indeed improve the structural robustness of ZnO against high-energy Co-ion bombardment and thus makes ZnO:Mg films more appropriate for radiation-resistant optoelectronic and sensing applications.

Study of Thermophysical Properties of Cu₂NiTe₂ Compound at High Temperatures by DSC Spectroscopy

Y.I. Aliyev — 2026-06-10

The crystal structure and thermophysical properties of the chalcogenide semiconductor Cu₂NiTe₂ were comprehensively investigated using X-ray diffraction and differential scanning calorimetry. Structural characterization at room temperature revealed that the synthesized compound crystallizes in the hexagonal crystal system with the space group P6₃/mmc, indicating the formation of a highly ordered polycrystalline phase. The diffraction peaks were sharp and well-defined, confirming the material's good crystallinity and structural homogeneity. The absence of additional impurity peaks in the diffraction pattern also suggests that the synthesized compound possesses a predominantly single-phase structure.

Fabrication and Electrical Transport Properties of Triple-Barrier GaAs-BASED M–p–n–M Structures

Bahodir M. Abdukahhorov — 2026-06-10

Engineering multi-barrier potential profiles provides an effective approach to controlling charge-carrier transport in semiconductor structures. In this work, three configurations of triple-barrier GaAs-based metal–p–n–metal (M–p–n–M) structures were fabricated on semi-insulating GaAs substrates using liquid phase epitaxy (LPE). The layer composition and semitransparent metal contacts (Ag, Au) were deliberately designed to form a coupled system of metal–semiconductor and p - n junctions. The electrical transport properties were investigated over a wide voltage range, and the current–voltage characteristics were comparatively analyzed. In the low-bias regime, the current follows a power-law dependence I ~ V^0.5, indicating generation-dominated transport. With increasing bias, a transition to a quasi-ohmic region and subsequent breakdown behavior was observed. In the high-field regime, linear regions in the ln(I/U²) versus 1/U dependence confirm the dominance of field-assisted transport mechanisms within the barrier regions. The results demonstrate that electric-field redistribution and barrier coupling play key roles in governing charge transport in triple-barrier structures, providing a foundation for the further development of advanced semiconductor devices.

Structural and Phase States of Rhodium Doped Silicon Monocrystals

Akramjon Y. Boboev — 2026-06-10

In this paper, the structural and phase states of silicon (Si) monocrystals doped with rhodium (Rh) atoms were investigated. For the study, n-type silicon samples doped with rhodium, grown by the Chokralsky method, were selected. Rhodium atoms were introduced via thermal diffusion at 1300°C, and the samples were cooled under both slow and rapid cooling regimes. The resulting data were evaluated using X-ray diffraction (XRD) analysis. In the control samples, heat treatment resulted in the formation of secondary phases such as SiP₂ and SiO₂, which were shown to be associated with background impurities, particularly oxygen atoms. In the rhodium-alloyed and slow-cooled sample, the SiRh₃ phase formed, and the crystal lattice remained relatively stable. This indicates that the rhodium atoms have the ability to reduce internal stresses and relax the lattice. In the rapid cooling regime, the RhO₂ oxide phase appeared, and an increase in micro-stresses and crystal defects was observed. The results indicate that rhodium doping is an effective method for controlling the structure, phase composition, and electrical properties of silicon monocrystals. This research is of significant importance for semiconductor materials, microelectronics, and solar cells.

Thermodynamic Properties of Mn-Doped Diluted Magnetic Semiconductor Superlattices

Mehdi M. Mahmudov — 2026-06-10

This work investigates the thermodynamic properties of a two-dimensional electron gas in manganese-doped diluted magnetic semiconductor superlattices, with particular emphasis on the chemical potential. Within the grand canonical formalism, a general expression for the chemical potential is derived that is valid for both degenerate and nondegenerate cases. In the nondegenerate limit, the chemical potential decreases with increasing temperature and exhibits a logarithmic dependence on carrier density; the temperature sensitivity is most pronounced at low carrier concentrations, where entropic effects dominate. In the degenerate regime, Landau quantization leads to a characteristic stepwise oscillatory dependence of the chemical potential on the applied magnetic field. The influence of the exchange interaction is analyzed in two limiting cases: in the weak-coupling limit, the correction to the chemical potential is linear in the concentration and exchange constant, whereas in the strong-coupling limit, the system approaches complete spin polarization with carriers confined predominantly to a single spin channel. The exchange interaction introduces an additional spin-dependent contribution described by the Brillouin function, resulting in the most pronounced modifications at low temperatures and in strong magnetic fields.

Electronic Transitions and Recombination Mechanisms Cu-Doped CdIn₂S₄ Single Crystals

Zafar Kadiroglu — 2026-06-10

The study investigates the spectral distribution of photoconductivity, optical quenching, transient characteristics, thermally stimulated currents, and the temperature dependence of both dark and photocurrent in Cu-doped CdIn₂S₄ single crystals. Detailed analysis of the experimental data reveals the presence of deep donor levels with ionization energies located at Е_с - 0.17 eV, Е_с - 0.66 eV, Е_с - 1.2 eV, and Е_с - 1.55 eV. At 110 K, optical quenching of the photoconductivity was observed within the photon energy range of 0.86 to 1.63 eV. The energy positions of the photosensitivity centers relative to the valence band maximum were identified, yielding optical ionization energy of E^o_vr = 0.86 eV and a thermal ionization energy for the r-type levels of E^t_vr = 0.62 eV. The capture cross-sections ratio for holes and electrons at these r-centers was found to be S_pr/S_nr = 5×10⁴. Both optical and thermal quenching phenomena are attributed to charge-state transitions and carrier-exchange dynamics between slow (r) and fast (s) recombination centers. The well-defined electronic structure and high photosensitivity of Cu-doped CdIn₂S₄ single crystals suggest they are promising candidates for advanced photodetector applications in the visible and near-infrared spectral regions.

An In-Depth First-Principles Study of the Structural, Stability, Electronic, Thermodynamic, and Optical Characteristics of Two-Dimensional BiBrO

Yadgar Hussein Shwan — 2026-06-10

This study leverages DFT within the GGA framework to provide a thorough calculate of the stability, electronic properties, thermal performance, and optical responses of 2D BiBrO. The computed formation energy, along with phonon calulation findings and AIMD results, verifies the stable structural, dynamical and thermal stability of the BiBrO system. The 2D BiBrO material exhibits semiconducting behavior with a band gap of 2.42 eV, as confirmed by electronic band structure analysis. Optical properties analysis of BiBrO reveals powerful visible and ultraviolet (UV) light interaction, which supports its applications as a solar energy storage device. The large ability of BiBrO to store thermal energy is due to high heat capacity, because BiBrO has a greater phonon density of states. The entropy rises proportionally to the temperature which means that there is additional atomic disorder and more accessible microscopic states. Furthermore, the increase in entropy and the plateau in heat capacity at high temperatures imply a change toward a more disordered state, while yet allowing for effective thermal energy absorption. The low lattice thermal conductivity and smaller phonon group velocity of BiBrO are the characteristics that render the material useful in thermal insulation, while maintaining structural stability. These findings give critical information regarding how BiBrO may be used in energy storage systems as well as thermal barrier.

Comprehensive Analysis of Morphology, Structure, and Photovoltaic Properties of CdTe and CdTe:In Thin Films

Iftikhorjon I. Yulchiyev — 2026-06-10

In this work, the photovoltaic properties and short-circuit current spectra of indium (In)-doped CdTe films were comprehensively investigated. The study covers the spectral sensitivity and light-absorption characteristics of undoped, freshly prepared, and thermally treated CdTe:In films. The effects of doping level and thermal treatment temperature on photovoltaic effect parameters were analyzed. The results showed that indium doping and subsequent thermal treatment significantly improve the photovoltaic efficiency of CdTe films. Using spectroscopic and electron microscopy methods, the chemical composition, surface morphology, and bandgap width of the films were determined, and their interrelation with optical and electrical properties was revealed. The obtained results indicate that films are promising for applications in solar energy devices.

Theoretical and Experimental Analysis of Mixed Exciton-Polariton Luminescence in CdS Crystals in the Regime of Strong Exciton Damping

Bozorboy J. Akhmadaliev — 2026-06-10

This work presents a combined theoretical and experimental study of mixed exciton-polariton luminescence in anisotropic crystals in the regime of strong exciton damping near the A-exciton resonance. A spatially dispersive model of radiative mixed modes is used to analyze the transformation of the spectral contour, peak position, partial modal contributions, and angular dependence of the linewidth. Calculated spectra for emission angles from to are compared with photoluminescence measurements, and good agreement is obtained at K for meV and μm. Unlike conventional approaches that relate the transition to a Lorentzian emission profile only to the condition , we show that this regime additionally requires the transport-related constraint Under these combined conditions, the mixed-mode emission contour approaches a quasiclassical Lorentzian profile with a half-width close to . At the same time, spatial dispersion and intermode interference are not fully suppressed in anisotropic crystals and become more pronounced at larger emission angles or smaller effective diffusion lengths. The results provide a refined criterion for identifying the quasiclassical emission regime and a practical framework for extracting exciton damping and effective diffusion depth from experimental spectra.

Synthesis and Thermoelectric Properties of TuSnSe₂ Compound

Razim Bayramli — 2026-06-10

In this research work, the interaction of the SnSe-TuSe system was studied, and as a result of complex physicochemical analyses, the solubility region of TuSe in SnSe (75-100%) was determined. It was also determined that the TuSnSe₂ compound was obtained in a 1:1 ratio of its components, and a phase diagram of the system was constructed. X-ray structure and differential thermal analysis of the sample showed that this compound crystallizes in a hexagonal syngony. Some kinetic parameters of the triple compound TuSnSe₂ were determined at room temperature. Electrical conductivity (σ), thermo electromotive force (e.m.f.) (α) and thermal conductivity (χ) were studied in the temperature range T=300÷800K. In order to determine the variation in the charge carrier scattering mechanism the temperature dependences of the Hall mobility and electrical conductivity of this compound were also investigated. Based on the sign of the thermo-electromotive force and the Hall coefficient, it was determined that the conductivity in this compound is n- type. Based on the obtained results, it was determined how the concentration of charge carriers and the Hall mobility changed. Anomaly changes are observed in the temperature dependence of the electrical conductivity, thermoelectric potential and total thermal conductivity in the temperature interval T=460÷500K.

Temperature Dependence of the Main Parameters Determining the Interband Absorption Spectrum of a Si:H

Rustamjon G. Ikramov — 2026-06-10

In this work, the temperature dependence of the interband optical absorption coefficient of hydrogenated amorphous silicon (а-Si:H) has been investigated both experimentally and theoretically. By fitting the values obtained from the optical absorption coefficient formula, the temperature dependence of the characteristic vibration energy of а-Si:H was studied using the Bose-Einstein and Varshni formulas.

Electromagnetic Properties of a Hybrid Solid-State Structure Incorporating a Plasma-Like Medium and a Metasurface

N.N. Beletskii — 2026-06-10

In this paper, we theoretically investigate the dispersion properties of surface and bulk-surface electromagnetic waves propagating in a hybrid layered solid-state structure containing an isotropic plasmonic metasurface. This structure consists of a semi-infinite dielectric 1, an isotropic metasurface, a dielectric layer 2, and a semi-infinite plasma-like medium. We derive an exact analytical dispersion relation for the coupled electromagnetic modes and perform a comprehensive numerical analysis of it. Our analysis demonstrates how the metasurface conductivity, the dielectric layer thickness, and the semiconductor plasma frequency significantly influence the resonant interaction of the surface waves. It has been revealed that adding a plasma-like medium as a substrate leads to the emergence of hybrid surface waves and the possibility of bulk-surface waves. In fact, we found a significant difference between metal and semiconductor substrates. Indeed, to obtain exactly the same splitting value in a system with a metal substrate, a dielectric spacer approximately seven times thicker is required. This geometry difference makes semiconductors a much more practical choice for deep subwavelength miniaturization. The results provide a theoretical basis for the development and optimization of novel tunable waveguides, sensors, and slow-wave devices operating in the microwave and terahertz frequency ranges.

Ambipolar Diffusion and Electric Field Reversal in Electronegative Plasma with Charged Nanoparticles

V. Lisovskiy — 2026-06-10

An analytical model of ambipolar diffusion in plasma consisting of electrons, positive ions, negative ions, and negatively charged nanoparticles is proposed. Analytical expressions are derived for the ambipolar diffusion coefficients of all charged species, as well as for the ambipolar electric field strength. In plasma containing only electrons, positive ions, and negative ions, high concentrations of negative ions lead to a transition from ambipolar to free diffusion, where the ambipolar diffusion coefficients approach the corresponding free diffusion coefficients. In plasma consisting of electrons, positive ions, and negatively charged nanoparticles, high nanoparticle concentrations result in qualitatively different behavior: the ambipolar diffusion coefficient of electrons approaches twice the free electron diffusion coefficient, while the ambipolar diffusion coefficient of positive ions approaches twice the free diffusion coefficient of nanoparticles. For the general four-component plasma, the ambipolar diffusion regime is governed by the dominant electron-loss mechanism, namely, electron attachment to either electronegative gas molecules or nanoparticles. If electron attachment to gas molecules dominates, the ambipolar diffusion coefficients of electrons, negative ions, and nanoparticles remain close to their free diffusion coefficients. In contrast, when electron attachment to nanoparticles dominates, these coefficients approach twice the corresponding free diffusion coefficients. The ambipolar diffusion coefficient of positive ions was found to depend strongly on the dominant negatively charged species in plasma. Under intensive negative-ion formation, it approaches the free diffusion coefficient of negative ions, whereas in plasma dominated by electron attachment to nanoparticles it asymptotically approaches twice the free diffusion coefficient of nanoparticles. It is shown that sufficiently high concentrations of negative ions and/or charged nanoparticles substantially reduce the ambipolar electric field strength and may even reverse its sign. A weakly negative ambipolar electric field can remove excess negative ions and nanoparticles from plasma, thereby stabilizing the discharge. Experiments with acetylene plasma demonstrated intense transport of small nanoparticles toward the tube walls, which may serve as indirect evidence of an ambipolar electric-field reversal.

Structural, Morphological and Electrochemical Properties of NaFeO₂ Synthesized by Solar Melting

M.S. Payzullakhanov — 2026-06-10

This paper presents the synthesis of tetragonal sodium ferroxide (NaFeO₂) via a solar-furnace melting method. The resulting material is characterized by a quasi-spherical morphology, an average particle size of ~1.2 μm, high crystallinity (⁓ 92%), and a polydisperse distribution, which ensures efficient transport pathways and uniform electrolyte penetration. SEM analysis revealed the formation of porous aggregates of nanogranular particles (200-500 nm) with a developed specific surface area (5-10 m²/g). DTA/TGA demonstrates multistage thermal transformations of the Na₂CO₃+Fe₂O₃ system with the formation of NaFeO₂ at 800-850 °C, confirming the thermal stability of the material. X-ray diffraction analysis confirmed the high crystallinity of the tetragonal phase with parameters a=4.47 Å, c = 14.4 Å, and a coherent scattering region size of ⁓ 28 nm. The obtained data indicate the high structural stability and electrochemical activity of NaFeO₂, making it promising for use in sodium-ion batteries.

Formation and Extraction of H– Ions from Penning Discharge with Metal Hydride Cathodes in LMF and HMF Modes

Ihor Sereda — 2026-06-10

The use of metal hydride cathodes in Penning discharges offers a promising approach to the efficient production of negative hydrogen ions under low- and ultralow-pressure conditions. In this work, we summarize and extend our experimental studies on the influence of metal hydride elements on the characteristics of Penning discharge with axial extraction of negative ions. At low residual pressure, the introduction of metal hydride cathodes enables plasma generation exclusively from hydrogen released by the cathode material, without any external gas injection. This feature opens the way to the development of compact, gas-feed-free ion sources with excellent gas utilization. The negative ions extraction mechanism is shown to depend strongly on the operating mode of the Penning discharge, determined by the magnetic field strength. In the low magnetic field mode, the expansion of the anode layer toward the discharge axis and the associated negative space charge suppresses efficient extraction, limiting it mainly to paraxial ions and those formed near the extraction aperture. In contrast, in the high magnetic field mode, the anode layer becomes thin, and the central plasma region is essentially field-free, enabling the extraction of negative ions from the entire discharge cross-section. Furthermore, the effect of increasing the anode diameter is investigated. Enlarging the anode diameter increases the plasma volume surrounding the metal hydride cathodes, leading to improved plasma uniformity, more homogeneous cathode heating, and a more uniform hydrogen release. These effects enhance the conditions for negative ions formation and result in a higher extracted current. The results demonstrate the feasibility and advantages of metal-hydride-based Penning ion sources for efficient production of negative ions under low-pressure operation.

Structural, Morphological, And Optical Properties of ZnO Thin Films Grown on Si Substrates via Ultrasonic Spray Pyrolysis

Azim K. Soatov — 2026-06-10

Based on scientific sources presenting modern semiconductor device fabrication technologies and growth methods, the influence of external factors on ZnO samples was evaluated through various approaches. In this work, ZnO thin films were grown on Si substrates using the ultrasonic spray pyrolysis (USP) method. The physical characteristics of the obtained samples, including the optical bandgap energy and in-situ laser Raman spectroscopy measurements, were investigated. The primary objective of this study was to synthesize ZnO thin films with precise nanometric thicknesses on silicon (Si) substrates and to investigate the influence of substrate temperature, precursor composition, and evaporation rate. Using Ellipsometry, XRD, and SEM, we characterized the film thickness, crystal lattice structure, and morphological evolution during growth.

Optimization of Multilayer Graphene-Based Absorbers Under H-Polarization via Differential Evolution in a Hybrid Computing Environment

Mstyslav E. Kaliberda — 2026-06-10

A computationally efficient framework for optimizing multilayer radar-absorbing structures based on periodic planar gratings of resistive strips embedded in a dielectric slab is presented for the H-polarization case. The electromagnetic response is modeled using a rigorous singular integral equation (SIE) formulation combined with an operator-based cascading technique, providing high numerical accuracy and stability with low computational cost. This ultra-fast forward solver is integrated into a parallel differential evolution (DE) optimization framework implemented in a client–server architecture, enabling efficient solution of high-dimensional inverse design problems. The optimization targets broadband absorption under normal incidence while preserving optical transparency, with graphene used as a representative resistive material. Numerical results demonstrate effective suppression of resonance-induced spectral holes and stable, wideband absorption in multilayer structures with 10 layers, showing robustness under fabrication-inspired constraints and oblique incidence.

Radiation Embrittlement of Tantalum Coating of the Neutron Source Targets

O.O. Parkhomenko — 2026-06-10

The works in the field of radiation materials science of targets for neutron sources based on subcritical assemblies driven with linear accelerators of electrons or protons, the so-called ADS systems, are presented. Currently, electronuclear ADS systems are prototypes of safe 5th-generation nuclear reactors. In connection with the physical start-up of the neutron source installation of the NSC KIPT the target of which is made of tungsten coated with tantalum, the effect of radiation on mechanical properties is considered, and the resource of the tantalum coating of the target is estimated.

Application of Semi-Empirical Models of Electron Beam Control in Radiation Sterilization Technology

Valentín T. Lazurik — 2026-06-10

An application of semi-empirical models involves analyzing data regularly recorded during irradiation control and processing it to determine the values of the semi-empirical model parameters. In the present paper, the recorded data used present the depth dose curves measured at the INCT radiation sterilization center in Warsaw, Poland. The measurement method is described. The depth dose curves are analyzed using the dosimetric wedge method. The characteristics of the depth dose curves are presented. The depth ranges are determined within which the measurement results can be used without special processing as depth dose curve values in the dosimetric wedge. Special procedures are developed to approximate and extrapolate the measurement results. The objective of the procedures is to obtain the basic dependencies of semi-empirical models, namely the doses as a function of depth at normal incidence of the electron beam on a semi-infinite medium. Special procedures are developed to process measurement results using the PFSEM method (two-parameter fitting of a semi-empirical model of depth-dose curves). A procedure for excluding bremsstrahlung contributions from depth-dose curves is proposed and implemented. The value of this contribution is estimated as the average dose in the bremsstrahlung tail region. The change of the bremsstrahlung influence on the doses with depth is neglected. The method for selecting the values of model-fitting parameters is proposed based on the assumption that the fitting parameters depend weakly on electron energy. Based on the proposed method, the fitting parameters of semi-empirical models are determined from Monte Carlo simulations of depth-dose curves during irradiation of a layer with a monoenergetic electron beam. The measurement results are compared with depth-dose curves calculated using semi-empirical models for electron-beam irradiation at different angles of incidence on an aluminum dosimetric wedge. Based on the comparison results, the errors in model predictions and the feasibility of implementing methods to optimize irradiation processes by selecting the angle of electron incidence on the surface of the irradiated object are discussed.

Morphological Features and Microstructural Characteristics of Craters on the Surface of Industrial Aluminum Alloy AA6111 Irradiated with a High-Current Pulsed Electron Beam

V.V. Bryukhovetsky — 2026-06-10

Irradiation of the industrial aluminum alloy AA6111 with a high-current pulsed electron beam (HCPEB) with particle energy of 0.35 MeV, a beam current of 2.0 kA, a pulse duration of 5 μs, and a beam diameter of 3 cm results in the formation of a surface layer with improved physical and mechanical properties. However, the potential formation of craters on the surface of HCPEB-treated materials is one of the negative effects caused by HCPEB. This study examines the types and morphology of craters formed on the surface of AA6111 aluminum alloy after irradiation with HCPEB. The distribution of crater sizes and the crater density on the irradiated surface were studied. An analysis of the elemental composition of the crater walls and the adjacent melted surface was performed. The features of the grain microstructure, including shape and size, in the crater area were studied. The implications of these observations for a deeper understanding of the mechanisms underlying crater formation during HCPEB irradiation are discussed.

Comparison of Sn and as Effect on Tensile Properties of Pb–3.5%Sb Grid Alloy for Lead-Acid Batteries

Victor O. Dzenzerskiy — 2026-06-10

In this work, the effects of 0.5 wt.% Sn and 0.16–0.23 wt.% As on tensile properties of Pb–3.5%Sb grid alloy for lead-acid batteries were compared in the as-cast condition. The alloys were melted under different cooling-rate conditions in a casting mold preheated between 50°C and 170°C, with cooling rates ranging from 100 °C/s to 50 °C/s. Mechanical properties, such as ultimate tensile strength and percentage elongation, were measured at room temperature using the TIRAtest 2300 universal testing machine at a constant crosshead speed of 10 mm/min. It was established that as mold preheating temperatures rise, the elongation and ultimate tensile strength of the Pb–3.5%Sb–0.23%As alloy decrease by 13.9% and 11.8%, respectively. Addition of tin in place of some arsenic causes a decrease in ultimate tensile strength of the Pb–3.5%Sb–0.5%Sn–0.16%As alloy, but only by 2.8 %, whereas elongation increases by 2.4 %. It was concluded that additions of tin compensate for the negative effect of arsenic on the tensile properties of the Pb–3.5%Sb grid alloy, which relates to the formation of brittle arsenic-containing phases at the grain boundaries. Tin addition to the Pb–3.5 %Sb alloy produces higher tensile properties at room temperature than those obtained by the addition of arsenic.

Characteristics of Radiated Fields Formed by Patch Antenna with Complicated Aperture

Sergey A. Pogarsky — 2026-06-10

The paper considers issues related to simulating the electrodynamic characteristics of a patch antenna based on a microstrip disc resonator with a complex topology of the radiating aperture in the form of three slot log-periodic discontinuities, oriented at the angle of 120⁰with the scaling factor τ=0.8 and the spacing factor σ= 0.15. Three concentric ring slot discontinuities are located in a grounded base at a certain distance from the dielectric substrate, the centers of which coincide with the center of the microstrip disc. The antenna was fed by a section of a coplanar line with a stepped profile of the central conductor. The calculations used a model based on two methods: the magnetic wall model (semi-open resonator model) and the finite element method. After optimization procedures were carried out for the selected parameters, it was established that compromise parameter sets were necessary to obtain the required characteristics

Formation of an Axially Symmetric Field Distribution Using Rectangular Aperture Radiators

I.K. Kuzmychov — 2026-06-10

Using the aperture method, radiation from the open end of a rectangular waveguide was studied. Expressions were derived to describe the radiation pattern of such an aperture in the far-field region in two mutually perpendicular planes. Numerical studies of the radiation pattern cross-sections in the image plane were performed for two rectangular apertures, 40×33 mm and 30×21.6 mm, with varying aperture widths and heights. A comparison of the obtained radiation pattern cross-sections with a Gaussian field distribution showed that up to the –11 dB level, the radiation pattern cross-sections in both image planes practically coincide with the Gaussian field distribution. This result is particularly important when a wave beam is incident on the flat face of an axicon. It was also shown that varying the smaller dimension of the rectangular aperture can yield an axially symmetric radiation pattern. Experimental studies of these apertures in the K_a band were conducted. Good agreement between the experimental results and theoretical calculations was demonstrated. It was found that when the geometric dimensions of the rectangular aperture exceed two wavelengths, a traveling-wave regime is established in the waveguide section. Experimentally, it was found that the amplitude distribution of the field for both apertures in the far-field region coincides with the Gaussian distribution down to –8.7 dB. It was shown that the use of rectangular apertures to illuminate the flat face of an axicon with a wave beam is impractical.

Estimation of the Gamma Exposer Rate Constant for Clinically Relevant Radionuclides in Nuclear Medicine Using GATE/GEANT4 Monte Carlo Simulation

Abdulkhaleq O. Jaralah — 2026-06-10

Purpose. To establish a reliable computational method for calculating external radiation dose rates from nuclear medicine patients using Monte Carlo simulation and to systematically evaluate the effects of phantom geometry and detector characteristics on occupational exposure. Methods: MC GATE simulations version 9.1 (Geant4 10.7) calculated external dose rate constants for most clinical radionuclides: ^99mTc, ⁶⁷Ga, ¹⁸F, ¹¹C, ¹³¹I, and ¹²³I. Two phantoms were used, one with dimensions of (25×15×20, 30×20×25, and 35×25×30 cm³), and the other with a fixed length of 170 cm and variable width (15×20, 20×25, and 25×30 cm³), specific to the ^99mTc nuclide. Detector sizes (3×3×3 to 10×10×10 cm³) were evaluated at distances of 1, 2, and 3 m. Different detector media (air, argon, and neon) were assessed for photon sensitivity. The results were compared with experimental data. Results: Simulated results agreed with experimental data within ±10%. Argon demonstrated superior sensitivity compared with air and neon detector media. Phantom dimensions increased overall, resulting in a 36.8% reduction due to self-attenuation. Radionuclides of ¹⁸F and ¹¹C, followed by ⁶⁷Ga, ¹³¹I, ¹²³I, and ^99mTc, posed the highest occupational exposure hazard. Patient body thickness was a more significant attenuation factor than patient height. Conclusion: GATE/Geant4 simulations provide a reliable and accurate tool for evaluating external dose rates in nuclear medicine departments. These findings underscore the importance of using appropriate detector sizes and media, as well as realistic patient geometry, in occupational dose assessments and provide essential data to improve radiation protection protocols.

Radiobiological Effects for Prostate Cancer High-Dose-Rate Brachytherapy

Alaa A. Abou Khadra — 2026-06-10

Background: HDR brachytherapy represents a cornerstone in prostate cancer management by enabling high tumor doses while sparing surrounding normal tissues. Radiobiological modelling allows quantitative assessment of tumour control and normal tissue complication probability for optimization of fractionation schedules. Objective: The purpose of this study is to comparatively appraise the radiobiological outcome of two HDR brachytherapy regimens, 13.5 Gy × 2 fractions versus 15 Gy × 1 fraction, regarding tumor control probability, normal tissue complication probability, and dose-effect metrics in patients presenting with intermediate- to high-risk prostate cancer. Materials and Methods: A retrospective analysis of 20 patients treated by Co-60 HDR brachytherapy was performed. The treatment planning was image-based, in which, target and organ-at-risk delineation was followed standard guidelines. BED, EQD2, and Deff were computed using the linear-quadratic model. TCP and NTCP modeling utilized Poisson-based and Lyman–Kutcher–Burman methods, respectively. Correlations between radiobiological parameters and TCP/NTCP were analyzed. Results: The single 15 Gy fraction regimen resulted in significantly higher BED, EQD2, Deff, and modeled TCP compared with 13.5 Gy×2 fractions (p ≤ 0.031). However, NTCP for urethra at 10% volume was higher in the 15 Gy group (8.42% ± 1.58 vs. 6.86% ± 1.24; p = 0.006). Strong positive correlations were observed between BED, EQD2, Deff and TCP (ρ = 0.984–1.000; p < 0.001). NTCP at 30% urethral volume negatively correlated with BED, EQD2, and Deff (ρ ≈ -0.52; p = 0.003). Conclusions: Higher radiobiological doses (BED, EQD2, Deff) in prostate HDR brachytherapy are strongly associated with improved tumor control, with Deff showing perfect correlation with TCP. A single 15 Gy fraction yields greater radiobiological effectiveness than 13.5 Gy × 2. Urethral toxicity shows no clear correlation at 10% volume but a strong negative correlation at 30%, indicating that higher doses may reduce toxicity at this level. Radiobiological modeling is thus valuable for optimizing HDR planning, enhancing tumor control prediction, and balancing urethral toxicity.

Statistically Conditioned MRI Denoising via Film-Modulated Residual Attention U-Net

D.G. Sliusarenko — 2026-06-10

The quality of MRI images is often limited by spatially inhomogeneous noise, which negatively affects the accuracy of clinical interpretation and automatic analysis. Traditional deep learning methods often implicitly account for noise, leading to excessive smoothing and the loss of fine anatomical structures. In this paper, we propose an Enhanced Denoising U-Net architecture that employs a Feature-wise Linear Modulation (FiLM) mechanism to dynamically adapt to the noise profile of each slice. The model combines a vector of 8 statistical descriptors (including intensity, texture, and frequency characteristics), enabling dynamic control of the network’s internal representations based on specific scanning conditions. To improve physical correctness, training was performed on data with synthetically generated k-space noise. The architecture is enhanced with residual blocks, attention mechanisms, and a multiscale processing module. On synthetic data, the average Peak Signal-to-Noise Ratio (PSNR) improvement was ≈ 20.7 dB, and with an average Structural Similarity Index (SSIM) improvement of approximately 0.73, indicating a deep restoration of structural information. In clinical images, an increase in SNR and stabilization of the coefficient of variation (CV) were observed, confirming the method's physical correctness. Clinical validation on complex contoured structures (hippocampus, brainstem, optic chiasm) showed an increase in the Dice coefficient (DSC) by 0.07–0.12 and a decrease in the HD95 error by 30–50%. The proposed method enables a transition from universal denoising strategies to adaptive reconstruction, ensuring high accuracy of preserving anatomical boundaries. This makes it a promising tool for MRI processing in neuroimaging tasks and variable therapy planning.

Spectroscopic Study of the Interactions of Metal Ions and Proteins with Benzanthrone Derivatives

E. Romanovska-Dzalbe — 2026-06-10

The present work describes the characterization of complexes between various metals and three benzanthrone derivatives bearing structurally similar substituents. Within this investigation, the obtained complexes were meticulously examined using spectroscopic techniques. The absorption spectra of solutions of the obtained complexes in the UV-visible region showed a small bathochromic or hypsochromic shift in the visible region compared to the initial compounds. In the emission spectra of these complexes, significant changes in the positions and intensities of the fluorescence bands were observed as a function of the dyes' chemical structures. Interaction with metal ions in the presence of β-lactoglobulin amyloid fibrils showed metal-specific effects, including fluorescence enhancement with Zn²⁺ and pronounced quenching with Cu²⁺, suggesting a combined contribution of dye–metal and fibril–metal interactions. These findings highlight the potential of benzanthrone derivatives, both free and fibril-bound, as sensitive and selective fluorescent probes for heavy metal detection, providing a foundation for the development of hybrid biomaterial-based sensing platforms.

A Molecular Docking Study of Amyloid-Polysaccharide Composites: II. Interactions with Biologically Active Proteins and Polyphenols

V. Trusova — 2026-06-10

Amyloid fibrils, structurally unique protein aggregates, are increasingly emerging as a novel type of proteinaceous nanomaterial with an expanding range of applications. One example of a biomedical application of amyloid-based nanomaterials is the fabrication of biocompatible hydrogel adhesives for wound healing. The present study was undertaken to evaluate the possibility of utilizing the lysozyme amyloid fibrils integrated with polysaccharide chitosan as a polymeric matrix for incorporation the agents with pronounced wound healing capabilities such as polyphenols and biologically active proteins lactoferrin and conalbumin. Using the molecular docking technique the binding affinities, amino acid composition of the binding sites and possible competitive interactions between polyphenols have been characterized in the two-, three- and four-component systems. Polyphenolic compounds were found to display an ability to associate with bioactive proteins, with the highest binding affinities being revealed for curcumin enol, quercetin and sesamin. In the three- and four-component systems the binding sites for polyphenols are either localized exclusively on lactoferrin or conalbumin or encompass amino acid residues of both fibrillar lysozyme and bioactive proteins. Combinations of polyphenols that can compete with each other for binding sites have been identified. These findings provide a basis for the development of novel amyloid-based nanoformulations with wound-healing properties.

Physics-Informed Neural Network Modeling of Nonlocal Crowd Dynamics for Evacuation Scenarios

A. Naumovets — 2026-06-10

We investigate a nonlocal continuum model of crowd dynamics using a physics-informed neural network approach. The crowd is described by a system of nonlinear conservation laws in which the flux incorporates advection, diffusion, and nonlocal interaction terms accounting for density-dependent motion and limited perception of surrounding agents. Nonlocal effects are modeled through spatial convolutions with smooth kernels, enabling agents to respond to averaged density gradients rather than purely local information. The governing system of partial differential equations is solved using a physics-informed neural network known as PINN, which approximates the solution over the entire space–time domain while enforcing the physical constraints through automatic differentiation. The nonlocal interaction terms are implemented in a stable discrete convolution form, ensuring numerical robustness during training. The approach is demonstrated on the interaction of two pedestrian groups moving in opposite directions in a one-dimensional corridor. The results exhibit the formation and propagation of density fronts, the gradual merging of flows, and the emergence of stable mixed zones. A characteristic feature of the solution is the partial interpenetration of the groups without rigid collisions, reflecting realistic collective motion. To validate the method, the PINN solution is compared with a reference finite-difference scheme based on a Rusanov flux. Qualitative agreement is observed in front structure and mixing dynamics, while quantitative deviations in key characteristics remain
within a few percent. A systematic parameter study shows that the PINN-based solution remains stable under variations of advection velocity, diffusion coefficient, and nonlocal interaction radius, in contrast to the finite-difference scheme, which exhibits strong stability limitations. These results demonstrate that PINN provides a robust and physically consistent tool for modeling nonlinear nonlocal crowd dynamics.

The Theory of the Ideal Armor Plate. Energy Regularities of the High-Speed Body Impact on an Armor Plate

M.P. Odeychuk — 2026-06-10

This study analyzes the optimal energy characteristics of a flying body (FB) impacting an armor plate (AP). The considered energy characteristics include momentum, kinetic energy, and the power of both bodies. It is shown that only a small fraction of the FB momentum is transferred to the AP, whereas nearly all of the FB kinetic energy is converted into the internal energy of the AP. This internal energy consists of the energy of mechanical oscillations of the plate and the energy associated with material displacement within it. The energy of the natural oscillations of the AP, modeled as a rectangular parallelepiped with dimensions a, b, (with a ⁓ b) and thickness c, is estimated. The frequencies of bending oscillations perpendicular to and along the plate surface are calculated. It is shown that the energy of bending oscillations along the surface with the largest area exceeds that of oscillations perpendicular to the surface by a factor of a²/c². The transfer of the FB kinetic energy is assumed to occur in a cylindrical channel of base area S₀. It is shown that the maximum power transferred from the FB to the AP is equal to 16/27 ≈ 0.5926 of the initial FB power and is accompanied by a reduction of the FB velocity by a factor of three. The characteristic penetration length corresponding to maximum power loss is proportional to the FB length h. The multilayer AP configuration is also considered. It is shown that in subsequent layers with lower material density, conditions for maximum power loss are preserved. The thickness of each layer is determined by the distance over which maximum power loss occurs. The results indicate that properly designed multilayer APs can significantly reduce overall dimensions and weight while maintaining high protective efficiency. It should be noted that the present analysis is qualitative and does not aim at quantitative agreement with experimental data, as some secondary effects are neglected. The results provide a physical basis for understanding energy dissipation mechanisms and suggest directions for further optimization using numerical methods.

Axially Symmetric Sharma Mittal Holographic Dark Energy in the Brans- Dicke Theory

Suresh Kadali — 2026-06-10

This study investigates Sharma–Mittal Holographic Dark Energy (SMHDE) within the context of Brans–Dicke theory of gravitation in an Axially Symmetric Cosmological Model. By employing Sharma–Mittal entropy, which provides a unifying generalization of Tsallis and Renyi entropies, a modified form of holographic dark energy density is formulated to incorporate non-extensive thermodynamic effects. The corresponding field equations are derived and solved to obtain exact analytical solutions. Furthermore, key cosmological parameters such as the EoS parameter, deceleration parameter, and squared speed of sound are systematically analyzed to examine the dynamical behaviour and stability of the model. The results indicate that the proposed framework successfully describes the late-time accelerated expansion of the cosmos while also accommodating possible anisotropies in the early cosmos. Overall, the model presents a consistent and physically viable extension of conventional holographic dark energy scenarios within scalar–tensor gravitational theory.

Epitaxial Stabilization and Radiation-Stimulated Segregation in CA-PVD AlN/CrN Multilayer Coatings Under Ion Bombardment

O.V. Maksakova — 2026-06-10

This paper investigates the regularities governing the formation of the atomic-crystalline architecture, surface topography, and chemical composition of AlN/CrN multilayer coatings deposited via cathodic arc physical vapor deposition onto AISI 321 austenitic stainless-steel substrates. The synergistic effect of the negative substrate bias voltage (–50, –100, and –200 V) and the deposition duration of individual AlN layers (10, 40, and 60 s) on the kinetics of phase competition and the evolution of radiation-stimulated nanostructures was analyzed. Using X-ray diffraction and scanning electron microscopy, combined with energy-dispersive X-ray spectroscopy, it was established that at low deposition energies (–50 V, 10 s), the epitaxial template effect of the c-CrN matrix dominates, thereby stabilizing the metastable cubic c-AlN phase. Increasing both the layer thickness and the substrate bias to –100 V leads to the breakdown of pseudomorphic growth and transitions the system into a possible nanocrystalline or quasi-amorphous state. At high bias potential of ‑200 V, complete thermal relaxation occurs, accompanied by a textured phase transition of AlN into its stable hexagonal wurtzite modification (h-AlN). A counterintuitive decrease in the aluminum concentration (from 46.88 to 33.72 at. %) despite the prolonged growth time was observed. This phenomenon is driven by the selective re-sputtering of lighter Al atoms under the influence of a high-energy ion flux. Furthermore, radiation-stimulated interdiffusion of iron from the substrate into the coating, along with an ion-cleaning effect that removes interstitial carbon impurities from the matrix, was recorded. The insights obtained expand current understanding of non-equilibrium solid-state thermodynamics and open new possibilities for the precision tailoring of nanostructured protective coatings by optimizing ion-plasma parameters.