Applied Physics A最新文献

This study analyzes the effect of codoping on the structural and optical properties of ZnO thin films, fabricated using a low-cost, scalable spray pyrolysis method. The XRD analysis revealed that both pure and doped ZnO thin films exhibited a nanocrystalline structure with a predominant zincite phase. The doping process did not significantly alter the crystalline phase of ZnO but reduced both the degree of crystallinity and crystallite size of the thin films. The optical characterization was conducted through ultraviolet (UV)- visible (VIS) spectroscopy to assess how doping with various elements modulates the optical behavior of ZnO thin films across the UV and VIS ranges. The results indicate that doped ZnO films exhibited a high integrated transmittance of over 80% across the visible region. By adjusting the codoping ratio, we obtained a highly crystalline and transparent films with a wide bandgap. This tailoring may enhance the functionality of these thin films in optoelectronic applications specifically solar cells.

This work examines the adjustment of the electron beam deflection angle in scanning electron microscopy (SEM) to improve the precision of microstructural characterisation, especially for sustainable energy materials. constructing and tested three magnetic objective lens designs (m1, m2, and m3) using finite element method simulations, magnetic flux density profiling, and beam-trajectory calculations. Model m1 stood out from the others because it had the smallest probe diameter, less spherical and chromatic aberration, and a longer working distance of 6.287 mm. The best deflection angle was found to be between 0.1 and 0.2 mrad, and 0.15 mrad always gave the finest focus at all accelerating voltages. Model m3 had the maximum magnetic flux density, but its bigger aberration coefficients made the picture quality worse. These results make it clear how important balanced magnetic field distribution and lens shape are to SEM performance. The improved arrangement described here offers a more dependable imaging approach for nanostructured materials used in photovoltaics, batteries, and thin-film energy devices.

In this study, the effect of static charge at the interfacial layer of MOS devices is investigated employing Al₂O₃ dielectric thin film on two different grades of silicon wafers. The presence of the positive static charge caused the inversion capacitance at high frequency and widening of the hysteresis width. Surface passivation methods including the insertion of SiO₂ buffer layer and post metallization annealing (PMA) successfully passivated the electrical defect states, whereas the static charge remained after passivation. High leakage current density was measured for the devices with static charge, which indicates that the leakage current density is attributed to the presence of static charge. To understand this phenomenon, the conduction mechanism of observed I-V curve was analyzed. The device with Al₂O₃/Si and Al₂O₃/SiO₂/Si structure followed the Poole-Frenkel (PF) emission and energy level of trap states ((:{{Phi:}}_{T})) was calculated. For the devices with Al₂O₃/Si structure, the trap energy level was calculated to be 0.244 eV for the sample without static charge and 0.255 eV for the sample with static charge. After inserting the buffer layer, the trap energy level was calculated to be 0.47 eV and 0.52 eV respectively. After PMA, the device with Al₂O₃/SiO₂/Si structure followed the Fowler-Nordheim (FN) tunneling mechanism and barrier height ((:{{Phi:}}_{b})) was calculated to be 1.17 eV for the sample without static charge and 0.95 eV for the sample with static charge. Through these results, it is expected that the static charge induces the band bending of the insulating layer, resulting in the increase of leakage current density.

Charge-conduction mechanisms in the Pd/n-Si Schottky diode were investigated using current-voltage (I-V) measurements over a temperature range of 20–360 K. Variation in diode parameters with temperature indicates that silicon (Si) exhibits two distinct conduction mechanisms, with their relative dominance depending on temperature. At low temperatures, diode conduction is dominated by thermionic field emission, while at high temperatures, it is dominated by thermionic emission. At low temperatures, diode parameters exhibit strong temperature dependence, whereas at high temperatures they show little or no temperature dependence. These results are crucial to investigations aimed at enhancing the electrical properties of silicon-fabricated detectors, as they address challenges caused by charge freeze-out at low temperatures, high leakage currents, and barrier height instability at higher temperatures, which affect diode sensitivity and performance. As a result of this work, the temperature range for the desired diode properties would be identified and optimised, while minimising the range for undesired properties.

In this study, molecular dynamics (MD) simulations were employed to conduct tensile tests on twinned Cu-Ag alloys with varying twin boundary (TB) parameters (spacing: 1.22–6.10 nm; orientation: 0°-360°) and grain boundary affected zone (GBAZ) segregation features. The deformation history, stress-strain response, and microstructural evolution throughout the tensile process were systematically analyzed. By integrating common neighbor analysis (CNA) and dislocation structure characterization, the regulatory effects of TB parameters and GBAZ segregation on the alloy’s mechanical behavior were elucidated. Results show that smaller TB spacing (e.g., 1.22 nm) elevates the alloy’s stress level, while TB orientation exerts a periodic effect on the maximum stress—peaking at 0° and 90° (2.7 MPa) and reaching minima at 45° and 135°. Subsequently, the MD simulation data were processed into a normalized structured dataset. Machine learning (ML) techniques were then applied: regression models (Random Forest, Linear Regression, Extra Trees, CatBoost) were trained on this dataset to predict the alloy’s mechanical properties, and a stacked ensemble framework was established to enhance the prediction accuracy. Among single models, Extra Trees performed best—achieving R²=0.604, RMSE = 0.104 for flow stress prediction and R²=0.662, RMSE = 0.072 for maximum stress prediction—exhibiting high accuracy especially in the elastic stage (ε < 5%). This study provides a theoretical basis for the microstructural optimization and mechanical property prediction of twinned Cu-Ag alloys, and the proposed method exhibits extensibility to other nanostructured alloy systems.

The magnetic properties of the iron selenite compound (Bi_{25}FeO_{40}) were studied using the mean field approximation based on the Gibbs-Bogoliubov inequality. To do this, we presented the phase diagram in the ground state of the system, revealing the existence of several stable ferromagnetic ordered phases depending on the values of anisotropy and external magnetic field. We also studied the effect of different physical parameters on the thermal variation of magnetisation, magnetic susceptibility and the hysteresis behaviour of the system. Phase diagrams at finite temperature were also presented. The results show that the saturation value in the ground state, the critical temperature and the blocking temperature (in the presence of an external magnetic field) are sensitive to variations in physical parameters. We also revealed the existence of first-order phase transitions between ordered phases, as well as second-order transitions between ordered and disordered phases. Finally, we showed that, for certain values of the physical parameters, the system exhibits multiple-loop hysteresis behaviour, and that the area of the central loop varies as a function of these parameters. Finally, our study fills a gap in the literature: to our knowledge, no previous work, such as by Monte Carlo simulations, had systematically mapped the phase diagrams (ground state and finite temperature) or studied the effects of physical parameters on the magnetic properties and hysteresis behaviour of (Bi_{25}FeO_{40}). This will be useful as a reference for future numerical and experimental studies.

In this work, we develop and characterise isotropic magnetorheological elastomers (MREs) composed of evenly distributed flake-shaped electrolytic iron particles (EIPs) within a silicone elastomer matrix. The study examines how temperature, magnetic field strength, and particle shape influence the stress relaxation and magneto-mechanical behaviour of MREs. Experimental results demonstrate that incorporating flake-shaped EIPs substantially enhances the magneto-responsive properties of the MREs. Compared to spherical particles, flake-shaped particles offer better interfacial interactions and mechanical reinforcement, and the formation of internal particle chains under applied magnetic fields increases the storage modulus. Research on stress relaxation indicates that magnetic fields slow down the stress decay rate and extend relaxation times, suggesting enhanced energy retention. At higher temperatures, temperature-dependent studies reveal a decrease in the magneto-field modulus (MFM) and accelerated stress relaxation, due to increased polymer chain mobility and the reorientation of magnetic particles. These findings demonstrate the opposing effects of thermally induced softening and magnetic-field-induced stiffening. This work supports the application of flake-based MREs in adaptive systems, including soft robotics, actuators, and vibration-damping devices across various thermal environments. It provides valuable insights into the temperature-sensitive viscoelastic response of these materials.

A novel KMnO₄-coordinated L-arginine complex was synthesized and comprehensively investigated through an interdisciplinary approach encompassing crystal-growth modeling, theoretical calculations, spectroscopic characterization, and nonlinear optical (NLO) analysis. Incorporation of KMnO₄ into the L-arginine matrix induces pronounced lattice distortion, manifested by anisotropic crystal growth along the a-, b-, and particularly the c-axes. XRD reveals an orthorhombic structure with a nearly distorted P2₁/c space group, sharp diffraction peaks, and high crystallinity. Vibrational modes analyses confirm non-centrosymmetric geometry and active functional modes; fundamental requirements for NLO activity. Theoretical calculations involving geometry optimization, Mulliken charge distribution, and molecular electrostatic potential (MEP) mapping indicate extensive charge redistribution and strong metal–ligand field interactions. Optical studies disclose a direct band gap of 3.67 eV, high birefringence (Δn = 0.20), and 1.86 (2.85 mm) optical transmittance, establishing the complex as a wide-band-gap material resistant to visible-region carrier absorption, suitable for UV-active and high-power photonic applications. The measured third-order nonlinear optical susceptibility (χ³ = 4.82 × 10⁻⁷ esu) demonstrates a strong third-order response arising from efficient intramolecular charge transfer within the Mn–O–C–N coordination framework. Correspondingly, the nonlinear refractive index (n₂ = 1.35 × 10⁻⁸ cm² W⁻¹) is attributed to electronic cloud distortion and localized defect-state interactions, yielding pronounced self-focusing behavior. The nonlinear absorption coefficient (β = 5.47 × 10⁻⁵ cm W⁻¹) signifies reverse-saturable absorption (RSA) driven by excited-state processes, advantageous for optical-limiting and photonic-switching functions. HOMO–LUMO transitions (H → L ≈ 0.625 eV) and electronic spectra support effective ligand-to-metal charge transfer and band-gap modulation, while NBO and perturbation analyses reveal intramolecular charge delocalization. Collectively, these results affirm that KMnO₄-doped L-arginine crystal combines broad optical transparency with pronounced third-order nonlinearity, establishing it as a promising candidate for next-generation photonic and optoelectronic devices.

Smart textiles, along with flexible electronics and wearable technologies, have become integral to modern life, including healthcare and defense. The increasing demand for these innovations has emphasized the need for scalable, efficient, and reproducible manufacturing techniques. In response to this demand, a novel atmospheric pressure plasma jet (APPJ) technique has been developed to deposit various nanomaterials, including carbon nanotubes, graphene nanoplatelets, polyaniline, and iron chloride, onto flexible and delicate substrates such as paper and fabric. This cost-effective, single-step method offers significant advantages over conventional approaches by eliminating the need for post-processing while maintaining excellent compatibility with flexible surfaces. Plasma-deposited nanomaterials were compared with other samples deposited under similar gas flow and other experimental conditions. The results revealed higher density and superior conductivity of the plasma-treated coatings, with a sheet resistance of 3.32 kΩ/sq over a 1 cm² area. In contrast, non-plasma-coated samples demonstrated a sheet resistance range of several hundreds of kΩ/sq for the same area. Furthermore, the plasma-coated fibers showed remarkable durability in non-ionic detergent solutions, confirming their potential in real-life applications. This advanced plasma-assisted deposition method can revolutionize the fabrication of conductive textiles, wearable electronics, sensors, supercapacitors, and other emerging technologies, providing a versatile platform for integrating electrical functionality into the next generation of flexible devices.

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