Nanotechnology最新文献

Electrostatic actuators offer a method for tuning photonic components using orders of magnitude less power than competing technologies. We consider electrostatic comb drives with dimensions tailored for integration with silicon photonics and study their static and dynamical properties. We extract the spring constant by dynamical measurements, which do not rely on assumptions about the electrical properties and fringing fields. This, in turn, allows measuring the differential capacitance without making assumptions about the mechanical properties. The resulting data set therefore allows for an accurate assessment of the validity of multiple theoretical models available in the literature, and we identify the importance of the stress in the anchor points for an accurate theoretical description. We provide a comb-drive design, which can be directly applied in silicon photonics, where it is suitable for inducing very large phase shifts and other optical effects in nanoelectromechanical reconfigurable photonic circuits. Through measurements we find that our design can reach mechanical frequencies of 2.7 MHz, the highest operating frequency of a comb-drive actuator reported so far, while still retaining useful steady-state displacements.

AlGaN/GaN based high-electron-mobility transistors utilize the excellent electronic and transport properties of Gallium Nitride and related compounds, making them highly sought after for high-power and high-frequency applications. However, threading dislocations that form during the GaN epitaxy growth on lattice mismatched Si substrates impact the device performance and reliability by causing an early breakdown and carrier trapping phenomena. For applications exceeding 1 kV, the growth of thick GaN stacks on 200 mm Si wafers introduces significant strain, compromising substrate integrity. This has triggered the development of engineered substrates for GaN epitaxy and the re-evaluation of the subsequent epitaxial growth. In this study, we have investigated the current transport properties of detrimental dislocations in AlGaN/GaN heterostructures grown on AlN engineered substrates (commonly referred to as QST^®) and on conventional Si (111) substrates. This study has been achieved by developing a correlative nanoscale characterization methodology implementing conductive atomic force microscopy, cathodoluminescence microscopy, and electron channelling contrast imaging and revisiting dislocation-sensitive etching behavior. This allowed us to observe vertical conduction paths manifesting themselves only in certain types of dislocations and to analyse the associated current transport mechanisms. Our modelling of the local current-voltage characterization on such dislocations, which are only 1% of the total dislocation density, directly associate them to the conduction mechanism via Poole-Frenkel emission in the reverse bias and variable range hopping in the reverse bias.

CsPbBr3 nanoparticles were synthetized by hot-injection using the pair of reagents MnBr2 - SbCl3 and MnBr2 - SbBr3 as doping precursors. Said nanoparticles were green-luminescent (λem = 515 nm) with an average particle size of ~12 nm and with monoclinic and orthorhombic crystal structure lasting longer than 80 days at ambient conditions. Additionally, a 54% photoluminescence quantum yield (PLQY) was maintained for at least 60 days when using MnBr2 - SbBr3 as precursors for doping. Transmission electron microscopy (HRTEM) and electron diffraction (SAED) revealed a reduced interplanar distance for the (110) planes for such condition (dhkl = 0.57 nm - 0.56 nm), suggesting heterogeneous doping into the analyzed nanoparticles, along with chemical analysis. On the other hand, Cl was detected through energy dispersive X-ray spectroscopy (EDXS) in the CsPbBr3 nanoparticles synthetized with the MnBr2 - SbCl3 doping precursor; as a consequence, these nanoparticles displayed a slight blue-shift in their luminescence (λem = 508 nm). Meanwhile, undoped CsPbBr3 nanoparticles decomposed into non-luminescent Cs4PbBr6 with rhombohedral crystal structure before 80 days at ambient condition, as was evidenced by the SAED analysis. Finally, a green-luminescent LED (λem = 519 nm) was fabricated using the doped CsPbBr3 nanoparticles. The achieved stability points to an improvement in the passivation of CsPbBr3's crystal structure through Sb3+ and Mn2+ doping.

High-speed atomic force microscopy enables real-time visualization of molecular dynamics using small cantilevers with high resonance frequencies. To further enhance temporal resolution, cantilevers must be scaled down to achieve higher resonance frequencies while maintaining low spring constants to minimize tip-sample interaction forces and preserve sample integrity. As cantilevers shrink, conventional piezo-based actuation, relying on external actuators to drive the cantilever, becomes less effective due to limited bandwidth and the appearance of spurious resonances in the cantilever spectrum in liquid environments. Photothermal actuation offers clean, high-frequency excitation but often requires high laser powers which can impose a significant thermal load on delicate samples. In this work, we present a wafer-scale microfabrication process for producing ultra-small bimorph cantilevers that combine sub-10 µm lengths, resonance frequencies up to 10.5 MHz, and low spring constants suitable for biological applications. To enhance photothermal actuation efficiency, we substitute the conventional gold coating with palladium, enabling suitable cantilever oscillation at a reduced laser power. We validated the functionality of these cantilevers by imaging a self-assembled DNA lattice of blunt-end stacked DNA three-point stars in buffer.

Solid-liquid gating is a promising route to probe the electrostatics of 2D semiconductors, yet its mechanisms are easily obscured by interface defects and discharge paths introduced by ionic double layers in conventional measurement circuits. We address these issues with two advances: (i) a damage-free all-solid-liquid contact that suppresses interface degradation and trapping, and (ii) a measurement architecture that isolates the ionic-liquid (IL) double layer from circuit discharge, employing an ultrahigh-input-impedance follower to read the gate potential in operando. These measures deliver accurate and highly reproducible gate potentials. With this direct potential metrology, we measured the IL potential at the mid-channel, providing a more direct basis for explaining the apparent long-channel pinch-off effect. Crucially, we find that threshold voltage shifts correlate with the gate metals' intrinsic open-circuit potentials (OCPs), not their work-function differences, overturning a common assumption. Together, these results clarify the mechanism of solid-liquid gating and establish a reliable foundation for designing low-power, solution-gated nanoelectronics.

Dirac semi-metals have emerged as excellent metal electrodes for two-dimensional semi- conductors, owing to their high in-plane conductivity, weak metallization at the interface and work function tunability by gate voltages and strains. Herein, we investigate the potential of a Dirac semi-metal FeB₂as high performance electrode material using density functional theory (DFT). We study its interfaces with transition metal dichalcogenide (TMDs: MoS₂, WS2) and Janus transition metal dichalcogenide (JTMDs: MoSSe, WSSe) semiconductors. We construct novel van der Waals metal-semiconductor interfaces (vdW-MSIs) by stacking FeB₂monolayer on top of semiconductor layers and systematically examine the effects of stacking order and external electric fields on their electronic properties. We show that elec- tric coupling between FeB₂and semiconducting layers result in ultra-low n-type and p-type Schottky barriers. These barriers are sensitive to both electric fields and stacking, enabling transitions between n-type, p-type and Ohmic contacts. Additionally, the interfaces exhibit ultralow tunneling resistivity, offering favorable balance between Schottky and tunneling barriers. The efficient barrier control and minimal tunneling resistances are in line with International Roadmap for Devices and Systems(IRDS) standards. These findings expand the Dirac semi-metal family as a high quality contact and provide comprehensive theoretical insights for developing future sub-nm scaled FETs utilizing FeB₂.

Two-dimensional (2D) materials offer an exceptional platform for exploring quantum phenomena, as their reduced dimensionality significantly enhances tunability via external parameters. Among these, superconductivity in 2D systems is of particular interest due to its fundamental significance and potential applications in quantum technologies. Despite ongoing experimental challenges in realizing novel 2D superconductors, first-principles calculations have emerged as powerful tools for guiding their prediction and design. While many prior reviews focus broadly on low-dimensional superconductivity, this article specifically surveys computationally predicted 2D superconductors, with an emphasis on the underlying theoretical frameworks and their limitations. We highlight how external perturbations such as strain, doping, chemical functionalization, and intercalation, modify electron-phonon coupling and superconducting critical temperatures, and we examine cases where superconductivity competes or coexists with other quantum orders, including charge density waves and nontrivial band topology. We further discuss the growing role of machine-learning and high-throughput approaches in accelerating materials discovery, along with the challenges associated with data quality and model reliability. Overall, this review underscores the potential and current limitations of first-principles and data-driven approaches in advancing the understanding and discovery of 2D superconductors.

Graphyne (GY) nanomaterials, with their highly tunable properties, show great potential as building blocks for composite nanodevices. Using molecular dynamics simulations, this study investigates the bi-directional folding and unfolding evolution of homogeneous and heterogeneous GY nanoribbons (GYNRs) around a rotating carbon nanotube (CNT). The results reveal distinct configuration rules: homogeneous GYNRs consistently undergo synchronous folding to form interlaced GY nanoscrolls (GYNSs), whereas heterogeneous GYNRs may fold synchronously or in a layered manner, producing either interlaced or covered GYNSs depending on atomic density differences (ADDs) and temperature. Moreover, GYNSs can be reversibly unfolded into GYNRs under CNT rotation. Unified unfolding, initiated from the innermost layer, typically occurs in interlaced GYNSs, while segmented unfolding-unique to covered GYNSs with large ADDs-proceeds sequentially from the outermost edge of the outer GYNS to the innermost layer of the inner GYNS. These findings establish key principles for the flexible design and engineering of novel homo- and heterogeneous GY-based nanostructures.

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.