Physics of the Solid State最新文献

This paper presents a detailed comparative analysis of β-Ga₂O₃-buffered Al_0.25Ga_0.75N/GaN high electron mobility transistors (HEMTs) incorporating two distinct back barrier configurations: In_0.15Ga_0.85N and a unified β-Ga₂O₃ layer. The devices are evaluated under two gate metal work functions (ϕₘ = 4.3  and 5.6  eV) to examine their influence on device performance. DC and RF characteristics, including drain current (I_D), transconductance (gₘ), and unity current gain cutoff frequency ( f_T), are extracted at a drain bias of 20  V. The β-Ga₂O₃ back barrier device demonstrates superior performance, achieving higher peak drain current densities of 6  A/mm (ϕₘ = 4.3  eV) and 5.63  A/mm (ϕₘ = 5.6  eV), compared to 3.9  and 3.6  A/mm, respectively, for the InGaN counterpart. A significant shift in threshold voltage (V_th) is observed with the β‑Ga₂O₃ barrier, indicating enhanced channel control. Moreover, transconductance values exceeded 1  S/mm, and peak f_T values approached 1.45 × 10¹¹  Hz, underscoring the advantages of β-Ga₂O₃ in high‑speed applications. The ON-resistance (R_on) analysis shows that the β-Ga₂O₃ back barrier device achieved a minimum R_on of 0.28 Ω mm (ϕₘ = 4.3  eV), compared to 0.55  Ω mm for the InGaN back barrier. The results establish that both the gate work function and back barrier selection critically impact the electron confinement, threshold behavior, and high-frequency response of GaN-based HEMTs on β-Ga₂O₃ substrates.

Modification of carbon steel surface edges using electro-explosive alloying (EEA) and subsequent treatment with a pulsed electron beam is discussed. The research shows that the combined use of these technologies leads to significant improvements in the material’s performance characteristics, such as microhardness and wear resistance. During the experiments, the optimal electron beam energy density and number of pulses have been determined, making it possible to achieve maximum microhardness values exceeding those of the uncoated steel. Changes in the surface structure, including the formation of microcracks and dendritic crystallization, are also analyzed. The results show that the proper selection of processing parameters improves the physicochemical properties of the steel, making this technology promising for use in various industries.

The absorption and luminescence spectra of InSe and GaSe nanoparticles and InSe/GaSe and GaSe/InSe nanoheterostructures based on them synthesized by laser ablation in a liquid are studied experimentally. A pulsed Nd:YAG-laser with built-in generators of the second and third harmonics intended for generation of radiation with wavelengths 1064, 532, and 335 nm is used as the radiation source. The ablation is carried out in a quartz cell with distilled water using the Nd:YAG laser with wavelength λ = 1064 nm, pulse duration 10 ns, pulse energy 135 mJ, and pulse repetition frequency 10 Hz for ~10 min. The energy-gap widths of the InSe and GaSe nanoparticles are calculated by the Tauc method. InSe/GaSe and GaSe/InSe semiconductor/semiconductor nanoheterostructures are shown to form on the base of InSe and GaSe nanoparticles in nanoparticle bulks. The methods of synthesis of semiconductor core/shell nanoparticles in a solution are discussed.

Advances in materials engineering have demonstrated the high stability and low toxicity of tin-based perovskites, presenting an excellent lead-free alternative. Consequently, an ab initio study was conducted to investigate the structural, electronic, and optical properties of the tin-based perovskite oxides ASnO₃ (A = Ba, Ca, Sr, and Mg). These properties were examined using the Quantum Espresso Simulation Package (QE) with the GGA functional. The structural parameters showed highly consistent results with previous experimental and theoretical findings. The electronic calculations for BaSnO₃, CaSnO₃, SrSnO₃, and MgSnO₃ revealed semiconductor characteristics with indirect bandgaps of 3.12, 3.07, 3.2, and 0.95 eV, respectively. The total and partial densities of the states confirmed the localization of electrons within various bands. Analysis of the ASnO₃ optical properties indicated significant absorption behavior and weak reflection performance. Overall, these tin-based perovskite oxides hold outstanding potential as materials for the electronic industry, particularly in optoelectronic applications.

In this study, a series 50V₂O₅–15Bi₂O₃–(35–x)ZnO–xNa₂O, where x takes up the values of 0, 5, 10, 15, and 20 mol % were synthesized using the melt-quench technique. The physical, optical, and structural properties of the glass series was comprehensively studied using a range of characterization techniques. XRD analysis demonstrated amorphous structure of the glass series. The density and related parameters showed a decrease in the material’s compactness and a loosening of the network structure. Fourier-transform infrared (FTIR) spectroscopy provided information on the vibrational modes and bonding characteristics, while Raman spectroscopy further elucidated the vibrational signatures of the glass network. The existence of BiO₃ pyramidal units and BiO₆ octahedral units is confirmed by both Raman and FTIR spectra and presence of VO₄ tetrahedral units and VO₅ trigonal bipyramids in the glass matrix was also identified. Optical properties such as optical energy bandgap, Urbach energy and cut-off wavelength were studied through UV-Vis spectroscopy. With higher Na₂O content, an increase in the optical energy bandgap (1.53–2.09 eV) was observed in the glass series, highlighting the impact of Na₂O variation on the optical performance of the glass system. Metallization criterion (0.28–0.32), optical dielectric constant (7.83–6.29), refractive index (2.97–2.70), dielectric constant (8.83–7.29), linear optical susceptibility (0.62–0.50), χ⁽³⁾ ((0.152–0.063) × 10^–10 emu) and β (24.38–19.87 cm/GW) were also determined. The prepared glass samples may have potential application in non-linear optical devices and photonic systems.

Thickness dependent charge transport mechanism in organic semiconductors has been demonstrated. Material layer thickness of simulated device structures has been considered for different values to verify the trap signatures by introducing different estimation process. A theoretical model has been proposed to form a reliable relationship between thickness dependent trap energy and ideality factor in terms of incremental conductance from which (alpha ) has been calculated for different experimental dye based experimental devices. Investigation reveals significant similarity shown in logarithmic plot of the abovementioned parameters consistent with proposed theoretical model. Using the approximated theoretical observation following the further modification of Space Charge Limited Current equation, thickness dependent charge mobility has been estimated for different layer thickness of OSC device. The obtained result in this context shows good agreement with defined standard value of simulation. Electrical parameters relevant to thickness dependent charge transition process and their variation with device layer thickness has also been extrapolated. It has been observed that trapping states induced charge density decreases at trap filled high voltage regime with increasing layer thickness while subsequently impact of trap energy enhances in this perspective.

We present a dual-band dielectric metamaterial absorber based on Strontium titanate (STO) resonators that exhibits strong thermally tunablility in the microwave regime. The absorber achieves near-unity absorption at two distinct resonance frequencies of 12.18 and 17.51 GHz at 293 K. Both peaks exhibit a noticeable shift toward higher frequencies (blue shift) by approximately 240 and 300 MHz, respectively, as the temperature increases from 293 to 303 K, while maintaining stable absorption intensity. This frequency tunability is achieved by the temperature dependence of STO permittivity, allowing precise control of the resonant frequencies without compromising performance. In addition, the metamaterial absorber exhibits outstanding angular stability. The absorption is maintained above 90% at incident angles up to 60° which is suitable for practical applications with different incident waves. These characteristics emphasize the potential of the STO dielectric metamaterial for advanced thermal sensing devices, tunable filtering, and adaptive electromagnetic wave control.

Transition metal oxide-based composites have emerged as attractive candidates for supercapacitor electrodes due to their excellent redox activity, stability and cost-effectiveness. In this study, cobalt manganese oxide nanostructures were grown on nickel foam using a hydrothermal method and then integrated into the conductive polymer polyaniline (PANI) composite. The hybrid cobalt manganese oxide/polyaniline composite combines the high theoretical capacitance of metal oxides with the superior electrical conductivity of PANI. The structural and morphological properties were characterized using XRD, FTIR, and SEM techniques, while the electrochemical behavior was evaluated through cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements. The composite electrode exhibited a high specific capacitance of 1326 F g^–1 at 0.5 A g^–1, which was attributed to its porous morphology and increased active surface area. These findings demonstrate the potential of CoMn₂O₄/PANI composites as high-performance electrode materials for next-generation energy storage devices, especially in pseudocapacitor applications.

The growing demand for terahertz wave detectors in high-speed wireless communication, real-time security imaging, and food inspection has driven significant interest in silicon-based solutions. Recent advances in Si field-effect transistors and CMOS-compatible Schottky barrier diodes have paved the way for scalable, multi-pixel THz imaging detectors. This work introduces a silicon nano-ring FET architecture by integrating the circular plasmonic confinement with CMOS-compatible fabrication. By employing an asymmetric source-drain configuration and grounding the outer ring source, the proposed design effectively reduces junction leakage and enhances radiation coupling efficiency. A photo response is enhanced 535 times as compared to prior devices with the same asymmetry ratio, whereas the intrinsic resistance limit is reduced from 8 to 0.13 μm. TCAD simulations are performed, which validate the analytical model, showing <25% deviation between the predicted and simulated data. Therefore, the SNR-FET demonstrates an improvement in the performance ratio of 98.5%, sensitivity of 97.3%, responsivity of 95.6%, and conversion efficiency of 94.5%, along with an 8.3% reduction in noise equivalent power as compared to the existing models. The results confirm that the proposed SNR-FET allows room temperature, broadband detection capability of up to 0.2 THz and a pathway toward scalable, low-cost next-generation on-chip THz imaging and sensing systems.

This study emphasized the green synthesis of zinc oxide (ZnO) nanoparticles utilizing the leaf extract of Camphora, which served as a natural reducing agent and stabilizer for the ZnO nanoparticles. The developed ZnO nanoparticles were characterized by several analytical techniques including X-ray diffraction (XRD), Ultraviolet–visible spectroscopy (UV–Visible), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential (ZE), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area analysis, and photoluminescence (PL). The XRD results confirmed that the ZnO nanoparticles were hexagonal wurtzite crystal structure with an average crystallite size of approximately 13 nm. Meanwhile, TEM analysis revealed that the nanoparticles are quasi-spherical in shape with an average diameter of 16 nm, indicating successful nanoparticle formation with a uniform morphology. The UV–Visible analysis showed a strong absorption peak at 334 nm, corresponding to a widened bandgap of 3.7 eV due to quantum confinement. FTIR spectra confirmed the involvement of phytochemicals in nanoparticles formation and stabilization. BET analysis indicated mesoporosity with predominate pore diameter of 35–40 nm, enhancing surface reactivity. Photocatalytic activity was evaluated against methylene blue (MB) dye under sunlight, where the ZnO nanoparticles achieved 97% degradation within 90 min. The high efficiency was attributed to nanoscale dimensions, oxygen vacancies and enhanced generation of reactive oxygen species. Importantly, reusability tests demonstrated sustained performance with 92% efficiency retained after five cycles. These findings highlight Camphora mediated ZnO nanoparticles as eco-friendly, stable and highly efficient photocatalysts for potential applications in wastewater treatment and environmental remediation.