Nanotechnology最新文献

Large area, vertically aligned one-dimensional, hexagonally patterned materials have been found to be efficient substrates for surface enhanced Raman spectroscopy (SERS). Here in this work, we have developed a facile substrate for SERS performance as vertically grown carbon nanopillars (CNPs) inside the porous hexagonally patterned anodic aluminum oxide (AAO). Nanoporous AAO was grown for the best pore ordering for optimum parameters. CNPs were synthesized in the AAO template inside a thermal chemical vapor deposition reactor. CNPs were exposed to mechanical polishing to remove excess overgrown amorphous carbon, followed by chemical etching. This facile SERS substrate was prepared by depositing Au to form SERS-active hot spots. This CNP-Au hybrid substrate for 30 nm Au deposition shows the uniform sub-10 nm gap between subsequent nanopillars. Based on UV-Vis spectroscopy, the plasmonic resonance of the CNP-Au substrate was observed at a wavelength of approximately 540 nm. Rhodamine (R6G) dye was investigated for its very low concentration up to 10^-9M due to its genotoxic and carcinogenic effects on human life. Thus, a low concentration of R6G analyte is strongly desired for sensitive detection. The electric field enhancement was validated with a 3D FDTD Lumerical simulation for CNP@Au-30 nm substrate for a 10 nm gap. This CNP@Au facile SERS substrate shows potential use for novel large-area electrode systems in next-generation optoelectronics, including photovoltaics, light-emitting diodes, ultralow molecule detection, and solar water splitting.

As CMOS technology scales into the nanoscale regime, ensuring the reliability of digital circuits in radiation-rich environments has become a critical challenge. Standard cell libraries, which are foundational to digital design, are typically characterized using extensive SPICE simulations to capture gate delays as functions of input transition time and load capacitance. However, these libraries do not account for total ionizing dose (TID) effects, which are caused by prolonged exposure to ionizing radiation and introduce oxide-trapped charges and interface states that degrade key transistor parameters, such as threshold voltage and leakage current. This results in significant timing inaccuracies, compromising digital timing closure in mission-critical applications such as aerospace and nuclear electronics. In this work, we propose an efficient, TID-aware standard cell characterization methodology for nanoscale CMOS technologies that generates cell characterization data in standard Liberty format, enabling accurate prediction of timing closure under TID influence without incurring any SPICE simulation overhead. Our approach leverages well-calibrated 32 nm Synopsys^©Sentaurus TCAD simulations and variation-aware analytical timing models to capture TID-induced degradation. These effects are incorporated into cell netlists through adjustments to the BSIM parameters to generate both pre- and post-radiation standard cell libraries. Validated using a set of reference designs, including ISCAS benchmark circuits, the proposed methodology achieves accurate path-level timing predictions under radiation while reducing SPICE simulation effort by approximately 81.25%. By bridging device-level radiation effects with cell-level timing abstraction, this scalable framework offers a practical solution for robust and radiation-resilient digital integrated circuit design in harsh environments.

Semiconductor nanowires have continued to be an important material format for both fundamental science and device research. Recent years have witnessed a fantastic progress on semiconductor nanowires across different material systems, such as II-VI, III-V, III-nitrides, and so on. In this review paper, I would like to focus on some of the recent developments in III-nitride nanowires and their device applications. A specific III-nitride nanowire synthesis technique, molecular beam epitaxy (MBE), which is a highly controllable, scalable, and industrial production compatible material synthesis technique, is focused. Recent understanding about the MBE growth of III-nitride nanowires, including low temperature selective area epitaxy and chamber configuration dependent properties, is discussed. Moreover, recent advances on III-nitride nanowire light-emitting and photodetection devices are discussed. In addition, emerging studies on scandium (Sc) incorporated III-nitride nanowires and devices are discussed. The intention of this review paper is to complement recent reviews in the field of III-nitride nanowire research and provide readers some future perspectives on this intriguing semiconductor material system.

Using the mean-field approximation, a formula for the effective electrical conductivity of a two-dimensional system of randomly arranged conducting sticks with a given orientation distribution was obtained. Both the resistance of the sticks themselves and the resistance of the contacts between them were taken into account. The accuracy in the resulting formula was analyzed. A comparison of the theoretical predictions of mean-field approach with the results of direct electrical conductivity calculations for several model orientation distributions describing systems with crossed sticks demonstrated good agreement. Our study showed that cross-alignment of nanowires should lead to a decrease in the electrical conductivity compared to electrodes with isotropically arranged nanowires. We suppose that the widely used model with zero-width sticks is quite acceptable for systems of cross-aligned nanowires, but overestimates their connectivity in isotropic systems. Thus, the enhancement of the electrical conductivity of conducting films with cross-aligned nanowires may be due to a significant difference in the network topology.

We have conducted a detailed investigation of helium ion beam lithography (HIBL) at its resolution limits by calculating three-dimensional energy deposition within a resist. The resist activation energy, a critical physical parameter, was estimated and used as a substitute for the traditionalz-factor, allowing for a systematic evaluation of interdependent lithography performances. Our calculations demonstrate HIBL's exceptional capabilities, including 2.5 nm resolution (30 kV, PMMA, line-scan), large aspect ratios exceeding 9, a proximity effect range of approximately 10 nm at 100 nm depth, and edge roughness below 1 nm. These findings highlight HIBL's potential for advanced nanofabrication applications. Furthermore, our calculation led to a reliable model for accurate pattern prediction and proximity effect corrections, which was verified by experiment.

Increased emissions of volatile organic compounds (VOCs) are prone to cause health issues like cancer and central nervous system disorders, making the development of efficient VOCs-sensing materials crucial. Monolayerα-AsN, a two-dimensional (2D) V-V binary material with a wrinkled honeycomb structure, features better environmental stability (higher cohesive energy than black phosphorus, BP) and tunable electrical properties (unlike single-target VOC-sensing TMDs). It overcomes flaws of existing 2D sensors (BP's poor stability, TMDs' narrow selectivity) while retaining high surface-to-volume ratio, and shows superior adsorption efficiency and selectivity for alcohol VOCs versus BP and acetone-specialized Janus TMDs. However, its VOCs-sensing performance remains uninvestigated. This study employed density functional theory and nonequilibrium Green's function to systematically investigate the adsorption and sensing behaviors of monolayerα-AsN toward the five VOCs. Electronic localization function analysis confirmed physical adsorption (no chemical bonding) betweenα-AsN and all VOCs. Among the tested VOCs, methanol and ethanol exhibited the highest adsorption energy and density (ethanol slightly higher), with ultra-low detection limits (7.69 × 10^-⁴ p.p.b. for methanol and 4.88 × 10^-⁵ p.p.b. for ethanol). Critically, methanol adsorption reducedα-AsN's current by 30%, while ethanol increased it by 100%. These findings demonstrate that monolayerα-AsN holds great application potential for the selective detection of methanol and ethanol.

This paper proposes substrate nitridation as an effective method to reduce radio-frequency (RF) loss in Si-based GaN epitaxial wafers. By optimizing the process, an amorphous SiN_xlayer was formed, which effectively blocks the downward diffusion of Al atoms and suppresses the formation of a parasitic conductive channel, thereby leading to a significant reduction in RF loss. Four distinct pre-flow conditions were specifically designed to decouple and modulate the properties of the AlN/Si interface. A detailed analysis of the initial dislocation evolution behavior was conducted, comparing the nitridated substrate with conventional pre-deposited Al processes. Although the nitridation process leads to a moderate increase in threading dislocation density by promoting their parallel propagation, the proposed dislocation coalescence mechanism, supported by our experimental design and analysis, indicates that the spatial extent of individual dislocations and defects is effectively constrained. This results in a substantial improvement in the overall RF electrical characteristics. Based on this proposed process, a coplanar waveguide (CPW) transmission line was fabricated, demonstrating a low RF loss of only -0.6 dB at 40 GHz. These results underscore that the nitridation process is a highly promising pathway for enhancing the RF performance of Si-based GaN materials; more importantly, this study reveals that the advantage of an initially optimized interface must be synergistically integrated and stabilized with subsequent epitaxial processes to achieve low-loss performance in final high-electron-mobility transistor devices, which holds significant implications for the development of high-performance RF devices.

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.