Nanotechnology最新文献

Self-powered solar-blind photodetector offers irreplaceable advantages for applications such as wearable electronics and ultra-low power systems, but their performance is often limited due to the absence of an external bias. In this work, we demonstrate a high-performance self-powered photodetector based on a well-designed NiO/Ga₂O₃ p-i-n heterostructure that requires no complex pre-treatment methods. The photodetector exhibits a high photo-to-dark current ratio of 378, a high responsivity of 137 mA W^-1, and fast response times of 27 ms/650 ms. Furthermore, we quantitatively elucidated the physical origin of the self-powered behavior. The analysis of the p⁺-n^-one-sided abrupt junction, based on repeatable capacitance-voltage characterization, confirmed the presence of a strong built-in electric field with a calculated maximum field strength of 136 kV cm^-1. It is the fundamental driving force for the photodetector's excellent self-powered performance.

The efficiency of green hydrogen production via water splitting is typically hindered by the sluggish kinetics of the oxygen evolution reaction (OER). Here we investigate the performance of various nickel nanoclusters, deposited via a binder-free gas-phase method, as OER catalysts on two distinct porous platforms: commercial gas diffusion layers (GDLs) for electrocatalysis and mesoporousTiO2thin films for photoelectrocatalysis. For dark electrocatalysis on GDL, we find a non-linear relationship between catalyst loading and activity, where the lowest Ni loadings exhibited the highest specific activity. Trace iron impurities in the electrolyte dramatically enhanced the performance, leading to a 120-fold increase in specific current for the lowest loading samples through thein situformation of highly active NiFe oxyhydroxide species. When integrated as co-catalysts on mesoporous TiO_₂photoanodes, Ni nanoclusters significantly improved photocurrents, with an optimal loading of 0.27-0.89μg cm^-2. While Fe impurities also boosted photoelectrochemical performance at low Ni coverages, the effect was less pronounced and became detrimental at higher loadings. These findings underscore that the precise control of the catalyst loading and composition is decisive for designing scalable and highly efficient systems for water oxidation.

Electron beam-induced current (EBIC) is a vital characterization technique for promising semiconducting single-walled carbon nanotube (CNT) devices, yet its underlying imaging mechanism remains poorly understood. This study elucidates the EBIC imaging mechanism in CNTs. By simultaneously analyzing secondary electron (SE) and EBIC signals at landing energies of 1 keV and 10 keV in scanning electron microscopy (SEM), it is demonstrated that the EBIC signal is strongly correlated with SE emission intensity. This finding indicates that, unlike traditional three-dimensional semiconductor materials where EBIC imaging is dominated by built-in potential, the Pd-CNT system is governed by substrate charging polarity and electron dose. Moreover, the signal intensity distribution is determined by the resistance gradient along the CNT. This fundamental clarification of the physical origin of EBIC in CNTs provides the essential mechanistic foundation required for the reliable quantitative analysis of electrical properties at nanoscale interfaces in low-dimensional electronics.

This study investigates the damage mechanisms induced by HPM stress in GaN HEMTs using Sentaurus TCAD numerical simulations and proposes corresponding multi-scale protection strategies. A comprehensive simulation model of a depletionmode GaN HEMT was established. The analysis of the evolution of internal electric field, current density, and temperature profiles under HPM stress reveals that the failure mechanism is primarily attributed to an electro-thermal positive feedback loop between the gate and source, leading to thermal accumulation and eventual thermal breakdown when the lattice temperature reaches the melting point of GaN. Based on this understanding, protection strategies were developed through structural optimization. The results demonstrate that moderately increasing the gate length (0.25-0.3 μm), extending the field plate length (1.85-2.25 μm), and optimizing the channel layer thickness (0.4-0.6 μm) effectively reduce the internal electric field and current density, thereby mitigating thermal accumulation and enhancing HPM resilience without significantly compromising DC performance.

A nano-inscribing technique was tested as a method of cost-effective replication of blazed diffraction gratings for x-rays. A saw-tooth mold for the nano-inscribing was fabricated by a double-replication process from a master blazed grating. The nano-inscribing was performed using a UV-curable resist of low viscosity to provide a small thickness of the resist replicas, required for a following transfer process. The nano-inscribing process was optimized to minimize surface relaxation and preserve the saw-tooth shape of the grooves, required for high diffraction efficiency. The quality of the replica gratings was evaluated via diffraction efficiency simulations. The simulations demonstrated that near theoretical efficiency can be achieved for the x-ray gratings made by the nano-inscribing approach.

Metal-organic frameworks (MOFs) have emerged as promising microwave absorbers owing to their tunable composition, structural diversity, and high porosity. However, their low intrinsic permittivity leads to impedance mismatch and inadequate attenuation capacity. To address this limitation, we developed a series of polypyrrole (PPy)/MOFs composites through ultrasonic integration of high-permittivity PPy nanoparticles with hydrothermally synthesized [(CH₃)₂NH₂]Mn(HCOO)₃(Mn-MOF). The optimal composite with a PPy-Mn mass ratio of 4:1 (50 wt% filler in paraffin) achieved a minimum reflection loss (RL) of -63.4 dB at 17.67 GHz with an ultrathin thickness of 1.7 mm. Its maximum effective absorption bandwidth (EAB, RL⩽ -10 dB) reached 5.44 GHz (10.60-16.04 GHz) at a thickness of 2.2 mm. Unlike typical PPy-based absorbers limited to medium frequencies and greater thicknesses, this work achieves the integration of strong absorption, high-frequency, and an ultrathin profile (~2 mm). Enhanced performance stemmed from synergistic interfacial polarization, dipole relaxation, and optimized impedance matching. This study presented an effective strategy to design MOF-based as the promising microwave absorber.

The static and dynamic properties of meron-like magnetic textures stabilised by anisotropic Dzyaloshinskii-Moriya interaction (A-DMI) are examined in nanodots across hosting geometries. By considering a circular magnetic nanoring, we use micromagnetic simulations to identify geometric conditions that minimise the total energy and favour the stabilisation of vortex or antivortex textures as a function of the ring hole. For each texture, we find an optimal geometry that maximises stability. We further map the spin-wave spectra under in-plane and out-of-plane field pulses. For antivortices, out-of-plane excitation yields a single well-defined mode, whereas vortices exhibit a richer modal structure arising from the competition between A-DMI and geometry. Under in-plane excitation, vortices and antivortices support the same number of low-frequency modes with similar spatial profiles. These results highlight the interplay between meron cores and chiral interactions, with implications for spintronic and magnonic devices that rely on stabilising magnetic textures or tailoring spin-wave modes.

A number of ecological stressors negatively impact on rice yield, drastically lowering crop productivity. Among these, arsenic stress is considered a major abiotic factor that affects number of processes in plants, ultimately leading to reduced productivity. Nano-hormonal interactions have garnered allure as a possible way to lessen arsenic toxicity in plants. In this work, the synergistic effects of zinc oxide nanoparticles (ZnO-NPs) and epibrassinolide (EBL) on rice (Oryza sativa) with arsenic stress were examined. A fully randomized block design (CRD) was used in a pot experiment. Exposure to arsenic (150μm) impaired growth (length and biomass), photosynthetic performance, soluble sugars, starch, and sucrose (primary metabolites), phenolics and flavonoids (secondary metabolites), as well as key mineral nutrients. However, foliar application of ZnO-NPs (100 mg l^-1) and EBL (0.01μm) alleviated arsenic-induced toxicity by promoting enzymes activity and promoting the involvement of secondary metabolites in defense. These improvements in the biochemical and physiological matrices of rice plants effectively mitigated growth losses under arsenic stress. Overall, this work concludes the interactions between ZnO-NPs and EBL in modulating development and growth in rice, thereby contributing to global food security.

Atomic switch (AS) devices are potential candidates as selector devices in cross-point array memory architecture. In this study, we improved the switching characteristics of an AS device by severely restricting Ag doping into the HfO2 electrolyte. Using a collimated sputtering process, we precisely controlled the amount of Ag doped in the electrolyte, which resulted in a higher threshold voltage (Vth) and enhanced turn-off speed compared with conventional AS devices. To understand the origin of these improvements, we analyzed both Ag-doped AS device and a conventional AS device with the framework of field-induced nucleation theory. Both devices showed an exponential relationship between delay time and voltage, but with different values of nucleation barrier energies (W0); the Ag-doped AS device exhibited a significantly higher W0. These results indicate that limit restricting Ag doping increases the nucleation barrier energy, leading to less stable filaments and thereby improving switching characteristics.

Metal halide perovskites generally present functional properties such as ferroelectricity and ferroelasticity, forming nano domains which dictate most of their physical properties. Crystalline changes in the nanoscale, including heat-induced domain rearrangements, are generally responsible for the appearance of structural defects. This is valid for bulk and surface but is especially relevant in nanomaterials, where charge traps lead to degradation in perovskites, reducing the lifetime and compromising their use in solar cells. The growth of oriented nano domains, on the other hand, does not only improve perovskite-based solar cells efficiency and lifetime, but can be potentially used to tailor conductivity and optical emission, opening new possibilities for applications in optoelectronic devices. Studying phase transitions, defect formation and nano domain dynamics in perovskites is challenging, requiring techniques capable of probing crystals with high strain sensitivity and good spatial resolution.In situandoperandoexperiments, for instance, are difficult to perform using traditional techniques which require severe sample preparation. Recent developments in synchrotron x-ray sources, with the emergence of instruments able to offer small x-ray beams with improved photon flux and coherence, can bring new insights into the field. This review focuses on x-ray methods for the study of perovskite basic properties, enlightening possible multi-technique experiments which are currently available in large scale facilities.