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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]

Multi-gate field effect transistors (FETs) based on silicon-on-insulator have been popular for several decades due to their improved electrostatic control of the channel current between the source and the drain. Chemical sensors based on such multi-gate FET platform can leverage this improved electrostatic control to detect gases at very low concentration with ultrahigh sensitivity. Electrostatically formed nanowire (EFN) is a multiple-gate FET device which has proven to be an excellent platform for detecting volatile organic compounds and gases. In case of such multi-gate FET sensors, it is imperative to rigorously understand the influence of each gate in controlling the sensing performances. Using palladium nanoparticles decorated EFN (Pd-EFN) as an example, the current work presents a detailed methodology for determining the operating parameters for maximal sensing performances of the Pd-EFN sensor towards hydrogen sensing. We observed that a single operating point does not yield best results with regard to sensor response, dynamic range, and power efficiency. By optimizing the operating points (by varying the different gate biases), a sensor response of 107% was reached even at low concentrations of hydrogen (500 ppm) which is significantly lower than the lower explosive limit of 4% and a tunable dynamic range over three decades (4–8000 ppm) was obtained. Also, the sensor response was not compromised at low driving voltages (100 mV) thus contributing to low power consumption of the sensor. Such a correlation between the working point of the transistor and the various sensor performance metrics (maximum sensor response, dynamic range etc) has not been studied before to the best of our knowledge and this study can be extended to EFN for other gases and any other multi-gate FET sensors (not limited to Si based sensors). This study can pave the way for effective design of future multi-gate transistors for gas sensing. [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]

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]

This study presents the numerical modeling of an underlap gate cavity-integrated reconfigurable silicon nanowire Schottky barrier transistor (UGC-RSiNW SBT) that features a gate-drain underlap region, specifically designed for biosensing applications. The proposed device features a cavity under the control gate on the source side, allowing the immobilization of neutral and charged biomolecules having different dielectric constants. The program gate is specifically placed over the channel-drain Schottky junction to reduce the ambipolar behavior of the device. Using the 2D Poisson equation, we model electrostatic characteristics such as electric potential, threshold voltage, electric field, and drain current. Biomolecules in a cavity can be detected and identified by measuring the variation in threshold voltage ( V Th ), which is caused by the biomolecules' interactions with the local electric field and their influence on charge carrier transport. Simulation results using Silvaco TCAD tools demonstrate significant improvements in sensitivity of the proposed biosensor as compared to conventional RFET biosensors. The study shows a 97.91% increase in the V Th sensitivity of the device for the N-channel and a 16% improvement for the P-channel. The drain current sensitivity and the linearity of proposed biosensor is enhanced upto the values of 2792 and 0.997 respectively in n-mode configuration whereas in p-mode configuration, the drain current sensitivity and the linearity comes out to be 968 and 0.995 respectively. These high sensitivity and linearity values make this biosensor superior to the existing state-of-the-art biosensors. The simulated results were validated when compared with existing literature, confirming the effectiveness of the Silvaco TCAD tool in accurately modeling the biosensor's performance These findings offer valuable insights for developing highly sensitive biosensors for healthcare and biotechnology applications. [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]

The main goal of this research is the development of a label-free biosensor for the detection of diabetes mellitus (DM) using the target molecule retinol-binding protein 4 (RBP4). The enzyme-linked immunosorbent assay (ELISA) approach, currently used to detect DM, is time-consuming and difficult. As a result, label-free biosensors are being considered as an alternative. In this research, silicon nanowires (SiNWs) were selected as the transducer for this biosensor due to their low cost, real-time analysis capability, high sensitivity, and low detection limit. The SiNWs were created using conventional lithography, reactive ion etching (RIE), and physical vapor deposition (PVD), and then dripped with a gold nanoparticle solution to create gold-decorated SiNWs. The surface of the golddecorated SiNWs was functionalized using 3-aminothiophenol and glutaraldehyde solutions before being immobilized with DM RBP4 antibodies and targets. The electrical characterization of the gold nanoparticle decorated SiNWs biosensor revealed good performance in DM detection. The pH tests confirmed that the SiNWs acted as a transducer, with current proportional to the DM RBP4 concentration. The estimated limit of detection (LOD) and sensitivity for detecting DM RBP4 binding were 0.076 fg/mL and 8.92 nA(g/mL)-1, respectively. This gold nanoparticle decorated SiNWs biosensor performed better than other methods and enabled efficient, accurate, and direct detection of DM. The SiNWs could be used as a distinctive electrical protein biosensor for biological diagnostic purposes. In conclusion, gold nanoparticle deposition offers effective label-free, direct, and high-accuracy DM detection, outperforming previous approaches. Thus, these SiNWs serve as novel electrical protein biosensors for future biological diagnostic applications. [ABSTRACT FROM AUTHOR]

This paper presents an integrated approach for a retinal prosthesis that overcomes the scalability challenges and limitations of conventional systems that use external cameras. Silicon nanowires (SiNWs) are utilized as photonic sensors due to their nanoscale dimensions and high surface-to-volume ratio. To enhance these properties and achieve high photoresponsivity, our research team developed a vertically stacked SiNW structure using a fabrication method entirely based on dry etching. The fabricated SiNW photodetector demonstrated excellent electrical and optical characteristics, including linear I–V characteristics that confirmed ohmic contact formation and high photoresponsivity exceeding 105 A/W across the 400–800 nm wavelength range. The SiNW photodetector, following its integration with a switched capacitor stimulator circuit, exhibited a proportional increase in stimulation current in response to higher light intensity and increased SiNW density. In vitro experiments confirmed the efficacy of the integrated system in inducing neural responses from retinal cells, as indicated by an increased number of neural spikes observed at higher light intensities and SiNW densities. This study contributes to sensor technology by demonstrating an approach to integrating nanostructures and electronic components, which enhances control and functionality. [ABSTRACT FROM AUTHOR]

Purpose: Field-effect transistor (FET) has excellent electronic properties and inherent signal amplification, and with the development of nanomaterials technology, FET biosensors with nanomaterials as channels play an important role in the field of heavy metal ion detection. This paper aims to review the research progress of silicon nanowire, graphene and carbon nanotube field-effect tube biosensors for heavy metal ion detection, so as to provide technical support and practical experience for the application and promotion of FET. Design/methodology/approach: The article introduces the structure and principle of three kinds of FET with three kinds of nanomaterials, namely, silicon nanowires, graphene and carbon nanotubes, as the channels, and lists examples of the detection of common heavy metal ions by the three kinds of FET sensors in recent years. The article focuses on the advantages and disadvantages of the three sensors, puts forward measures to improve the performance of the FET and looks forward to its future development direction. Findings: Compared with conventional instrumental analytical methods, FETs prepared using nanomaterials as channels have the advantages of fast response speed, high sensitivity and good selectivity, among which the diversified processing methods of graphene, the multi-heavy metal ions detection of silicon nanowires and the very low detection limit and wider detection range of carbon nanotubes have made them one of the most promising detection tools in the field of heavy metal ions detection. Of course, through in-depth analysis, this type of sensor has certain limitations, such as high cost and strict process requirements, which are yet to be solved. Originality/value: This paper elaborates on the detection principle and classification of field-effect tube, investigates and researches the application status of three kinds of FET biosensors in the detection of common heavy metal ions. By comparing the advantages and disadvantages of each of the three sensors in practical applications, the paper focuses on the feasibility of improvement measures, looks forward to the development trend in the field of heavy metal detection and ultimately promotes the application of field-effect tube development technology to continue to progress, so that its performance continues to improve and the application field is constantly expanding. [ABSTRACT FROM AUTHOR]

This study investigates the fabrication and characterization of an innovative nanoelectromechanical system force sensor that utilizes suspended submicron silicon nanowires for detecting multi‐axis forces in the micro‐newton range. The sensor combines microscale shuttle platforms with nanowire piezoresistors along with retaining springs. Its fabrication involves a rather involved set of Si deep etching, doping, metallization, release, and encapsulation processes on silicon‐on‐insulator wafers. Electromechanical characterization demonstrates sensor reliability under mechanical strains up to the level of 10% as well as gauge factor measurements. Dynamic response analysis confirms a high resonant frequency of 12.34 MHz with a quality factor of 700 in air, closely matching simulation results. Thermal characterization of the sensor reveals a Temperature Coefficient of Resistance of 6.4 × 10⁻⁴ °C⁻¹. Sensor characterization under jet flow reveals its ability to detect strong flows demonstrating a resistance change of as much as 2.02% under sustained gas flow through a nozzle. Sensor integration into the gas flow measurement setup demonstrates its versatility in detecting small forces, paving the way for further exploration of thermomechanical factors. Combined with its miniature footprint, the sensor's electromechanical performance hints at applications in the analysis of velocity gradients in microscale flows including micro/nano diffusers and nozzles in small satellite propulsion. [ABSTRACT FROM AUTHOR]

The present work deals with the study of the effect of temperature on the Raman spectroscopy and electrical properties of the silicon nanowires. The nanowires are fabricated through silver assisted electrochemical etching process. Prior to these studies, the fabricated nanowires are characterized through field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), and X-ray diffraction (XRD) measurements. FESEM reveals the vertical alignment of the nanowires. FETEM indicates the materials to be highly crystalline, which is also complemented by the XRD result. Raman peak is blue-shifted with a decrease of temperature suggesting lattice disturbance at low temperature. Temperature-dependent current-voltage (I-V) measurements are fitted with Cheung’s model and the characteristic parameters viz. ideality factor (n), barrier height (ϕb), and series resistance (Rs) are estimated from the fitted plots. At lower temperatures, the value of n highly deviates from the ideal value of unity and is 23.42 at 110 K. The materials are observed to obey space charge limited conduction (SCLC) to trap charge limit current (TCLC) with increasing bias at lower temperatures. [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.

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 lattice-matched 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, high-performance 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.

Surface functionalization of 1D materials such as silicon nanowires is a critical preparation technology for biochemical sensing. However, existing nonselective functionalization techniques result in nonlocal binding and contamination, with potential device damage risks. Associated risks are further exacerbated for next-generation devices of a 3D nature with challenging topographies. Such 3D devices draw inspiration from the out-of-plane evolution of planar transistors to FinFETs and to today's gate-all-around transistors. This study is the first reported technological work addressing stencil-based surface decoration and selective functionalization of a suspended silicon nanowire building block embedded within such a device that involves two-order-of-magnitude thicker features compared to the nanowire critical dimensions. A gold pattern resolution of 3.0 μm atop the silicon nanowires is achieved with a stencil aperture critical dimension of 2.2 μm, accompanied by a die-level registration accuracy of 1.2 ± 0.3 μm. Plasma-enhanced chemical vapor deposition-based silicon nitride stencil membranes as large as 300 × 300 μm2 are used to define the apertures without any membrane fracture during fabrication and membrane cleaning. The pattern-blurring aspect as a resolution-limiting factor is assessed by using 24 individual nanowire devices. Finally, gold-patterned silicon nanowires are functionalized using thiolated heparin and employed for selective attachment and detection of the human recombinant basic fibroblast growth factor (FGF-2). With the potential involvement in angiogenesis, the process of new blood vessel formation crucial for tumor growth, FGF-2 can serve as a potential prognostic biomarker in oncology. Demonstrated selectively on nanowires with high pattern resolution, the proposed functionalization approach offers possibilities for parallel sensing using vast nanowire arrays embedded in 3D device architectures developed for next-generation biochemical sensors in addition to serving various encapsulation and packaging needs. [ABSTRACT FROM AUTHOR]

Combined with other materials and device improvements, Si anodes can provide a step change in Lithium‐ion battery properties, enabling cell energy density to exceed 400 Wh kg−1. Freestanding, large‐area anodes of 100% Si produced by a slurry‐free method without carbon or binders are introduced. Their structure, a dense network of interconnected high aspect ratio Si nanowires (Si NWs), is analogous to a nanotextile and provides handling like paper. In conventional liquid electrolytes, the anode capacity is 2500 mAh g−1 at high mass loadings (e.g., 6.6 mAh cm−2), and cycling stability is 76% after 200 deep cycles, and 100% after 1800 cycles when cycled at 1000 mAh g−1. The nanowire network structure reduces junction resistance between particles and prevents any pulverization upon cycling. Combined impedance and composition‐selective electron microscopy demonstrate that capacity fading is exclusively through the progressive increase of SEI thickness and resistance. Full cell capacity with NMC811 translates into an energy density of 420 Wh kg−1 at the true cell level. [ABSTRACT FROM AUTHOR]

In this paper, for the first time, we have investigated a Spacer-Engineered Reconfigurable Silicon Nanowire Schottky Barrier Transistor (SE R-Si NW SBT) as a label-free Biosensor. The SE R-Si NW SBT works as N and P-channel by applying appropriate bias on dual gates (control gate and program gate) employed near source and drain (S/D) side, respectively. The biomolecules are immobilized in the region between the control and program gates on thin silicon dioxide layer. The presence of biomolecules effectively modulates the Schottky tunneling width at the S/D and channel potential profile. Calibrated results show that the SE R-Si NW SBT biosensor is capable of detecting dual polarity biomolecules with high sensitivity, selectivity, and linearity. The performance of the SE R-Si NW SBT biosensor is compared with the Conventional Reconfigurable FET (C-RFET) biosensor. Also, the possible fabrication flow of the SE R-Si NW SBT biosensor is presented. Furthermore, the sensitivity and linearity parameters are compared with the state-of-art FET-based biosensors. The promising results of the SE R-Si NW SBT biosensor suggest its potential for label-free biosensing applications, as it offers improved sensitivity, selectivity, and linearity in biosensing applications. [ABSTRACT FROM AUTHOR]

Over the last two decades, silicon nanowire field-effect transistors (SiNW-FETs) with prominent merits of high surface-to-volume ratio, excellent biocompatibility and mature fabrication with standard silicon technology, have been widely studied as ultrahigh sensitive biosensors for the detection of target biomolecules, such as proteins, nucleic acids, cells and viruses so on. Herein we present a comprehensive review of the fundamental aspects of SiNW-FET biosensors, involving the working principle and the device fabrication, surface functionalization, and system integration with fluid exchange and electrical detection. Futhermore, we emphatically discuss the electrical detection of cardiac-specific biomarkers related to acute myocardial infarction disease. SiNW-FET biosensors are being increasingly exploited as promising diagnostic devices, which provide high sensitivity, high integration density, high speed sampling, strong specificity, and real-time and label-free detection for simple and cheap clinical testing. [ABSTRACT FROM AUTHOR]

This paper presents an integrated approach for a retinal prosthesis that overcomes the scalability challenges and limitations of conventional systems that use external cameras. Silicon nanowires (SiNWs) are utilized as photonic sensors due to their nanoscale dimensions and high surface-to-volume ratio. To enhance these properties and achieve high photoresponsivity, our research team developed a vertically stacked SiNW structure using a fabrication method entirely based on dry etching. The fabricated SiNW photodetector demonstrated excellent electrical and optical characteristics, including linear I–V characteristics that confirmed ohmic contact formation and high photoresponsivity exceeding 105 A/W across the 400–800 nm wavelength range. The SiNW photodetector, following its integration with a switched capacitor stimulator circuit, exhibited a proportional increase in stimulation current in response to higher light intensity and increased SiNW density. In vitro experiments confirmed the efficacy of the integrated system in inducing neural responses from retinal cells, as indicated by an increased number of neural spikes observed at higher light intensities and SiNW densities. This study contributes to sensor technology by demonstrating an approach to integrating nanostructures and electronic components, which enhances control and functionality.

Silicon nanowires (SiNWs) are emerging as versatile components in the fabrication of sensors for implantable medical devices because of their exceptional electrical, optical, and mechanical properties. This paper presents a novel top-down fabrication method for vertically stacked SiNWs, eliminating the need for wet oxidation, wet etching, and nanolithography. The integration of these SiNWs into body channel communication (BCC) circuits was also explored. The fabricated SiNWs were confirmed to be capable of forming arrays with multiple layers and rows. The SiNW-based pH sensors demonstrated a robust response to pH changes, and when tested with BCC circuits, they showed that it was possible to quantize based on pH when transmitting data through the human body. This study successfully developed a novel method for SiNW fabrication and integration into BCC circuits, which could lead to improvements in the reliability and efficiency of implantable medical sensors. The findings demonstrate significant potential for bioelectronic applications and real-time biochemical monitoring. [ABSTRACT FROM AUTHOR]

The miniaturization and higher power density of modern electronics pose a significant challenge in thermal management. A key focus in addressing this challenge revolves around the advancement of thermal interfaces within microchip packaging, aiming to enhance thermal energy dissipation and optimization of performance. Copper nanowires are extensively employed in the chip industry as interconnects for signal transmission and thermal management purposes. Investigating the impact of reduced cross-section on the thermal transport properties of nanowires is crucial. In this study, the thermal conductivity of copper and silicon nanowires is studied with variations in the length of the nanowires. The simulation is conducted with the Equilibrium Molecular Dynamics (EMD) process. The cross-section of the nanowire is kept fixed (10 × 10 nm) and with the increase in length, its thermal conductivity is studied. At room temperature for a 50 nm length, the lattice thermal conductivity value is 1.68 and 0.037 W m − 1 K − 1 for silicon and copper nanowires, respectively. We further studied the phonon scattering, mean free path, and group velocity of silicon and copper lattices. Our study may help to design more thermally efficient microchips and innovate new cooling methods of microelectronics. [ABSTRACT FROM AUTHOR]

We present the design of a H2 gas sensor based on palladium (Pd) decorated silicon-on-insulator (SOI) nanowire field effect transistor (FET) with a standard SOI complementary metal-oxide-semiconductor fabrication process, where a top Pd layer plays a dual role of a catalyst and a surrounding metal gate. A numerical study was conducted based on a simplified steady-state model to describe the sensing mechanism of H2 in dry air at 300 K. The simulation is based on the model of dissociative H2 adsorption on the Pd surface and the formation of a dipole layer at the Pd/SiO2 interface. The H atoms induced dipoles lead to a potential drop which exponentially increases the FET drain current and consequently, the sensor response. The FET drain current is controlled by its back-gate bias and by varying the H2 concentrations; it is shown that the drain current response reaches 1.8 × 108% for 0.8% H2 in air and a superior sensitivity of 4.58 × 104%/ppm in the sub-threshold operation regime. The sensor exhibits an outstanding theoretical detection limit of 50 ppt (response of 1%) and an upper dynamic range limit of 7000 ppm which allow for timely and accurate detection of H2 gas presence. The power consumption ranges between ∼10 fW (dry air) to ∼20 nW (0.8% H2 in dry air) and therefore paves the way for a very large-scale integration commercial sensing platform. [ABSTRACT FROM AUTHOR]

This paper introduces a new design of silicon nanowire (Si NW) phototransistor (PT) arrays conceived explicitly for improved CMOS image sensor performance, and comprehensive numerical investigations clarify the characteristics of the proposed devices. Each unit within this array architecture features a top-layer vertical Si NW optimized for the maximal absorption of incoming light across the visible spectrum. This absorbed light generates carriers, efficiently injected into the emitter–base junction of an underlying npn bipolar junction transistor (BJT). This process induces proficient amplification of the output collector current. By meticulously adjusting the diameters of the NWs, the PTs are tailored to exhibit distinct absorption characteristics, thus delineating the visible spectrum's blue, green, and red regions. This specialization ensures enriched color fidelity, a sought-after trait in imaging devices. Notably, the synergetic combination of the Si NW and the BJT augments the electrical response under illumination, boasting a quantum efficiency exceeding 10. In addition, by refining parameters like the height of the NW and gradient doping depth, the proposed PTs deliver enhanced color purity and amplified output currents. [ABSTRACT FROM AUTHOR]

Silicon nanowires entail significant potential as sensors in nanoelectromechanical systems. Despite its crucial impact in such applications, inconsistent trends in mechanical behavior reported in computational and experimental studies remain unexplained. Hence, scale effect in even the most fundamental elastic properties requires clarification. This work introduces a multiscale model to bridge the existing gap between atomistic simulations and experimental observations encountered around a critical dimension of 10 nm. The combined approach of this work is based on molecular dynamics and modified core–shell model and captures the scale effect over a substantial size range. The evolution of the modulus of elasticity is thus studied and linked to nanowire critical dimension through the parameterization of surface inhomogeneity. The developed method is also validated through an analysis of native oxide revealing an average modulus of elasticity of 75 GPa. The method’s applicability can be extended to similar one-dimensional structures with unique surface states.

Determining the electron field emission (FE) turn-on field of the silicon nanowires(SiNWs) array can better adapt to the application of field-assisted photocathode. Here, we report the observations of FE from SiNWs grown on n-type Si(100) by utilizing silver induce chemical etching (SICE) approach. The growth of SiNWs is confirmed by XPS and XRD spectra and the optical band gaps, studied from the Kubelka-Munk function reveals the red shifting behavior. The grown SiNWs show an excellent FE property. The new proposed analytical framework enables one to understand the FE properties in better sense as compared to the conventional utilized framework, named as Fowler-Nordhiem (F-N) approach. It improves the analysis by introducing a new parameter i.e. boost-factor to take care of the FE data in totality unlike the traditional framework, where only currents were considered for higher electric fields. Moreover, it also addresses the ambiguity present in the previously used approach. A quantum mechanical model is adopted to explain the improved FE properties from these NWs by using the concept of tunneling probability. These results can enrich our knowledge on the FE of SiNWs and are highly related to the development of the next-generation of Si nano-electronic devices. [ABSTRACT FROM AUTHOR]

Highly sensitive and specific detection of dimethyl methylphosphonate (DMMP), a typical sarin simulant, was demonstrated by silicon nanowire (SiNW) array sensor. The SiNW array devices were fabricated by conventional microfabrication methods and self-assembled with the sensitive material bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane to obtain unique sensitivity to the DMMP vapor. Effect of surface functionalization parameters on DMMP sensing was optimized to increase the adsorption site number density for specific binding of DMMP. The optimized SiNW array sensor showed a high sensitivity to DMMP vapor in a detection limit of 0.2 ppm. Role of the SiNWs array is proposed to possess an extremely large surface area for a hydrogen bond-mediated recognition of the P = O group in DMMP. These initial promising results offer an alternative tool for fabrication and modification of highly sensitive, reliable and low-cost SiNW sensors to detect DMMP. [ABSTRACT FROM AUTHOR]

We report silicon nanowire (SiNW) growth with a novel Cu-In bimetallic catalyst using a plasma-enhanced chemical vapor deposition (PECVD) method. We study the structure of the catalyst nanoparticles (NPs) throughout a two-step process that includes a hydrogen plasma pre-treatment at 200 °C and the SiNW growth itself in a hydrogen-silane plasma at 420 °C. We show that the H2-plasma induces a coalescence of the Cu-rich cores of as-deposited thermally evaporated NPs that does not occur when the same annealing is applied without plasma. The SiNW growth process at 420 °C induces a phase transformation of the catalyst cores to Cu7In3; while a hydrogen plasma treatment at 420 °C without silane can lead to the formation of the Cu11In9 phase. In situ transmission electron microscopy experiments show that the SiNWs synthesis with Cu-In bimetallic catalyst NPs follows an essentially vapor-solid–solid process. By adjusting the catalyst composition, we manage to obtain small-diameter SiNWs—below 10 nm—among which we observe the metastable hexagonal diamond phase of Si, which is predicted to have a direct bandgap. [ABSTRACT FROM AUTHOR]

There has been huge interest in synthetizing silicon nanomaterials for various applications ranging from electronics to biology due to their attractive properties. For many device applications, it is pivotal to control the morphology and dimensions of silicon-based nanomaterials while considering a continuous demand for higher resolution and large aspect ratio. Such prerequisites concomitant with scalability, reliability, low cost and compatibility with existing manufacturing processes are not trivial to fulfill, bringing a need to develop nanofabrication techniques. In this regard, the work proposed in this paper involves the advancement of a top-down fabrication approach called "Metal-assisted Chemical Etching (MACE)" which has the potential to overcome the current limitations of 1D and 3D semiconductor nanomanufacturing processes. Large-area high density vertical silicon nanowire arrays are fabricated by this technology. Two-dimensional silica colloidal crystal template or laser interference lithography are used to create gold metal nanohole arrays on a silicon substrate, which enables to precisely control the final diameter of the nanowires. The formation of ordered silicon nanowire arrays is due to selective and highly anisotropic etching of silicon induced by the gold patterned mask. [ABSTRACT FROM AUTHOR]

Nanostructures and microstructures are fabricated on silicon surfaces to reduce the reflection and enhance the absorption of light. It can be used to improve infrared (IR) absorption-based MEMS bolometer applications. The cost-effective metal-assisted chemical etching (MACE) method is used to synthesize the silicon nanowires arrays for surface roughness. The fabricated Si nanowires reveal roughly 5 times increment in the full-wave half-maxima (FWHM) of the X-ray rocking curve in comparison to crystalline silicon (c-Si) due to the presence of structural defects on the surface which arises because of the anisotropic chemical etching. Electron microscopy results confirm the formation of nanowires in Omni-directions with tens of nanometre diameter and a few μm lengths. The infrared response of silicon nanowires shows that the broadband infrared absorption is enhanced about 2.5 – 3 times compared to that of polished silicon for the IR range (2.5 – 20 μm). The IR response of the Si nanowires provides promising potential applications as broadband IR absorbing/ sensing material. [ABSTRACT FROM AUTHOR]

Molten salt electrolytic synthesis of silicon is identified as a potential industry method due to its thorough deoxidization of oxide and short-flow synthetic progress. However, figuring out a more efficient and sustainable strategy for the increase of the reduction process as well as the control of product morphology still needs endless research. In this study, benefiting from the high electrical conductivity of metallic silver and the easy separation of silver from silver-silicon alloys during the electrolysis of SiO 2 , metallic silver was introduced to electric-catalyze the production of silicon. Firstly, metallic silver was introduced into the silica matrix by a simple silver mirror reaction. Secondly, the mixed Ag\SiO 2 precursor was located at the cathode for molten salt electrolysis. Finally, silicon nanowires were herein achieved in molten NaCl–CaCl 2. Mechanisms of metal Ag played during the electric-polarization process of silica and the electrochemical nucleation of silicon were further analyzed by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Field-Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectra. The results demonstrate that Ag helps construct Si nanowires via a classic Ag-Si binary alloy-droplet process and provided quantitative guidance for the large-yield production of silicon nanowires via adding 0.08–0.17 g Ag versus 1 g SiO 2 , controlling the temperature at 850–900 °C and electrolysis voltage at 2.6–2.8 V (2.6V at first 1 h and 2.8V at last 5 h). The synthesized silicon nanowires present two types of linear structures based on two three-phase interlines (3PIs) models and a streamed long-straight nanowire is observed. [ABSTRACT FROM AUTHOR]

Challenges in scaling dynamic random-access memory (DRAM) have become a crucial problem for implementing high-density and high-performance memory devices. Feedback field-effect transistors (FBFETs) have great potential to overcome the scaling challenges because of their one-transistor (1T) memory behaviors with a capacitorless structure. Although FBFETs have been studied as 1T memory devices, the reliability in an array must be evaluated. Cell reliability is closely related to device malfunction. Hence, in this study, we propose a 1T DRAM consisting of an FBFET with a p+–n–p–n+ silicon nanowire and investigate the memory operation and disturbance in a 3 × 3 array structure through mixed-mode simulations. The 1T DRAM exhibits a write speed of 2.5 ns, a sense margin of 90 μA/μm, and a retention time of approximately 1 s. Moreover, the energy consumption is 5.0 × 10−15 J/bit for the write '1' operation and 0 J/bit for the hold operation. Furthermore, the 1T DRAM shows nondestructive read characteristics, reliable 3 × 3 array operation without any write disturbance, and feasibility in a massive array with an access time of a few nanoseconds. [ABSTRACT FROM AUTHOR]

The dopingless nanowire (NW) field-effect transistor (FET) has been discovered as a remedy to low drive current problems of junctionless NWFET. To complete the state-of-the-art devices, an improved technique is needed for enhancing the performance of dopingless NWFET. One such structure with improved characteristics of dopingless NWFET is proposed in this paper and termed a dual-material heterodielectric dopingless NWFET (DM-HDNWFET). We demonstrate the performance improvement of the proposed DM-HDNWFET by comparing its results with those of conventional dual-material gate NWFET. Performance improvements, in terms of drive current, transconductance, and transconductance gain factor, are observed for the proposed structure. By incorporating dual-material at the gate and heterodielectric as oxide, this structure paves the way for further enhancing the capabilities of conventional dopingless configurations. The optimization of the proposed structure is also carried out in this study along with in-depth noise analysis. The noise analysis for the proposed structure is carried out by studying parameters like the noise figure (NF), real impedance (Z0), auto-correlation function (ACF), and cross-correlation function, and evaluating their behavior towards variation in the lengths of the high-k dielectric, gate 1, and gate 2. The noise analysis shows the capability of this structure to be used efficiently in communication applications. [ABSTRACT FROM AUTHOR]

Catalytic synthesized ultrathin silicon nanowires (SiNWs) are ideal 1D channel materials to fabricate high‐performance transparent and low‐cost thin film transistors (TFTs) that are widely needed for flexible electronics and displays. In this work, a scalable integration of orderly array of SiNW array, with a uniform diameter of only 52 ± 4 nm, grown directly upon glass/wafer substrates, via a guided in‐plane solid–liquid–solid (IPSLS) process, and passivated by a new solution oxidizing/etching cycling technique is demonstrated. This has enabled an all‐low‐temperature (<350 °C) fabrication of high‐performance SiNW‐TFTs, achieving Ion/Ioff current ratio and subthreshold swing (SS) of >106 and 120 mV dec−1 respectively, with excellent negative and positive bias stabilities. Importantly, the SiNW‐TFTs fabricated on glasses with ITO/or metal electrodes demonstrate a high transparency of 90% or 73% respectively, making them ideal candidates for building the next generation of high aperture displays, transparent electronics, and augmented reality applications. [ABSTRACT FROM AUTHOR]

To address recent energy and environmental issues, such as global warming and resource depletion, significant interest has been shown in carbon dioxide (CO2) fixation based on photoelectrochemical processes under solar light irradiation. The present paper describes the applicability of gold nanoparticles-decorated silicon nanowire arrays (Au/SiNW) as photoelectrodes to promote CO2 reduction. The decoration with Au nanoparticles of SiNW was performed by an electroless plating utilizing surface hydrogen-terminated silicon groups, generated during the nanowire formation process. Au/SiNW exhibits efficient photoelectrochemical performance for CO2 reduction to produce CO selectively in an aqueous medium under simulated solar light irradiation owing to its vertically aligned nanowire structure and Au nanoparticles as cocatalysts. The former provides high specific surface area and light trapping effect, and the latter induces selective interaction with CO2. Moreover, a unique two-steps method for Au decoration that consists of photo-assisted deposition of copper nanoparticles and the following electroless plating to replace Cu atoms to Au ones achieves more uniform decoration of SiNW with highly dispersed core–shell structured Cu@Au nanoparticles. The resulting photoelectrode, termed Cu@Au/SiNW, shows improved selectivity toward CO production and gives a good Faradic efficiency of 72% in an aqueous medium. [ABSTRACT FROM AUTHOR]

This study investigates the modulus of elasticity of silicon nanowires using a combination of molecular dynamics simulations and machine learning techniques. The research presents a substantial dataset with over 3000 data points obtained from molecular dynamics simulations, which reveals detailed insights into the mechanical properties of silicon nanowires and underscores the importance of accurate model calibration. Machine learning surrogate models are employed to predict the elasticity of silicon nanowires, focusing on the influence of surface state and crystal orientation. By analyzing partial dependencies and using inverse pole figures, the study demonstrates that the modulus of elasticity exhibits significant orientation dependence. This work bridges computational and experimental approaches, offering a refined understanding of the mechanical behavior of silicon nanowires. The findings highlight the potential of integrating machine learning with atomistic simulations to improve the predictive accuracy of material properties, building the framework for advancements in nanoelectromechanical applications. [Display omitted] • Integrated atomistic modeling with machine learning for modeling silicon nanowires. • Dataset of 3000+ demonstrated size-dependent mechanical responses in Si NWs. • Studies surface state and crystal orientation impacts on elasticity of Si NWs. • Demonstrates orientation-dependent elasticity in Si NWs through inverse pole figure. • Efficient estimation of modulus of elasticity through meticulous model calibration. [ABSTRACT FROM AUTHOR]

Abstract Catalytic synthesized ultrathin silicon nanowires (SiNWs) are ideal 1D channel materials to fabricate high‐performance transparent and low‐cost thin film transistors (TFTs) that are widely needed for flexible electronics and displays. In this work, a scalable integration of orderly array of SiNW array, with a uniform diameter of only 52 ± 4 nm, grown directly upon glass/wafer substrates, via a guided in‐plane solid–liquid–solid (IPSLS) process, and passivated by a new solution oxidizing/etching cycling technique is demonstrated. This has enabled an all‐low‐temperature (106 and 120 mV dec−1 respectively, with excellent negative and positive bias stabilities. Importantly, the SiNW‐TFTs fabricated on glasses with ITO/or metal electrodes demonstrate a high transparency of 90% or 73% respectively, making them ideal candidates for building the next generation of high aperture displays, transparent electronics, and augmented reality applications.

Accurate monitoring of blood glucose levels is crucial for the diagnosis of diabetes patients. In this paper, we proposed a simple "mixed-catalyzer layer" modified silicon nanowire field-effect transistor biosensor that enabled direct detection of glucose with low-charge in high ionic strength solutions. A stable screening system was established to overcome Debye screening effect by forming a porous biopolymer layer with polyethylene glycol (PEG) modified on the surface of SiNW. The experimental results show that when the optimal ratio (APTMS:silane-PEG = 2:1) modified the surface of silicon nanowires, glucose oxidase can detect glucose in the concentration range of 10 nM to 10 mM. The sensitivity of the biosensor is calculated to be 0.47 μAcm−2mM−1, its fast response time not exceeding 8 s, and the detection limit is up to 10 nM. This glucose sensor has the advantages of high sensitivity, strong specificity and fast real-time response. Therefore, it has a potential clinical application prospect in disease diagnosis. [ABSTRACT FROM AUTHOR]

This paper presents a novel optical sensor that can determine the refractive index of many materials, alloys and fluids. In this method, by using a small silicon wire structure with dimensions of 4 μ m × 0.7 μ m , × 0.3 μ m with two reciprocating walls covered with gold and a vertical window, we will be able to calculate the refractive index of materials at the wavelength of 1.3 µm. The settling time to determine the refractive index of this optical sensor is only 375 fs, so it will be able to record very fast refractive index changes. This sensor is incredibly sensitive even to smallest changes for real and imaginary parts of the refractive index. This sensor presents a new measurement criterion for sensitivity which amounts to S = 145000 and its numerical simulation has been performed by FDTD algorithm. [ABSTRACT FROM AUTHOR]

In order to examine the possibility of developing silicon nanowires (Si NWs) with enhanced mechanical characteristics, this study investigates the effects of fullerene integration on the mechanical characteristics of [110]-oriented Si NWs subjected to uniaxial tension by performing classical molecular dynamics simulations. For this purpose, various types of fullerenes (i.e., C60, C180, and C320) with different weight ratios (i.e., 0.5%, 0.75%, 1.25%, and 2.5%) are randomly embedded into Si NWs with diameters of 3, 4 and 5 nm. It is demonstrated that the tensile strength, the ultimate tensile strain and Young's modulus of fullerene-embedded Si NWs (F-Si NWs) can be enhanced up to 140.74%, 70.59% and 23.13%, respectively. Resistance to lateral contraction and blockage of crack propagation are considerable advantages of fullerenes, which significantly improves the mechanical properties of Si NWs without causing a considerable transition to amorphous phase from the cubic diamond lattice structure of bulk silicon. Furthermore, while additive-free Si NW with a diameter of 5 nm showing brittle failure at room temperature, a ductile behavior is observed at the same loading rate for the fullerene embedded NWs independently from the fullerene types and weight ratios. Considering the outstanding mechanical enhancements and their tunable characteristics, F-Si NWs might reveal promising opportunities for the next generation semiconductors. [ABSTRACT FROM AUTHOR]

In this work, the impact of different substrate-gate voltage bias conditions (below and above the device threshold voltage) on current-voltage characteristics and sensitivity of a silicon nanowire field-effect transistor (SiNW-FET) biosensor was investigated. A 3-dimensional device structure with n-type SiNW channel and a substrate gate electrode was designed and electrically simulated In the Silvaco ATLAS. Next, the SiNW channel was covered with a range of interface charge density to mimic the charged target biomolecule captured by the device. The outcome was translated into a drain current versus interface charge semi-log graph and the device sensitivity was calculated using the linear regression curve's slope of the plotted data. The device's electrical characteristic shown higher generation of output drain current values with the increase of negative substrate-gate voltage bias due to the hole carriers' accumulation that forms a conduction channel in the SiNW. Application of higher negative interface charge density increased the change in drain current, with the device biased with higher substrate-gate voltage shows more significant change in drain current. The device sensitivity increased when biased with higher substrate-gate voltage with highest sensitivity is 75.12 nA/dec at substrate-gate voltage bias of -1.00 V. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate a wafer-scale fabrication of biologically sensitive Si nanowire FET for pH sensing and electrical detection of deoxyribonucleic acid (DNA) hybridization. Based on conventional “top-down” CMOS compatible technology, our bioFETs explore a wide range of design (nanowires (NW), nanoribbons (NR), and honeycomb (HC) structures) with opening access scaled down to only 120 nm. After device fabrication, IDS-VBG transfer and IDS-VDS output characteristics show a conventional n-type FET behavior with an ION/IOFF value higher than 105, as well as an increase of threshold voltage as the NW width is reduced. Then, using a capacitive coupling in our dually-gated Si bioFETs, the pH sensitivity is enhanced with a pH response up to 600 mV/pH. Finally, we successfully detected an increase of threshold voltage of n-type silicon nanowires (SiNWs) due to hybridized target DNA molecules.

The large energy release potential and highly adjustable combustion characteristics of nanostructured silicon compounded with sodium perchlorate (NaClO4) make it one of the most attractive inorganic energetic materials. Compared with nanoporous silicon, the silicon nanowires prepared by metal-assisted chemical etching are easily loaded with NaClO4 to obtain energetic materials, due to their one-dimensional array structure and tight contact with the silicon substrate. However, the high hygroscopicity of NaClO4 greatly degrades the long-term storage property of the material, and must be addressed. In this study, sulfur, as a known stable and non-hygroscopic oxidant that reacts with nanostructured silicon, was impregnated on the silicon nanowires/NaClO4 energetic material to insulate NaClO4 from H2O in the ambient air. After sulfur impregnation, the mass of the sample increased by 8.7 ​mg after being exposed to 98% relative humidity at 25 ​°C for 12 ​h, while the sample without sulfur increased by 50 ​mg, indicating significant improvement in the hygrophobicity of the sulfur-containing energetic material. Laser ignition experiments showed that the combustion performance was only slightly affected after sulfur treatment. This work provides a new strategy for improving the hygrophobicity of silicon-based energetic materials, which can improve their applicability in micro-electromechanical systems.