Technobius Physics

Standardized extraction of optical band gap and urbach energy in zno and al-doped zno thin films from uv–vis spectra: an in-silico workflow

Do-Yoon Lee, Gye-Tai Park — Sun, 29 Mar 2026 00:00:00 +0500

This study develops and validates a reproducible computational workflow for extracting the optical band gap and Urbach tail parameters of ZnO and Al-doped ZnO thin films from UV–Vis spectra. Synthetic transmission datasets were generated for ZnO and ZnO:Al (0–3 at.% Al) using a physically consistent thin-film optics model with realistic spectral broadening and noise, followed by standardized post-processing to reconstruct absorption behavior and perform band-edge analysis. The optical band gap values derived from the band-edge region remained tightly clustered across all compositions, with group means near 3.31–3.33 eV and small between-replicate dispersion (standard deviation ≤ 0.005 eV), indicating robust gap extraction under a fixed regression protocol. In contrast, the Urbach energy exhibited substantially higher variability, with group means spanning approximately 37–112 meV and larger scatter, highlighting the greater sensitivity of sub-gap analysis to low-signal regions and fitting-window selection. Overall, the results demonstrate that band-gap estimation is comparatively stable when procedures are standardized, whereas Urbach-tail quantification requires stricter control of noise floor and objective windowing. The proposed workflow provides a transparent baseline for consistent reporting and can be directly transferred to experimental ZnO/AZO datasets; the main limitation is that the present results are derived from synthetic spectra, motivating future validation on measured thin-film optical data.

Dynamic strain-gradient-induced polarization and nonlinear electromechanical coupling in noncentrosymmetric quantum oxide crystals

James Whiteker — Sun, 29 Mar 2026 00:00:00 +0500

This study investigates dynamic strain-gradient-induced polarization and nonlinear electromechanical coupling in a noncentrosymmetric wide-bandgap oxide single crystal. The objective was to experimentally verify enhanced dynamic polarization mechanisms beyond classical flexoelectric descriptions and to correlate the results with continuum-level numerical modeling. High-quality single crystals were structurally verified by X-ray diffraction, followed by dynamic polarization measurements over a frequency range from 10 Hz to 1 MHz. Controlled strain gradients were introduced via three-point bending, and nonlinear susceptibility was extracted using harmonic analysis. Finite-element simulations were performed to reproduce spatial polarization distributions under identical boundary conditions. The polarization amplitude exhibited a low-frequency plateau of approximately 4.8 µC/m² and decreased to 3.48 µC/m² at 1 MHz, indicating dispersive dynamic behavior. Under applied strain gradients up to 3 × 10³ m⁻¹, polarization increased from 4.76 µC/m² to 7.81 µC/m², demonstrating nearly linear scaling with higher-order enhancement at larger gradients. A quadratic nonlinear response was confirmed, with second-harmonic polarization reaching 2.052 µC/m² at 100 kV/m. Temperature variation from 20 K to 400 K produced monotonic damping without phase-transition anomalies. Numerical modeling reproduced experimental amplitudes and revealed pronounced spatial localization of polarization. The results confirm robust dynamic electromechanical coupling exceeding classical continuum expectations and establish strain-gradient-driven polarization as a stable and tunable mechanism in noncentrosymmetric quantum crystals. The investigated material was wurtzite ZnO (P6₃mc) with a direct bandgap of approximately 3.3–3.4 eV at room temperature.

Thermal behavior and Fire resistant properties of Vinyl Ester Resines Modified with Dimethyl Methylphosphonate and Diatomite

Mon, 30 Mar 2026 00:00:00 +0500

The thermal behavior and flame-retardant performance of vinyl ester resins (VER) modified with dimethyl methylphosphonate (DMMP) and diatomite (DE) were investigated. Differential Scanning Calorimetry (DSC) was performed using a NETZSCH DSC 300 Caliris Select instrument (Germany). Measurements were conducted in Concavus aluminum crucibles under a nitrogen atmosphere with a constant flow rate of 40 mL/min. VER was modified using three types of fillers: DE alone, a physical mixture of DMMP and DE, and DMMP immobilized on DE. These modifications resulted in distinct values for glass transition temperature, glass transition range, and heat capacity change (∆Cp). These parameters provide insight into the chain mobility and flame-retardant properties of the materials. The narrow transition range and lowest ∆Cp observed for the immobilized DMMP sample indicate the increase in thermal stability of the material compared to the other samples, which corresponds with the LOI and flammability tests. This includes increased decomposition temperature and enhanced char formation, offering improved protection under real fire conditions. These results demonstrate the effectiveness of modifying VER with immobilized DMMP as a strategy for producing flame-retardant materials and may provide guidance for the development of new fire-safe composites.

Energy transport and interaction dynamics of localized waves in nonlinear dispersive systems

Hakan Ozbay — Mon, 30 Mar 2026 00:00:00 +0500

Energy transport in nonlinear wave systems plays an important role in many physical processes where localized waves transfer energy through dispersive media. The objective of this study was to investigate the mechanisms of energy transport in a nonlinear wave system and to determine how nonlinear interactions influence the propagation and interaction of localized wave packets. Experiments were performed using a nonlinear electrical transmission line designed to generate and propagate controlled wave pulses. Temporal waveforms were measured at multiple positions along the transmission medium to analyze propagation dynamics and wave–wave interactions. In parallel, numerical simulations based on a nonlinear wave equation were conducted to reproduce and interpret the observed behavior. The experimental results demonstrated that localized wave packets propagate with nearly constant velocity and maintain a stable waveform during propagation. The initial pulse amplitude decreased only slightly from approximately 8.2 V to 7.5 V over the measured propagation distance, while the pulse width remained within the range of 42–45 ns. Interaction experiments showed that two wave packets temporarily form a combined structure with a peak amplitude of about 13.4 V during collision, after which the pulses recover their original shapes and continue propagating independently. Analysis of the spatial energy distribution revealed that wave energy remains strongly localized and moves through the system without significant dispersive spreading. Numerical simulations reproduced the experimentally observed propagation velocity, pulse stability, and interaction dynamics. These results confirm that energy transport in nonlinear dispersive media occurs through stable localized wave packets whose structure is maintained by the balance between nonlinear self-interaction and dispersion. The findings provide experimental and numerical evidence of efficient energy transfer mechanisms in nonlinear wave systems and contribute to the understanding of soliton-based energy transport in physical media.

Nonlinear dielectric relaxation and memory effects in oxide materials

Milana Bushina — Mon, 30 Mar 2026 00:00:00 +0500

Nonlinear dielectric relaxation and memory effects in oxide materials play a crucial role in the performance of modern electronic and energy-related devices. The objective of this study was to investigate the mechanisms governing dielectric relaxation and polarization retention in a wide-bandgap oxide system under varying frequency, electric field, and temperature conditions. Polycrystalline oxide samples were synthesized using a solid-state method and characterized using dielectric spectroscopy and polarization measurements. Frequency-dependent permittivity, electric-field-induced nonlinear response, hysteresis behavior, and time-dependent polarization decay were systematically analyzed. The results revealed a strong frequency dependence of dielectric properties, with permittivity decreasing from approximately 1200 at low frequencies to about 450 at high frequencies, accompanied by a broad relaxation peak. The application of electric fields led to a nonlinear decrease in permittivity, indicating polarization saturation effects. Polarization measurements showed distinct hysteresis loops with remnant polarization around 0.12 C/m², confirming the presence of memory effects. Time-dependent analysis demonstrated non-exponential relaxation with partial retention of polarization over extended time scales. Additionally, temperature-dependent measurements indicated thermally activated relaxation processes, as evidenced by an increase in permittivity and a shift of relaxation behavior toward higher frequencies. These findings demonstrate that dielectric response in oxide materials is governed by multiple interacting mechanisms, including dipolar relaxation, interfacial polarization, and charge trapping. The study provides a comprehensive understanding of nonlinear dielectric relaxation and memory effects, which is important for the development of advanced dielectric and energy storage materials.