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Investigating the phonon-surface scattering mechanism is essential for the evaluation of thermal transport in nanostructures. The theoretical description to quantify this mechanism remains to be developed at the atomic scale. This work presents a phonon wave packet method to study the phonon-surface scattering behavior at rough surfaces. We obtain the specularity distribution dependent on phonon polarization, wavelength, and surface roughness. The reflection of the diffuse wave packet is primarily attributed to the surface shadowing effect at a higher incident angle, surface disorder, and surface-induced localized modes. Taking the wavevector-dependent specularity data as input, the thermal conductivity of silicon nanowires is calculated based on the Boltzmann Transport Equation. Our specularity model provides an accurate evaluation for predicting thermal conductivity. This work offers an atomic-level analysis for phonon-surface interaction, which is helpful for the understanding of thermal transport in nanostructures. [ABSTRACT FROM AUTHOR]

Silicon, renowned for its remarkable energy density, has emerged as a focal point in the pursuit of high-energy storage solutions for the next generation. Nevertheless, silicon electrodes are known to undergo significant volume expansion during the insertion of lithium ions, leading to structural deformation and the development of internal stresses, and causing a rapid decline in battery capacity and overall lifespan. To gain deeper insights into the intricacies of charge rate effects, this study employs a combination of in situ measurements and computational modeling to elucidate the cyclic performance of composite silicon electrodes. The findings derived from the established model and curvature measurement system unveil the substantial alterations in stress and deformation as a consequence of varying charge rates. Notably, the active layer experiences compressive forces that diminish as the charge rate decreases. At a charge rate of 0.2, the active layer endures a maximum stress of 89.145 MPa, providing a comprehensive explanation for the observed deterioration in cycling performance at higher charge rates. This study not only establishes a fundamental basis for subsequent stress analyses of silicon electrodes but also lays a solid foundation for further exploration of the impact of charge rates on composite silicon electrodes. [ABSTRACT FROM AUTHOR]

The laser power mediated changes in the Raman line shape have been considered in terms of interference between discrete phonon states ρ and the electronic continuum states ϰ contributed by Urbach tail states. The laser-induced effects are treated in terms of the increase in the surface temperature and thereby the scaling of electronic disorder, i.e., Urbach energy, which can further contribute to the electron–phonon interactions. Therefore, the visualization of this effect is attempted analytically as a perturbation term in the Hamiltonian, which clearly accounts for the observed changes with laser power. This has been investigated based on the experimental results of laser power dependent Raman spectra of bulk EuFeO3 and silicon nanowires, which are found to provide convincing interpretations. [ABSTRACT FROM AUTHOR]

Metal–Organic Polymers (MOPs) have attracted growing attention for lithium-ion battery (LIB) applications due to their merits in orderly ionic transportation and robust structure stability in electrochemical reactions. However, they suffer from poor electronic conductivity. In this work, we apply first-principles density functional theory to explore the potential of three one-dimensional (1D) electrically conductive C6H2S4TM (TM = Fe, Co, and Ni) MOPs with the π–d conjugated coordination as anode materials for Li+ ions storage. Our theoretical results reveal that these 1D MOPs possess a superior theoretical capacity of over 748 mA h g−1. In particular, the 1D C6H2S4Ni MOP shows an exceptional theoretical specific capacity of 1110 mA h g−1 based on the three-electron transferring reaction, which significantly outperforms the traditional graphite-based anode material in LIBs. Moreover, the resonant charge transfer between Ni metal and ligand within the 1D C6H2S4Ni MOP reduces the diffusion energy barrier of the Li atoms when they migrate on the surface of the MOP. The ultrahigh theoretical specific capacity of the C6H2S4Ni MOP predicts that it can be a promising anode material for LIBs. [ABSTRACT FROM AUTHOR]

An analytical device physics model is presented for determining the energy conversion efficiency of semiconductor nanowire array-based radial (core–shell) p-i-n junction betavoltaic cells for two- and three-dimensional radioisotope source geometries. Optimum short-circuit current density J sc , open-circuit voltage V oc , fill factor F F , and energy conversion efficiency η are determined for various nanowire properties, including dopant concentration, nanowire length, core diameter, and shell thickness, for Si, GaAs, and GaP material systems. A maximum efficiency of 8.05 % was obtained for GaP nanowires with diameter 200 nm (p-core diameter, i-shell, and n-shell thicknesses of 24, 29.4, and 58.6 nm, respectively), length 10 μ m , acceptor and donor concentrations of 10 19 and 5 × 10 18 cm − 3 , respectively, and a 3D source geometry. [ABSTRACT FROM AUTHOR]

Hyperdoped silicon is a promising material for near-infrared light detection, but to date, the device efficiency has been limited. To optimize photodetectors based on this material that operate at room temperature, we present a detailed study on the electrical nature of gold-hyperdoped silicon formed via ion implantation and pulsed-laser melting (PLM). After PLM processing, oxygen-rich and gold-rich surface layers were identified and a wet etch process was developed to remove them. Resistivity and Hall effect measurements were performed at various stages of device processing. The underlying gold-hyperdoped silicon was found to be semi-insulating, regardless of whether the surface gold was removed by etching or not. We propose a Fermi level pinning model to describe the band bending of the transformed surface layer and propose a promising device architecture for efficient Au-hyperdoped Si photodetectors. [ABSTRACT FROM AUTHOR]

Roughly, 50% of primary energy worldwide is rejected as waste heat over a wide range of temperatures. Waste heat above 573 K has the highest Carnot potential (> --> 50 %) to be converted to electricity due to higher Carnot efficiency. Thermoelectric (TE) materials have gained significant attention as potential candidates for efficient thermal energy conversion devices. Silicon nanowires (SiNWs) are promising materials for TE devices due to their unique electrical and thermal properties. In this study, we report the successful fabrication of high-quality double-sided SiNW arrays using advanced techniques. We engineered the double-sided structure to increase the surface area and the number of TE junctions, enhancing TE energy conversion efficiency. We also employed non-agglomeration wire tip engineering to ensure uniformity of the SiNWs and designed effective Ohmic contacts to improve overall TE efficiency. Additionally, we post-doped the double-sided SiNW arrays to achieve high electrical conductivity. Our results showed a significant improvement in the TE performance of the SiNW array devices, with a maximum figure-of-merit (ZT) value of 0.24 at 700 K, fabricated from the single SiNW with ZT of 0.71 at 700 K in our previous work [Yang et al., Nat. Commun. 12(1), 3926(2021)]. [ABSTRACT FROM AUTHOR]

Copper (Cu) interconnections have been widely used in advanced electronic packaging due to their outstanding thermal and electric properties. Preparing a smooth and uniform Cu seed thin layer is one of the critical processes to obtain high-reliability Cu interconnections. The barrier layer between Cu and silicon (Si) devices is necessary to prevent the inter-diffusion between Cu and Si. However, little work has been done on the surface roughness analysis of the Cu seed layer deposited on the diffusion barrier layer. In this paper, the influences of deposition thickness, incident energy, barrier layer temperature, and surface morphology on the surface roughness of the Cu seed layer deposited on α-titanium (α-Ti) barrier layer were studied in detail by the molecular dynamics (MD). The simulation results indicated that appropriate parameters have a beneficial effect on reducing the surface roughness, and the surface morphology of the Cu seed layer strongly connects with that of the barrier layer. These results provided a foundation for optimizing the quality of the Cu seed layer. [ABSTRACT FROM AUTHOR]

Based on the transport and polarization relaxation theories, the effects of hydrogen, fluorine, and chlorine atom passivation on the conductivity and dielectric properties of silicon carbide nanowires (SiCNWs) were numerically simulated. The results show that passivation can decrease the dark conductivity of SiCNWs and increase its ultraviolet photoconductivity. Among them, the photoconductivity of univalent (H) passivated SiCNWs is better than that of seven-valent (Cl, F) passivated SiCNWs. In terms of dielectric properties, the passivated SiCNWs exhibit a strong dielectric response in both deep ultraviolet and microwave regions. Hydrogen passivation SiCNWs produce the strongest dielectric response in deep ultraviolet, while fluorine passivation SiCNWs produce the strongest dielectric relaxation in the microwave band, which indicates that atomic passivation SiCNWs have a wide range of applications in ultraviolet optoelectronic devices and microwave absorption and shielding. [ABSTRACT FROM AUTHOR]

It is a formidable challenge to find the minority carrier recombination lifetime in low-dimensional devices as low-dimensionality increases the surface recombination rate and often reduces the recombination lifetime to a scale of picoseconds. In this work, we demonstrated a simple but powerful method to quantitatively probe the minority carrier recombination lifetime in silicon nanowires or microwires by fitting the experimental photoresponses with our recently established analytical photoresponse principle of photoconductors. The nanowires were passivated with small molecules and Al2O3 to suppress surface recombination, which will increase the minority recombination lifetimes. As expected, the minority carrier recombination lifetime found by this approach increases by orders of magnitude. These wires were also made into PIN diodes, the leakage of which was reduced at least 1 order of magnitude after surface passivation by Al2O3. The minority recombination lifetime found from the leakage current of these devices is largely consistent with what we found from our analytical photoresponse principle. As a further step, we performed scanning photocurrent microscopy to find the minority diffusion length from which we found that the minority recombination lifetime is close to what we found from the analytical photoresponses. In short, this work validated that our analytical response principle is a reliable method to find the minority recombination lifetime in low-dimensional semiconductors. [ABSTRACT FROM AUTHOR]

Fabrication of modern solid-state devices demands precise control of shape and dimensions, which requires an accurate knowledge of the role that surfaces play in such devices. To contribute to the understanding of surface effects on silicon nanowires, we present an atomistic study of the electronic properties of silicon nanostructures exhibiting surface facets over the (100) , (110) , (111) , and (112) crystallographic planes. We calculate the electronic structure of slabs in such a way that the effect of individual facets may be observed. Subsequently, we determine the electronic structure of nanowires grown along the [ 100 ] , [ 110 ] , [ 111 ] , and [ 112 ] directions, with surfaces defined by a combination of the mentioned facets. Our nanowires comprise diameters ranging from 1 to 6.7 nm and structures with more than 1000 atoms. We discuss the band structure, the relation between direct and indirect bandgaps, and the density of states. We base our calculations on semiempirical pseudopotentials where we implement complex potentials to describe passivants. We find that there is a transition from direct to indirect gap for the [ 111 ] direction at approximately 2 nm and that the difference between the direct and indirect gap may reach more than 300 meV depending on the diameter. We show that the occurrence of a direct bandgap is favored by the presence of the (100) facet and that it is related to a higher surface density of states. Conversely, we find that the (111) facet is the most inert surface type with a lower surface density of states. [ABSTRACT FROM AUTHOR]

Si 3 N 4 and SPEEK were simply mixed and used to prepare a Si 3 N 4 /SPEEK composite separator through electrospinning. The silicon nanowires formed at the interface between the Si 3 N 4 /SPEEK separator and the lithium anode result in the separator showing superior long-cycle performance. [Display omitted] • The Si 3 N 4 /SPEEK composite separator was prepared by electrospinning. • Si 3 N 4 in the Si 3 N 4 /SPEEK separator can be reduced by Li+ to form Si nanowires. • The Si 3 N 4 /SPEEK separator features a high specific surface area and abundant mesopores. • DFT calculations reveal that Si 3 N 4 has strong interactions with electrolyte molecules (EC and DMC). • Si 3 N 4 enhances the dimensional stability of separator at high temperatures and pressures. The uncontrolled lithium (Li) dendrite growth significantly impacts the safety performance of polymer separators. To mitigate this growth, this study introduces Si 3 N 4 into sulfonated poly(ether Ether Ketone) (SPEEK) and prepares Si 3 N 4 /SPEEK composite separators via electrospinning. At the interface between the Si 3 N 4 /SPEEK separator and the Li anode, the Si nanowires that form impede Li dendrite growth, thereby enhancing the electrochemical performance of lithium-ion batteries (LIBs). The Li deposition test of the 10 % Si 3 N 4 /SPEEK separator can operate for 1000 h without short-circuiting. Additionally, the LiFePO 4 ||Li cell with the 10 % Si 3 N 4 /SPEEK separator shows improved initial discharge capacity (157.8 mAh g−1 at 1C) and superior rate performance (125 mAh g−1 at 10C). Moreover, the nano-scale Si 3 N 4 endows the separator with robust thermal and mechanical properties. The FLIR observations reveal that the 10 % Si 3 N 4 /SPEEK separator maintains uniform thermal distribution and structural integrity even at 300 °C, ensuring safe battery operation at high temperatures. The additional load of the 10 % Si 3 N 4 /SPEEK separator can reach 10.2 mN, which enhances the puncture resistance of the separator. This work provides a solid approach for the application of SPEEK as a high-safety and high-rate LIB separator. [ABSTRACT FROM AUTHOR]

Enhancing critical heat flux (CHF) and heat transfer coefficient (HTC) by promoting the nucleation, growth, and departure of boiling bubbles has drawn significant attention owing to its wide applications. However, in‐depth understanding and comprehensive manipulation of under‐liquid bubble dynamics from in situ microscale perspectives remain challenging. Herein, in situ observations and analyses of the microsized boiling bubbles of ultra‐low surface tension fluorinated liquids (FLs) are conducted on the superaerophobic silicon surfaces with crisscross microchannels and selective nanowires. It is revealed that deep microchannels yet short nanowires enable ultrafast liquid spreading (<549.6 ms) and ultralow bubble adhesion (≈1.1 µN), while an appropriate spacing (240–600 µm) between microchannels minimizes the bubble departure time (<20.6 ms) due to timely coalescence. By verifying the above bubble dynamics principles through the collaborative enhancement of CHF and HTC, an optimized structure (microchannel depth ≈52.9 µm, microchannel spacing ≈362.9 µm, nanowire length ≈0 nm) is obtained and further implemented onto the exposed Si surface of a commercial CPU chip. Cooled by phase‐change of FLs, the average temperature of CPU maintains ≈64.9 °C even under extreme power loads (≈130 W), far below than those in conventional air‐cooling and water‐cooling operations. [ABSTRACT FROM AUTHOR]

Among numerous approaches to assembling nanowires onto electrodes, dielectrophoresis (DEP) is a potential candidate to place the nanowires. However, its yield is still far from perfection, urging fundamental understanding of its dynamics. Here, the impact of a static electric field on dielectrophoretic nanowire assembly on gold electrodes is investigated. Specifically, a 4 peak‐to‐peak alternating voltage with 700 Hz is applied and modulate the offset voltage from 0 to 2V. The highest yield in the alignment of the nanowires at 0.5 V offset voltage is found. With the optical investigation of misaligned nanowires, it is found that rotating wires on top of electrodes, and the analysis of their angular velocity suggest the impact of the induced static charges. The numerical analysis quantifies the length scale of competing two forces, dielectrophoretic force and electric double layer force. This work suggests a quantitative understanding of the interplay between dielectrophoresis and electric double layer, which contributes to the advances in scalable nanowire fabrications. [ABSTRACT FROM AUTHOR]

The development of ion-sensitive field-effect transistor (ISFET) sensors based on silicon nanowires (SiNW) has recently seen significant progress, due to their many advantages such as compact size, low cost, robustness and real-time portability. However, little work has been done to predict the performance of SiNW-ISFET sensors. The present study focuses on predicting the performance of the silicon nanowire (SiNW)-based ISFET sensor using four machine learning techniques, namely multilayer perceptron (MLP), nonlinear regression (NLR), support vector regression (SVR) and extra tree regression (ETR). The proposed ML algorithms are trained and validated using experimental measurements of the SiNW-ISFET sensor. The results obtained show a better predictive ability of extra tree regression (ETR) compared to other techniques, with a low RMSE of 1 × 10−3 mA and an R2 value of 0.9999725. This prediction study corrects the problems associated with SiNW -ISFET sensors. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Photocatalysis is a promising green approach for water purification. The diversity of water pH values is a key factor that restricts its practical application since pH affects the adsorption of organic molecules, the stability of catalysts and photocatalytic performance. Here, we report a pH–independent, efficient and stable photocatalytic system with a liquid (water)–liquid (oil)–solid (semiconductor) (L–L–S) triphase interface microenvironment. The system is fabricated by coating a thin layer of silicon oil on the surface of ZnO nanowire arrays, a model chemically unstable semiconductor in both acidic and alkaline solutions. We show that the unique interface makes the dye adsorption pH independent and prevents the semiconductor from being corroded by strong acidic/alkaline solutions, leading to a stable and efficient photocatalytic reaction over a wide pH range (1—14). These findings reveal a promising path for the development of high‐performance catalysis systems applicable in complex water environments. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Photocatalysis is a promising green approach for water purification. The diversity of water pH values is a key factor that restricts its practical application since pH affects the adsorption of organic molecules, the stability of catalysts and photocatalytic performance. Here, we report a pH–independent, efficient and stable photocatalytic system with a liquid (water)–liquid (oil)–solid (semiconductor) (L–L–S) triphase interface microenvironment. The system is fabricated by coating a thin layer of silicon oil on the surface of ZnO nanowire arrays, a model chemically unstable semiconductor in both acidic and alkaline solutions. We show that the unique interface makes the dye adsorption pH independent and prevents the semiconductor from being corroded by strong acidic/alkaline solutions, leading to a stable and efficient photocatalytic reaction over a wide pH range (1—14). These findings reveal a promising path for the development of high‐performance catalysis systems applicable in complex water environments. [ABSTRACT FROM AUTHOR]

In this paper, Zinc Oxide nanoparticles (ZnO NPs) have been successfully synthesized for the first time by electrochemical deposition on silicon nanowires (SiNWs) produced using silver-assisted chemical etching method. The as-prepared nanowires were pre-coated with ZnO seed layer to initialize the uniform growth of ZnO nanoparticles from aqueous solutions using the electrochemical deposition. The SEM images showed a homogenous distribution of dense ZnO nanoparticles on silicon nanowires. X-ray diffraction pattern indicated that the electrodeposited ZnO NPs have hexagonal wurtzite structure. Current–voltage characteristics pointed that ZnO NPs significantly improved the diode parameters such as ideality factor (n), series resistance ( R s ), energy barrier ( φ b ) and saturation current ( I s ). As a result, a rectifying behavior of the ZnO NPs/SiNWs structure has been exhibited by a factor of 2.7 compared to pure SiNWs structures. The values of the saturation current I s and the series resistance R s of these heterostructures decrease indicating an improvement in junction quality which can be due to the reduction of dangling bonds and surface defects. Significantly, ZnO nanoparticles @SiNWs increased the minority carrier lifetime from 9.11 μ s to 14.89 μ s and consequently reduced the surface recombination activities, further revealing the efficient surface passivation role of ZnO nanoparticles. Good anti-reflectance abilities up to 10% and 15% are observed for pure SiNWs and SiNWs/ZnO NPs, respectively, as compared to 40% for bare Silicon. Based on these findings, SiNWs/ZnO NPs can be considered as potential candidate for optoelectronic devices, photovoltaics and nanoelectronics. [ABSTRACT FROM AUTHOR]

Wearable wireless gas sensors have attracted enormous interest due to precise, real‐time healthcare and environmental monitoring without temporal and spatial limitations. Among various toxic gases, detecting ammonia is crucial because of its highly hazardous nature and applicability as a noninvasive biomarker for diagnosing health conditions. In this study, silver nanowires‐decorated silicon nanomembrane (AgNW‐SiNM) chemiresistive gas sensor with high selectivity to ammonia is fully integrated with an ultrathin flexible Joule heater and wireless communication system to fabricate wearable wireless real‐time toxic gas monitoring system. The sensor exhibits improved performance to ammonia gas, attributed to heating‐induced changes in adsorption/desorption rates, along with electronic and chemical sensitization facilitated by AgNW decoration. The gas sensing system exhibits stable and high responses of ≈1.83, 1.47, and 1.19 on the ammonia exposure at concentrations of 10, 5, and 1 ppm even under mechanical deformations. The real‐time dynamic response of the sensor is wirelessly transmitted to portable electronics and displayed on the screen. Moreover, the system alerts the users in advance through the integrated haptic interface when exposed to dangerous gas environments for early evacuation. The system paves the way for timely warnings from hazardous gas and more accurate noninvasive medical diagnosis related to respiratory disorders. [ABSTRACT FROM AUTHOR]

The effects of very low temperature on the electron transport in a [110] and [100] axially aligned unstrained silicon nanowires (SiNWs) are investigated. A combination of semi-empirical 10-orbital tight-binding method, density functional theory and Ensemble Monte Carlo (EMC) methods are used. Both acoustic and optical phonons are included in the electron-phonon scattering rate calculations covering both intra-subband and inter-subband events. A comparison with room temperature (300 K) characteristics shows that for both nanowires, the average electron steady-state drift velocity increases at least 2 times at relatively moderate electric fields and lower temperatures. Furthermore, the average drift velocity in [110] nanowires is 50 percent more than that of [100] nanowires, explained by the difference in their conduction subband effective mass. Transient average electron velocity suggests that there is a pronounced streaming electron motion at low temperature which is attributed to the reduced electron-phonon scattering rates. [ABSTRACT FROM AUTHOR]

At present, the preparation of absorbing materials that combine light weight, ultra-wideband absorption and good thermal insulation performance is still an insurmountable gap. Here, we constructed a three-dimensional porous structure in the hope of obtaining excellent microwave absorption and heat insulation properties. In this paper, a unique three-dimensional porous SiCNWs/Ti3C2Tx/RGO (STR) aerogel was prepared by hydrothermal treatment. When the mass ratio of SiCNWs, Ti3C2Tx and GO is 2:1:1, the effective absorption bandwidth of STR aerogel reaches 8.10 GHz (9.90–18.00 GHz). Moreover, the porous structure can effectively reduce the heat radiation transfer. After heating at 300 ℃ for 1 h, STR aerogel can effectively isolate the temperature of about 160 ℃, which proves that STR has good thermal insulation performance. In addition, the formation mechanism of the STR aerogels and the mechanism of thermal insulation and electromagnetic wave absorption of aerogels are also discussed, which will contribute to the development and application of new lightweight stealth material. [ABSTRACT FROM AUTHOR]

This study explores the hydrogen generation potential via water-splitting reactions under UV-vis radiation by using a synergistic assembly of ZnO nanoparticles integrated with MoS2, single-walled carbon nanotubes (SWNTs), and crystalline silicon nanowires (SiNWs) to create the MoS2-SiNWs-SWNTs@ZnONPs nanocomposites. A comparative analysis of MoS2 synthesized through chemical and physical exfoliation methods revealed that the chemically exfoliated MoS2 exhibited superior performance, thereby being selected for all subsequent measurements. The nanostructured materials demonstrated exceptional surface characteristics, with specific surface areas exceeding 300 m2 g−1. Notably, the hydrogen production rate achieved by a composite comprising 5% MoS2, 1.7% SiNWs, and 13.3% SWNTs at an 80% ZnONPs base was approximately 3909 µmol h−1g−1 under 500 nm wavelength radiation, marking a significant improvement of over 40-fold relative to pristine ZnONPs. This enhancement underscores the remarkable photocatalytic efficiency of the composites, maintaining high hydrogen production rates above 1500 µmol h−1g−1 even under radiation wavelengths exceeding 600 nm. Furthermore, the potential of these composites for energy storage and conversion applications, specifically within rechargeable lithium-ion batteries, was investigated. Composites, similar to those utilized for hydrogen production but excluding ZnONPs to address its limited theoretical capacity and electrical conductivity, were developed. The focus was on utilizing MoS2, SiNWs, and SWNTs as anode materials for Li-ion batteries. This strategic combination significantly improved the electronic conductivity and mechanical stability of the composite. Specifically, the composite with 56% MoS2, 24% SiNWs, and 20% SWNTs offered remarkable cyclic performance with high specific capacity values, achieving a complete stability of 1000 mA h g−1 after 100 cycles at 1 A g−1. These results illuminate the dual utility of the composites, not only as innovative catalysts for hydrogen production but also as advanced materials for energy storage technologies, showcasing their potential in contributing to sustainable energy solutions. [ABSTRACT FROM AUTHOR]

This study investigates the growth of gallium arsenide nanowires, using lead as a catalyst. Typically, nanowires are grown through the vapor–solid–liquid mechanism, where a key factor is the reduction in the nucleation barrier beneath the catalyst droplet. Arsenic exhibits limited solubility in conventional catalysts; however, this research explores an alternative scenario in which lead serves as a solvent for arsenic, while gallium and lead are immiscible liquids. Liquid lead easily dissolves in Si as well as in GaAs. The preservation of the catalyst during the growth process is also addressed. GaAs nanowires have been grown by molecular beam epitaxy on silicon Si (111) substrates at varying temperatures. Observations indicate the spontaneous doping of the GaAs nanowires with both lead and silicon. These findings contribute to a deeper understanding of the VLS mechanism involved in nanowire growth. They are also an important step in the study of GaAs nanowire-doping processes. [ABSTRACT FROM AUTHOR]

Changes in the interfacial structures of the amorphous silicon (a-Si) anode/organic electrolyte interfaces in lithium-ion batteries were investigated using highly dense a-Si films fabricated by cathodic arc plasma deposition as a model electrode. Raman spectroscopy, transmission electron microscopy (TEM), and X-ray reflectivity revealed that the Si films were grown in an amorphous state with an atomically flat surface. The a-Si films exhibited lithium alloying and de-alloying reactions, with a large irreversible capacity during the first cycle. The irreversible capacity was derived from the formation of a solid electrolyte interphase (SEI) along with an incompletely de-alloyed Li-Si phase, as confirmed by ex situ TEM and X-ray photoelectron spectroscopy observations. The discharge and charge capacities of the Si films gradually decreased in the subsequent cycles, despite the fact that no further SEI formation or cracking of the Si layer occurred. Scanning electron microscopy observations combined with energy-dispersive X-ray spectroscopy revealed the miniaturization of the a-Si film in the surface region to generate domains measuring less than a few hundred nanometers. These results suggest that delamination and miniaturization of the a-Si nanodomains from the electrode surface are partly responsible for degradation of the a-Si anode. [ABSTRACT FROM AUTHOR]

Using large scale molecular dynamics simulations, we study the thermal conductivity of bare and surface passivated silicon nanowires (SiNWs). For the cross–sectional widths w ⩽ 2 nm, SiNWs become unstable because of the surface amorphization and also due to the evaporation of a certain fraction of Si atoms. The observed surface (in–)stability is related to a large excess energy Δ of the surface Si atoms with respect to the bulk Si, resulting from the surface atoms being less coordinated and having dangling bonds. We first propose a practically relevant method that uses Δ as a guiding tool to passivate these dangling bonds with hydrogen or oxygen, stabilizing the SiNWs. These passivated SiNWs are used to calculate the thermal conductivity coefficient κ. While the expected trend of κ ∝ w is observed for all SiNWs, surface passivation provides an added flexibility of tuning κ with the surface coverage concentration c of passivated atoms. Indeed, with respect to the bulk κ, passivation of SiNW reduces κ by 75%–80% for c → 50 % and increases it by 50% for the fully passivated samples. Analyzing the phonon band structures via spectral energy density, we discuss separate contributions from the surface and the core to κ. Our results also reveal that surface passivation increases SiNW stiffness, contributing to the tunability in κ. [ABSTRACT FROM AUTHOR]

Water contamination due to significant industrialization and urbanization has drawn the attention of numerous researchers to water remediation techniques like photocatalysis. The intriguing characteristics of silicon nanowires (SiNWs), like light trapping and catalytic activity for the removal of textile dyes, have drawn attention to this material. In this work, the synthesis of SiNWs and their modifications with metal particles like copper or silver with different concentrations has been reported. Metal‐assisted chemical etching, a cost‐effective and easy method, is used to synthesis SiNWs with an optimized aspect ratio. The as‐prepared materials and it photocatalysis performance are studied by X‐ray diffraction (XRD), field emission and transmission electron microscope (FESEM, TEM), and UV–visible spectroscopy. The XRD confirms the presence of the copper particles on SiNWs. The FESEM image reveals the formation of flower‐like structures with different morphologies for silver and copper‐modified SiNWs. The as‐prepared samples have shown efficacy in removing Rhodamine‐B by the process of photocatalysis under irradiation with UV light. It has been observed that when the concentration of the copper nanoparticles is increased, a significant increase in the photocatalytic activity is obtained. The removal efficiency came within the range of 50–65%. [ABSTRACT FROM AUTHOR]

For the preparation of SiC nanowires (SiC NWs) by carbothermal reduction, it is of great significance to study the formation mechanism of sic nanowires for process optimization and the controllable preparation. Although first-principles molecular dynamics (FPMD) can simulate systems of hundreds of atoms on a picosecond time scale, the results of FPMD are still insufficient to elucidate the formation mechanism of core-shell SiC nanowires. To make up this deficiency, this article has conducted Deep Potential Molecular Dynamics (DPMD) simulation on nanoseconds timescales with near FPMD accuracy for systems containing thousands of atoms, the results more concretively show the formation process of core-shell SiC nanowires. DPMD simulation results show when CO molecules react with SiO molecules, CO molecules are wrapped by SiO molecules to form agglomerates, SiO molecules in the agglomerates that can come into contact with the wrapped CO molecules will react with wrapped CO molecules to form the SiC core, and SiO molecules that in the outer layer of the agglomerates will disproportionate into the amorphous SiO 2 shell. Furthermore, the formation mechanism of SiC nanowires was validated in combination with thermodynamics and experimental methods. Thermodynamic results show that vacuum conditions are favorable for the formation of SiO and CO and lower the temperature of SiC preparation. Finally, the core-shell structure of SiC NWs with good luminescence properties were successfully prepared by carbothermal reduction method using carbon black and silicon dioxide as raw materials under the pressure of less than 5 kPa. [ABSTRACT FROM AUTHOR]

Stacking faults (SFs) could be generated in aluminum (Al) via full dislocations extension under extreme stress. However, the extension behavior of the dislocations related to the stress conditions have not been studied comprehensively. In this study, SFs were generated solely under extreme stress condition in coarse–grained Al nanocomposites, where high content of Silicon Carbide nanowires (SiCnw) was introduced as reinforcement. Dislocation extension behaviors under normal and shear stress were predicted using an atomistic approach comparing with experiment methods. The extension ability of full dislocations was studied in terms of complex stress forced on partial dislocations and the relationship between stress condition and the SF width was established by stress analysis. The generated SFs were further proved to offer superb additional strengthening effect for the composites. This study provides a new idea and theory for designing of SF generation in coarse–grained Al based nanocomposites. [ABSTRACT FROM AUTHOR]

Silicon nanowires (SiNWs) have garnered considerable attention in the last few decades owing to their versatile applications. One extremely desirable aspect of fabricating SiNWs is controlling their dimensions and alignment. In addition, strict control of surface roughness or diameter modulation is another key parameter for enhanced performance in applications such as photovoltaics, thermoelectric devices, etc. This study investigates a method of fabricating silicon nanowires using electron beam lithography (EBL) and the deep reactive ion etching (DRIE) Bosch process to achieve precisely controlled fabrication. The fabricated nanowires had a pitch error within 2% of the pitch of the direct writing mask. The maximum error in the average diameter was close to 25%. The simplified two-step method with tight control of the dimensions and surface tunability presents a reliable technique to fabricate vertically aligned SiNWs for some targeted applications. [ABSTRACT FROM AUTHOR]

In GaN‐on‐Si nanowire integration schemes, where the nanowires are contacted through the substrate, the interfaces between silicon substrate, AlN buffer layer, and GaN nanowire are of high interest. Herein, analysis by scanning transmission electron microscopy (STEM) of GaN nanowires grown on Si(111) by metal–organic vapor phase epitaxy using a polarity‐ and site‐controlled growth method is presented. This method is based on prestructuring the substrate, ex situ oxidation of the surface, and in situ oxide layer desorption. First, an AlN layer is grown to prevent melt‐back etching. Samples are prepared for STEM by focused ion beam cutting. STEM measurements in three different regions reveal that the AlN buffer material is polycrystalline. The degree of polycrystallinity is found to depend on the observed region: the highest degree exists at the field area between nanowires and the lowest at the sidewall of the Si‐pillars. On the sidewall, the c→$$ \overrightarrow{c} $$‐direction of the AlN grain is tilted by 30.1° with regard to the Si{111} sidewall plane, leading to reduced lattice mismatch at this location. The growth of GaN is competing with diffusion of Ga atoms through grain boundaries. The dominant mechanism is dependent on the region, leading to site‐controlled growth of nanowires. [ABSTRACT FROM AUTHOR]

A significant (up to 4 times) photoluminescence enhancement of single InP/InAsP/InP nanowires transferred onto a silicon oxide‐covered silver layer on silicon substrate with a metal surface roughness level of less than 1 nm and a dielectric thickness of 5 nm has been demonstrated. This phenomenon is explained by the interaction of electron–hole pairs in the semiconductor with surface plasmon polaritons. The photoluminescence kinetics and results of modeling confirm the indicated enhancement mechanism. [ABSTRACT FROM AUTHOR]

This study employed a computational approach, particularly Density Functional Theory at B3LYP−D3/6‐31+G(d) level to design two new classes of three‐dimensional (3D) Lantern Organic Frameworks (LOFs) materials based on trisilasumanene and porphyrin core building units. Particularly, we detail strategies for transitioning from 1D‐LOF nanowires to extended 3D structures: first by connecting planar‐molecule base units of trisilasumanene or porphyrin using benzene‐based linkers, and then connecting silicon anchoring atoms on the bases with other bases that are vertically stacked by sp3‐hydrocarbon chains. The 3D‐LOF structures are designed to have different pore sizes through the use of various bases, bridges, and linkers. Comparisons of electronic properties of these 3D structures lead to one designing rule. That is, the gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the 3D materials depends only on its base and is nearly independent of the stack size or the length of the sp3‐hydrocarbon bridges. Additionally, connecting base units with linkers also extends π‐electron conjugation system leading to a reduction in HOMO‐LUMO gap. For instance, linking two trisilasumanene molecules significantly narrows HOMO‐LUMO gap by 1.75 eV while stacking these bases vertically and connecting them by linear pentane‐based bridges yield insignificant change to the gap. [ABSTRACT FROM AUTHOR]

A novel subthreshold drain current model has been developed for a cylindrical gate all‐around junctionless transistor with three different gate materials. The proposed device is built with three gate regions of different work functions that effectively reduce the short‐channel effects caused by quantum mechanical effects. The drain current equation is solved for all three operating regions to investigate the device switching characteristics and minimize the drain‐induced barrier lowering (DIBL), velocity saturation, mobility degradation, and tunneling. It is understood that the triple material gate structure enhances the transport efficiency of the device. The proposed analytical model is validated by comparison with Sentaurus TCAD numerical simulator results and good agreement is found to be achieved. [ABSTRACT FROM AUTHOR]

This study reviews recent advancements in solar energy technologies, focusing on enhancing the efficiency of photovoltaic systems. Key research areas include optimizing material properties, improving charge separation, and addressing sustainability challenges. This study identifies critical challenges in quantum dot solar cell technology, such as modeling spectral absorption, managing thermal losses, and evaluating long-term stability. Overall, these innovations represent significant strides toward more efficient and environmentally friendly solar energy solutions. This Review article offers a thorough investigation of the direct current parameters in photovoltaic panels, aiming to boost their efficiency and cost-effectiveness in production. This study underscores the importance of precise modeling and identification of solar cell parameters to more effectively harness solar energy, thereby underscoring its potential for enhancing energy capacity and environmental conservation. Our research includes experimental data on polycrystalline silicon solar cells and simulation results of both individual and polycrystalline cells conducted using the NI Multisim simulator. The focal points of this study encompass the efficient use of solar energy, the pivotal role of silicon as a semiconductor material, and novel methods for augmenting photovoltaic cell efficiency, such as employing nanowires and multilayer semiconductors. This Review Article also examines the effect of temperature on solar cell efficiency and addresses both the theoretical and practical measures of key photovoltaic parameters, including short-circuit current, open-circuit voltage, fill factor, and conversion efficiency. [ABSTRACT FROM AUTHOR]

Light polarization control is a target in photonics, and this paper provides a comprehensive review of research from various groups on the silicon‐on‐insulator (SOI) platform. It draws comparisons between devices such as polarization splitters (PS), polarizers, and polarization splitters/rotators (PSR). These devices are fabricated using various technologies, including silicon nanowires, ridge waveguides, hybrid plasmonic waveguides, and subwavelength grating (SWG) waveguides. A detailed review of polarizers used as cleanup filters in splitters is initiated. Subsequently, various polarization splitters utilizing asymmetric directional couplers (ADCs), which typically exhibiting low extinction ratios (ERs), are delved. To enhance ERs, a detailed comparison of methods outlined in the literature is provided. One notable method includes integrating on‐chip polarizers at both ports to eliminate unwanted light fractions and achieve exceptionally high ERs. Furthermore, SWG‐based polarizers and splitters commonly face issues with Bragg reflections that can affect other photonic devices and lasers and ways to minimize unwanted polarization back reflections in SWG‐designed polarization control devices are examined. Finally, emerging applications in mid‐infrared (MIR) sensing are explored, highlighting the necessity of polarization rotators for on‐chip transverse electric (TE) operation, since quantum cascade lasers, the primary sources in this range, emitting radiation in the (TM) mode. [ABSTRACT FROM AUTHOR]

This study reports the findings from an investigation into charge carrier transport within a silicon nanowire layer. The samples were prepared using the metal-assisted chemical etching method applied to crystalline silicon wafers with a resistance of 10–20 Ω·cm. The resulting silicon nanowires had a diameter of about 100 nm with a resistance of approximately 15 kΩ·cm. Electrical conductivity measurements were performed in both planar and sandwich configurations, revealing analogous conductivity mechanisms across different geometries. Frequency-dependent conductivity studies unveiled the presence of hopping conductivity. A hypothesis is proposed regarding the existence of a potential barrier at the interface between the nanowire layer and the substrate. [ABSTRACT FROM AUTHOR]

Metallic nanowires, particularly polyol-grown silver nanowires, exhibit a morphological instability at temperatures significantly lower than their bulk melting point. This instability is commonly named after Rayleigh's description of the morphological instability of liquid jets, even though it has been shown that its quantitative predictions are not consistent with experimental measurements. In 1996, McCallum et al. proposed a description of the phenomenon assuming a solid wire lying on a substrate. It is assumed that the latter description depicts more accurately the reality. Nanowires with varying diameters have been deposited on silicon wafers. Statistical analysis of their radius and the wavelength of their periodical instability have been performed. McCallum et al.'s model better aligns with experimental observations compared to Rayleigh's description. This validation provides a robust theoretical framework for enhancing the stability of nanowires, addressing a crucial aspect of their development. [ABSTRACT FROM AUTHOR]

Silicon, with its many advantages, is gaining attention in the field of lithium-ion battery anode materials. However, severe volume swelling, poor conductivity, and slow Li+ diffusion kinetics are major obstacles to enhancing the electrochemical properties of silicon anodes. One-dimensional silicon nanowires with a high aspect ratio can effectively ameliorate these issues, while the complexity of the synthesis method limits its development. Here, a three-dimensional flexible electrode of binary-phase Ni-silicide foam loaded with silicon nanowires (NixSiy@Si NWs) was constructed in two simple steps: preparation of metal catalyst nanoparticles using a chemical plating approach and production of silicon nanowires by the supercritical fluid-liquid–solid mechanism. Benefiting from the excellent anchoring ability and superior electrical conductivity of NixSiy as well as the extra space and favorable Li+ and electrolyte diffusion paths provided by the Si NWs network, the as-obtained anode exhibits a high initial Coulombic efficiency of 77% at 0.5 A g−1, excellent cycling performance (a reversible capacity of 1238 mAh g−1 after 200 cycles) and outstanding rate capability (2675, 2497, 2164, 1740, and 1222 mAh g−1 at 0.5, 1, 2, 4, and 8 A g−1, respectively). [ABSTRACT FROM AUTHOR]

Silicon nanowires (SiNWs) are extensively studied in the scientific community due to their remarkable electrical and optical properties. In our previous studies, we have demonstrated that cylindrical−shaped SiNWs sustain longitudinal plasmon resonances (LPRs) and transverse plasmon resonances (TPRs). In this work, we will present the results of our investigation on conical SiNWs with different lengths and demonstrate that the NW size plays a role on the spectral response. We selected two groups of SiNWs with approximately 300 nm and 750 nm in length with different lengths and diameters. We investigated the optical properties of the SiNWs at a high energy and spatial resolution by using transmission electron microscopy and in situ electron energy loss spectroscopy. In the UV region of the spectrum investigated here, the experimental evidence suggests the presence of LPRs and a clear presence of TPRs. We found that, as the NW length increases, the LPR fundamental mode shifts towards higher energies, while the diameter seems to affect the TPR, shifting it to lower energy levels when the diameter increases. These SiNWs can play a role in the development of low−dimensional devices for applications in nano−electronics and nano−photonics. [ABSTRACT FROM AUTHOR]

Metal-assisted catalyzed etching (MACE) technology is convenient and efficient for fabricating large-area silicon nanowires at room temperature. However, the mechanism requires further exploration, particularly the dynamic effect of various ions in the acid-etching solution. This paper investigated the MACE of silicon wafers predeposited with metal nanofilms in an HF-M(NO3)x-H2O etching solution (where M(NO3)x is the nitrate of the fourth-period elements of the periodic table). The oxidizing ability of Fe3+ and NO3− was demonstrated, and the dynamic influence of metal ions on the etching process was discussed. The results show that the MACE of silicon can be realized in various HF-M(NO3)x-H2O etching solutions, such as KNO3, Al(NO3)3, Cr(NO3)3, Mn(NO3)2, Ni(NO3)2, Co(NO3)2, HNO3, and Ca(NO3)2. It is confirmed that the concentration and type of cations in the etching solution affect the etching rate and morphology of silicon. Fe3+ and NO3− act as oxidants in catalytic etching. The fastest etching rate is about 5~6 μm/h in Ni(NO3)2, Co(NO3)2, and Ca(NO3)2 etching solutions. However, a high concentration of K+ hinders silicon etching. This study expands the application of MACE etching solution systems. [ABSTRACT FROM AUTHOR]

InAs nanowires (NWs) were grown on SiOx pinholes formed on Si(111) substrates by molecular beam epitaxy. Influences of electron-beam (EB) irradiation on the SiOx layer on the pinhole formation and the subsequent InAs NW growth were studied. As the EB irradiation dose increased, the pinhole density in the SiOx layer decreased. From atomic force microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy results, it was found that the pinhole etching of the SiOx layer by Ga droplets was suppressed by carbon adsorption due to the EB irradiation. By forming high-density pinholes on the SiOx layer without the EB irradiation, high-density InAs NWs with 1–2 × 1010 cm−2 were grown successfully, and the uniformity in the NW diameter improved. The standard deviation of the NW diameter was 1.8 nm (8.8%) for high-density NWs. In addition, the NW diameter decreased with decreasing EB dose, and the NW diameter was controlled by adjusting the diameter of Ga droplets forming the pinholes. As the NW diameter decreased, photoluminescence spectra of the NWs shifted to higher energies than the bandgap energy of the wurtzite InAs bulk. From these results, we successfully fabricated high-density and high-uniformity InAs NWs with quantum size effects on EB-unirradiated SiOx/Si(111). [ABSTRACT FROM AUTHOR]

Epitaxial BaTiO3 integrated on Si or Si-on-insulator using off-axis radio frequency sputtering is a promising material platform for building electro-optic modulators based on the Pockels effect. Barium titanate thin films with c-axis orientation have been epitaxially integrated on silicon-on-insulator wafers. They exhibit excellent structural quality with Pockels coefficient (r33) > 130 pm/V and propagation loss <2 dB/cm. Our results show that off-axis sputtered BaTiO3 films yield electro-optic modulation similar to that of high-quality films grown by molecular beam epitaxy and that the material is suitable for implementation of low-power Mach–Zehnder interferometer electro-optic modulators integrated on silicon in a Z-cut configuration. [ABSTRACT FROM AUTHOR]

In the present study, we present a unique sensing platform relies on a silicon nanowire (SiNW) and reduced graphene oxide (rGO) hybrid nanostructure capped with (3-aminopropyl) triethoxysilane (APTES) and polyethylene glycol gold nanoparticle (PEG-AuNPs). Herein, MACE technique was applied to synthesize SiNWs, which was then used to develop a sandwich hybrid nanostructure by casting of rGO/APTES/PEG-AuNPs on its surface under room temperature and was characterised using various techniques. The developed PEG-AuNPs/rGO@APTES/SiNWs hybrid nanostructure-based sensing platform was used to detect two types of arsenic, that is, arsenite (As3+) and arsenate (As5+) using cyclic voltammetry in a sensitive and selective manner wherein the presence of arsenic species in real sample (blood) as well as standard samples was recorded. [ABSTRACT FROM AUTHOR]

Semiconductor industry is experiencing unprecedented growth, still driven by Moore's law, which is continually delivering devices with improved performance at lower costs. The continuation of this development places the industry in a divergent trade-off between economic attractiveness, technological feasibility, and the need for further performance improvement. Since the mainstream semiconductor technologies are silicon-based, new disruptive innovations are needed to gain additional performance margins. The use of nanowires is the preferred approach for preserving electrostatic control in the MOS transistor channel, and the application of mechanical stress is a booster of carrier mobility. It is in this context that this paper presents the design, fabrication, theoretical modeling, and characterization of a measurement platform to characterize the mechanical tensile stress of extremely narrow Si nanowires as small as 14.2 ± 1.12 nm in width. The proposed measurement platform enables a precise control of uniaxial strain, in terms of both amplitude and location, through the implementation of a stoichiometric Si3N4 pulling strand exerting a high tensile force on silicon nanowires. Reported devices are fabricated using a silicon-on-insulator wafer with fully complementary metal–oxide–semiconductor-compatible processing and top-down approach. It is observed that the mechanical strength of nanostructured Si is size-dependent and increases with miniaturization. Characterization revealed a record tensile strength value of 7.53 ± 0.8% (12.73 ± 1.35 GPa) for the narrowest nanowires fabricated using a top-down approach. [ABSTRACT FROM AUTHOR]

Nanostructured silicon solar cells are designed to minimize costs through reduced material usage while enhancing power conversion efficiency via superior light trapping and shorter charge separation distances compared to traditional planar cells. This study identifies the optimal conditions for nanoimprinted silicon nanowire (SiNW) solar cells to achieve maximum efficiency under low sunlight concentration and evaluates their performance as bottom cells in III-V multijunction solar cell systems. The findings indicate that the SiNW solar cell reaches its peak performance at a concentration factor of 7.5 suns and a temperature of 40°C or lower. Specifically, the absolute conversion efficiency under these conditions is 1.05% higher than that under unconcentrated light. Compared to a planar silicon solar cell under identical conditions, the SiNW solar cell exhibits a 3.75% increase in conversion efficiency. Additionally, the SiNW single-junction solar cell, when integrated in series with a commercial latticematched InGaP/GaAs dual-junction solar cell, was tested under unconcentrated sunlight, specifically at one-sun, global air mass 1.5 condition, to assess its viability in one-sun multi-junction solar cell applications. The results suggest that a III-V upper subcell with a smaller active area than that of the SiNW subcell is optimal for maximizing current production, which is favorable to the cost reduction of the device. This hybrid configuration is particularly advantageous for terrestrial applications, such as electric vehicles, which demand lightweight, highperformance multijunction solar cell devices. Although the weight reduction of the characterized SiNW solar cell with a full silicon substrate compared to its planar solar cell counterpart is 1.8%, recommendations to increase this reduction to as much as 64.5% are discussed to conclude this paper. [ABSTRACT FROM AUTHOR]

Recently it is shown that sensitivity of biosensors can be considerably improved using single trap phenomena resulting in two‐level random telegraph signal (RTS) switching in current. To develop the transistor structure with a predefined trap position using gold antenna is suggested, which can be excited by light of different intensities to influence the properties of the underlying dielectric layer. High‐quality liquid gate‐all‐around (LGAA) silicon nanowire (NW) field‐effect transistor (FET) biosensors are fabricated with a gold bowtie antenna. The transport and noise properties of these new NW FETs are investigated at 940 nm LED excitation in a 1 mm phosphate‐buffered saline (PBS) solution with pH = 7.4. A strong sensitivity of I–V and noise characteristics is revealed with an increase in LED intensity. Well‐resolved Lorentzian components are only found under the influence of light excitation. A two‐level RTS is successfully excited with linear dependence of its amplitude versus intensity. In addition, repeatable fluctuations in current are resolved as small peaks in I–V curves under infrared illumination, thus confirming the excitation of a two‐level RTS in the biosensors. The results demonstrate that the FET devices with a gold antenna have significant potential for the excitation of two‐level signals to enhance the sensitivity of biosensors. [ABSTRACT FROM AUTHOR]