Multiple Nanowire Research Articles

Development of a Biolabeling System Using Ferromagnetic Nanowires

This paper presents the development of a biolabeling system using different ferromagnetic nanowire types. The proposed biolabeling system concept includes a cell separation procedure description using magnetic nanowires and how nanowires can be used and identified as biolabels. A study on single magnetic nanowire behavior is performed, and the algorithm used to characterize and identify each nanowire type separately and from a mix of multiple types is described. The algorithm is verified using measurement data from individual nanowire array samples and stacked combinations of cobalt, iron, and nickel. From the strong correlation between the measured transmission coefficient data of magnetic nanowire arrays and a mathematical model, the potential of interpreting multiple magnetic nanowire types inside cells is confirmed.

Carbon Nanotube-Inorganic Hybrid Systems and Devices

We present different strategies for the generation of multifunctional nanomaterials employing single-walled carbon nanotubes (SWCNTs). In particular, we will discuss the formation of nanohybrids via the in-solution assembly of inorganic nanomaterials to SWCNTs, employed as nanoelectrodes or as nanoscale vector templates. Notably, both static and dynamic heterostructures were assembled, as well as nanoscale electronic devices; this allowed us to study and tailor various systems for different applications. We will first discuss the in-solution assembly of organic-inorganic heterostructures consisting of single Quantum Dots (QDs) univocally linked at the terminal ends of individual SWCNTs. Monofunctionalized SWCNT-QD heterostructures were obtained and photophysical investigations at the single nanohybrid level showed evidence of electronic coupling [1]. Additionally, DNA linkers of differing lengths were used as molecular rulers to control the distance, and hence tune the energy/charge transfer between the two nanostructures in these SWCNT-QD nanohybrids.[2] A dynamic SWCNT-QD hybrid was also designed and assembled using a G-quadruplex DNA aptamer linker, so that the distance between the SWCNT and QD could be dynamically modulated by the introduction and removal of potassium ions (K+);[2] the system was further found to be sensitive to K+ concentrations between 1pM and 25mM. By and large, this approach opens the possibility of assembling tailored optoelectronic and light harvesting systems with single-particle control. Finally, we will present the direct synthesis of multiplexed metal nanowire based devices using carbon nanotubes as vector templates. SWCNTs were filled with specifically designed metal precursors and dispersed in aqueous solution, enabling solution processability. The filled SWNTs were immobilized from solution onto different pre-patterned electrodes via a low-cost dielectrophoresis methodology. Metal nanowires were then grown by a facile and low temperature annealing treatment, while the nanotubes were removed using an oxygen plasma once immobilized in a device configuration. Electrical characterizations demonstrated the successful fabrication of metal nanowire electronic devices (no gate dependence).[3] Overall the strategy presented allows for a facile, low-cost and direct synthesis of multiple metal nanowire based devices for nanoelectronic applications. [1] Small, 2017,13, 1603042 [2] Advanced Science, 2018, 5, 1800596 [3] Submitted

The ultra-sensitive visual biosensor based on thermostatic triple step functional nucleic acid cascade amplification for detecting Zn2+

Here, we present an ultra-sensitive visual biosensor based on thermostatic triple step functional nucleic acid cascade amplification for detecting Zn2+. A Zn2+-assisted cDNAzyme assay is conducted and the Zn2+ is successfully converted into nucleic acids to achieve the first circular amplification within 1 h. The cleavage products prompted Hybridization Chain Reaction (HCR), forming multiple DNA nanowire structures with branched chains. And the Strand Displacement Amplification (SDA) were further empowered by the HCR products with the addition of the amplification enzyme and the endonuclease. In just 80 min, the second and third-order signal amplifications are reached. With the addition of Hemin and chromogenic substrates, the visual signal output is achieved in 15 min based on the large amount of G-quadruplex (G4) DNAzymes. This biosensor can detect levels as low as 1.075 pM Zn2+, showing a good linear range within 10 pM–100 nM. It shows considerable potential for the Zn2+ quantitative detection.

Collective quantum phase slips in multiple nanowire junctions

Realization of robust coherent quantum phase slips represents a significant experimental challenge. Here we propose a new design consisting of multiple nanowire junctions to realize a phase-slip flux qubit. It admits good tunability provided by gate voltages applied on superconducting islands separating nanowire junctions. In addition, the gates and junctions can be identical or distinct to each other leading to symmetric and asymmetric setups. We find that the asymmetry can improve the performance of the proposed device, compared with the symmetric case. In particular, it can enhance the effective rate of collective quantum phase slips. Furthermore, we demonstrate how to couple two such devices via a mutual inductance. This is potentially useful for quantum gate operations. Our investigation on how symmetry in multiple nanowire junctions affects the device performance should be useful for the application of phase-slip flux qubits in quantum information processing and quantum metrology.

ZnO Nanowire Application in Chemoresistive Sensing: A Review.

This article provides an overview of the recent development of ZnO nanowires (NWs) for chemoresistive sensing. Working mechanisms of chemoresistive sensors are unified for gas, ultraviolet (UV) and bio sensor types: single nanowire and nanowire junction sensors are described, giving the overview for a simple sensor manufacture by multiple nanowire junctions. ZnO NW surface functionalization is discussed, and how this effects the sensing is explained. Further, novel approaches for sensing, using ZnO NW functionalization with other materials such as metal nanoparticles or heterojunctions, are explained, and limiting factors and possible improvements are discussed. The review concludes with the insights and recommendations for the future improvement of the ZnO NW chemoresistive sensing.

Multispectral absorptance from large-diameter InAsSb nanowire arrays in a single epitaxial growth on silicon

Vertical III-V nanowires are capable of resonant absorption at specific wavelengths by tuning the nanowire diameter, thereby exceeding the absorption of equivalent thin films. These properties may be exploited to fabricate multispectral infrared (IR) photodetectors, directly integrated with Si, without the need for spectral filters or vertical stacking of heterostructures as required in thin film devices. In this study, multiple InAsSb nanowire arrays were grown simultaneously on Si by molecular beam epitaxy with nanowire diameter controlled by the nanowire period (spacing between nanowires). This is the first such study of patterned InAsSb nanowires where control of nanowire diameter and multispectral absorption are demonstrated. The antimony flux was used to control axial and radial growth rates using a selective-area catalyst-free growth method, achieving large diameters, spanning 440–520 nm, which are necessary for optimum IR absorption. Fourier transform IR spectroscopy revealed IR absorptance peaks due to the HE11 resonance of the nanowire arrays in agreement with optical simulations. Due to the dependence of the HE11 resonance absorption on nanowire diameter, multispectral absorption was demonstrated in a single material system and a single epitaxial growth step without the need for bandgap tuning. This work demonstrates the potential of InAsSb nanowires for multispectral photodetectors and sensor arrays in the short-wavelength IR region.

Sonochemical assisted synthesis of RGO/ZnO nanowire arrays for photoelectrochemical water splitting

This article presented the synthesis of a hybrid nanoarchitecture material composed of reduced graphene oxide (RGO) multiple sheets and ZnO nanowire arrays (NWAs) formed on an arbitrary ZnO coated fluorine doped tin oxide (FTO) substrates via pulse sonication and hydrothermal approach. The NWAs have high aspect-ratio, high density, apt positioning and well-ordered formation. FESEM images demonstrated that RGO layers have been effectively intercalated between and on the accessible surfaces of the ZnO NWAs. The diameter of ZnO nanowires is 80–150nm and length about 1–2μm. Raman spectrum of hybrid material exhibited characteristic D and suppressed G peaks for graphene and E2 mode at 437cm−1 for ZnO NWAs. UV–visible spectrum indicated slight red shift towards visible range after formation of RGO/ZnO NWAs heterostructure. The Photoelectrochemical results indicated higher current densities for RGO/ZnO NWAs heterostructure due to water oxidation reaction at the working electrode compared to pristine ZnO NWAs.

Conduction mechanisms in SnO2 single-nanowire gas sensors: An impedance spectroscopy study

Results of studies on single and multiple SnO2 nanowire gas sensors with impedance spectroscopy are reported. Equivalent circuit modeling is used to draw fundamental conclusions about the dominant conduction mechanism in single-nanowire sensors, where the diameter of the nanowire is found to play a key role. This is then extended to multiple-nanowire sensors. For single-nanowire sensors, I–V measurements are also used to demonstrate that the contribution from the electrode-nanowire contact to the overall resistance changes with atmosphere and temperature. We find that for the randomly-orientated multiple-nanowire sensors, the main contribution to the resistance comes from the nanowire–nanowire junction.

Power Response of a Planar Thermoelectric Microgenerator Based on Silicon Nanowires at Different Convection Regimes

Abstract A thermoelectric microgenerator based on multiple silicon nanowire arrays is fabricated and its performance evaluated for different convection regimes. Mature silicon microfabrication technology is used to fabricate the device structure. As a post-process, a bottom-up approach is used to grow silicon nanowires by a VLS-CVD mechanism. The thermal design of the microgenerator features a thermally isolated silicon platform which is connected to the bulk silicon rim through several arrays of silicon nanowires. Simulations are carried out to evaluate the need of an external heat sink to improve the thermal gradient seen by the nanowires and the power output of the microgenerator. Results show a significant improvement with a heat sink raising the thermal gradient from 3 K to approximately 100 K when the external temperature gradient is 300 K. Experimental measurements with different convection regimes also show a radical improvement on the power output comparing natural convection and two different forced convection regimes. The first forced convection regime is a broad airflow from a commercial CPU fan placed on top of the device, while the second (air jet forced convection) uses a syringe to focus the airflow from the compressed air line to the platform. The maximum output power for a natural convection regime is 2.2 nW for a hotplate temperature of 200 °C, while the air jet forced convection regime generates up to 700 nW, which correspond to 35 µW/cm2 considering a device footprint of 2 mm2.

Near-Unity Unselective Absorption in Sparse InP Nanowire Arrays

We experimentally demonstrate near-unity, unselective absorption, broadband, angle-insensitive, and polarization-independent absorption, in sparse InP nanowire arrays, embedded in flexible polymer sheets via geometric control of waveguide modes in two wire motifs: (i) arrays of tapered wires and (ii) arrays of nanowires with varying radii. Sparse arrays of these structures exhibit enhanced absorption due to strong coupling into the first order azimuthal waveguide modes of individual nanowires; wire radius thus controls the spectral region of the absorption enhancement. Whereas arrays of cylindrical wires with uniform radius exhibit narrowband absorption, arrays of tapered wires and arrays with multiple wire radii expand this spectral region and achieve broadband absorption enhancement. Herein, we present an economic, top-down lithographic/etch fabrication method that enables fabrication of multiple InP nanowire arrays from a single InP wafer with deliberate control of nanowire radius and taper. Using this...

Vertically Integrated ZRAM toward Extremely Scaled Memory

This paper discusses the demonstration of a vertically integrated gate-all-around (GAA) silicon nanowire (SiNW) channel-based dynamic random access memory (DRAM) without a cell-capacitor as a breakthrough for conventional DRAM scaling. Owing to the one-route all-dry etching process (ORADEP) with stiction-free stability and process simplicity, vertical integration of multiple silicon nanowire was achieved with high uniformity and high reproducibility. Finally, high performance suitable for further scaling was presented in zero-capacitor DRAM (ZRAM) operable with up to five-story SiNW channels without sacrificing scalability.

Organic Single-Crystal Nanowire Transistor Fabricated by Glass Fiber Mask Method

The commercialized, low-cost, and lightweight glass fiber microwires have been shown as a new mask to simplify the fabrication of organic single-crystal nanowire transistors based on copper phthalocyanine (CuPc). The glass fiber is light weight so that the van der Waals force is capable of resisting the effect of gravity when the substrate is flipped over. In this case, the glass fiber mask need not be artificially fixed onto the substrate during metal deposition for electrode fabrication, so the device fabrication process can be simplified. With such a facile method, multiple organic single-crystal nanowire transistors can be fabricated at the same time, and the high mobility up to 0.7 cm $^{2}\text{V}^{{-1}}\text{s}^{{-1}}$ has been realized for CuPc nanowire transistors. Good stability has been also demonstrated. This method effectively improves the efficiency of devices preparation, showing the potential in large-scale fabrication of organic nanowire transistors. Meanwhile, it is favorable for the fundamental electrical studies of 1-D organic nanomaterials.

Vertically Integrated Multiple Nanowire Field Effect Transistor.

A vertically integrated multiple channel-based field-effect transistor (FET) with the highest number of nanowires reported ever is demonstrated on a bulk silicon substrate without use of wet etching. The driving current is increased by 5-fold due to the inherent vertically stacked five-level nanowires, thus showing good feasibility of three-dimensional integration-based high performance transistor. The developed fabrication process, which is simple and reproducible, is used to create multiple stiction-free and uniformly sized nanowires with the aid of the one-route all-dry etching process (ORADEP). Furthermore, the proposed FET is revamped to create nonvolatile memory with the adoption of a charge trapping layer for enhanced practicality. Thus, this research suggests an ultimate design for the end-of-the-roadmap devices to overcome the limits of scaling.

Field-directed chaining of nanowires: towards transparent electrodes

Nanowire networks on rigid or flexible substrates can be used as low-cost transparent electrodes for displays, photovoltaics and as sensors. Generating an ordered configuration of connected nanowires from disordered suspension requires external forces. We demonstrate chaining of nanowires, using an AC electric field to generate dielectrophoretic force on nanowires adjacent to the electrodes and dipole–dipole interaction between nanowires far from the electrodes. Classifying and controlling forces and parameters that disrupt chaining, we provide guidelines to enable large-area coverage with multiple nanowire chains. Compared with other low-cost techniques such as spray or spin coating, AC electric field-directed assembly provides control over density and connectivity of nanowire chains with potential for fabricating low-cost, high-performance devices.

Direct growth, characterization, and optical properties of silica nanowires on cordierite monolith

We report the direct synthesis of amorphous silica nanowires on cordierite monolith. Our approach is based on a simple catalyst-assisted growth using Sn particles that are formed via the mechanochemical reaction of SnO2 (s) with Al (s, l) or Si (s) during the initial phase of the growth process. The silica nanowires have a diameter of approximately 20nm and become densely packed upon repeatedly branching and merging with each other. The silica nanowire assemblies grow up to 50µm in length. The microscopic images reveal that the Sn catalysts govern the growth by controlling the formation of the nuclei on their surface. Remarkably, the Sn catalysts induce the growth of multiple silica nanowire assemblies and the formation of Sn-rich amorphous (Si,Al)Ox nanotube/Al-doped orthorhombic Mg2SiO4 nanofiber as a minor product. The Sn-catalyzed silica nanowires show strong blue emission.

Room temperature hydrogen sensing performances of multiple networked GaN nanowire sensors codecorated with Au and Pt nanoparticles

The sensing performances of multiple networked GaN nanowire (NW) sensor codecorated with Au and Pt nanoparticles were examined. The pristine GaN nanowires show responses of approximately 108%–173% to 0.05%–0.25% H2 at room temperature. On the other hand, the GaN nanowires decorated with Au and those decorated with Pt lead to 1.1–1.3 and 1.2–1.6 times, respectively, stronger responses to 0.05%–0.25% H2. In contrast, the AuPt-codecorated GaN nanowires show 1.3–2.0 times stronger responses to 0.05%–0.25% H2. In other words, the GaN nanorods codecorated with Au and Pt nanoparticles show much stronger response to H2 gas than the Au or Pt monometal-decorated counterpart. The underlying mechanism for the enhanced response of the AuPt-codecorated GaN nanowire was discussed.

Fabrication, structure and hydrogen-gas-sensing properties of multiple networked GaN nanostructure gas sensors

The controlled synthesis of nanostructures with different shapes and morphologies has attracted considerable interest because the sensing properties of nanostructures depend on their structure, shape, phase, size, and size distribution, as well as their composition. This paper compares the responses of GaN nanostructures with different morphologies to hydrogen. The underlying mechanism for the hydrogen gas sensing of the multiple networked GaN nanowire sensor can be explained based on the well-established surface depletion model. On the other hand, the difference between two different samples, the GaN nanostructure sample synthesized at 1,100 °C and that synthesized at 1,000 °C, could be explained as follows: The major process behind the interaction between the nanostructures and hydrogen is the chemisorption of the dissociated hydrogen on the GaN surface. The chemisorption creates an electron accumulation layer on the GaN surface that enhances its electrical conductance. The GaN nanostructure sample synthesized at 1,100 °C with a higher ammonia flow rate showed a higher response to H2 gas than that synthesized at 1,000 °C with a lower ammonia flow rate, which might be attributed to the higher surface-to-volume ratio of the former.

Silicon nanowire networks for multi-stage thermoelectric modules

We present the fabrication and characterization of single, double, and quadruple stacked flexible silicon nanowire network based thermoelectric modules. From double to quadruple stacked modules, power production increased 27%, demonstrating that stacking multiple nanowire thermoelectric devices in series is a scalable method to generate power by supplying larger temperature gradient. We present a vertically scalable multi-stage thermoelectric module design using semiconducting nanowires, eliminating the need for both n-type and p-type semiconductors for modules.

Low-frequency noise in 2-bit poly-Si TANOS flash memory

In this work, the low-frequency noise (LFN) characteristics of single-gate (SG) and dual-gate (DG) TaN–Al2O3–Si3N4–SiO2–Si (TANOS) nonvolatile memories (NVMs) with multiple nanowire (multi-NW) channel structures and of DG TANOS NVM with a planar structure were investigated. In polycrystalline silicon TANOS NVM, a small wire channel width yielded a low grain boundary trap density (QT), and therefore a low LFN. After Fowler–Nordheim (FN) programming and erasing, the LFN level increments of both SG and DG TANOS NVMs with multi-NW channel structures were observed to be similar but larger than that of the NVM with a planar structure owing to the different areas that were occupied by corner regions. Additionally, the LFN characteristics of the DG TANOS NVM with multi-NW channel structures under FN and 2-bit modulated FN (MFN) operation were investigated and compared.

Light assisted room temperature ethanol gas sensing of ZnO-ZnS nanowires.

ZnO-core/ZnS-shell nanowires were synthesized by the thermal evaporation of a mixture of ZnO and graphite powders followed by the thermal evaporation of ZnS powders. Multiple networked nanowire gas sensors were then fabricated using the core-shell nanowires. The morphology, crystal structure and sensing properties of the ZnO-core/ZnS-shell nanowires to C2H5OH gas at room temperature under ultraviolet (UV) illumination were examined. The responses of the ZnO-core/ZnS-shell nanowires to C2H5OH gas were 1.2-2.1 times higher than those of the ZnO nanowires at C2H5OH concentrations ranging from 50 to 250 ppm under UV illumination. On the other hand, the resistance of the ZnO nanowires in the dark at room temperature was too high to measure. The underlying mechanism for the enhanced gas sensing properties of the ZnO-core/ZnS-shell nanowires toward C2H5OH gas is discussed.