Multilayered Nanowires Research Articles

Robust ZTO-reinforced Ag nanowire hybrid transparent conductive thin films with absorption-enhanced electromagnetic interference shielding property

Technological advances have accelerated the pursuit of transparent conducting thin films (TCFs) with superior mechanical properties, durability, efficient optoelectrical performance and substrate compatibility as a pivotal focus in the realm of flexible transparent electronics. Against this background, this work investigates the fabrication of multilayer silver nanowire (AgNW) thin films reinforced by zinc tin oxide (ZTO) thin film encapsulation on polycarbonate substrates by a combination of sputtering and spin-coating techniques. An investigation of the influence of AgNW percolation networks on the optoelectrical properties of ZTO/AgNW/ZTO hybrid thin films was carried out. The impact of ZTO protective layers on the enhancement of electrical properties, adhesivity, flexibility and environmental stability of the multilayer TCF was elucidated. Additionally, to explore the compatibility of the fabricated TCF in integrated device and stealth applications, its electromagnetic interference shielding properties were investigated. The hybrid TCF showed 99.47% EMI shielding efficiency with an absorption-dominant EMI shielding effectiveness of 22.7 dB in the x-band region.

Fabrication of Electronically Conductive Protein-Heme Nanowires for Power Harvesting.

Electronically conductive protein-based materials can enable the creation of bioelectronic components and devices from sustainable and nontoxic materials, while also being well-suited to interface with biological systems, such as living cells, for biosensor applications. However, as proteins are generally electrical insulators, the ability to render protein assemblies electroactive in a tailorable manner can usher in a plethora of useful materials. Here, an approach to fabricate electronically conductive protein nanowires is presented by aligning heme molecules in proximity along protein filaments, with these nanowires also possessing charge transfer abilities that enable energy harvesting from ambient humidity. The heme-incorporated protein nanowires demonstrate electron transfer over micrometer distances, with conductive atomic force microscopy showing individual nanowires having comparable conductance to other previously characterized heme-based bacterial nanowires. Exposure of multilayer nanowire films to humidity produces an electrical current, presumably through water molecules ionizing carboxyl groups in the filament and creating an unbalanced total charge distribution that is enhanced by the heme. Incorporation of heme and potentially other metal-center porphyrin molecules into protein nanostructures could pave the way for structurally- and electrically-defined protein-based bioelectronic devices.

Modulated critical currents of spin-transfer torque-induced resistance changes in NiCu/Cu multilayered nanowires.

We present a novel method combining anodic aluminum oxide template synthesis and nanolithography to selectively deposit vertically patterned magnetic nanowires on a Si substrate. With this approach we fabricated three-dimensional nanowire-based spin valve devices without the need of complex etching processes or additional spacer coating. Through this method, we successfully obtained NiCu/Cu multilayered nanowire arrays with a controlled sequence along the long axis of the nanowires. Both magnetic switching and excitation phenomena driven by spin-polarized currents were clearly demonstrated in our NiCu/Cu multilayered nanowires. Moreover, the critical currents for switching and excitation were observed to be modulated in an oscillatory manner by the magnetic field in the nanowire-based devices. We present a toy model to qualitatively explain these observations.

Angular first-order reversal curve analysis of FeNi/Cu multilayered nanowire arrays with different diameters

The main goal of the emerging field of spintronics is the shrinkage of materials and devices while improving their magnetic performance for a variety of applications, especially three-dimensional information storage. This stipulates the understanding of fundamental magnetic mechanisms such as magnetization reversal and switching events in multilayer systems with tunable size. Here, a porous anodic alumina membrane-assisted electrochemical deposition method is employed to fabricate FeNi/Cu multilayered nanowire arrays (MNWAs) with diameters in the range of D = 35–80 nm. Angular magnetic properties of these MNWAs are investigated via hysteresis loop and first-order reversal curve (FORC) measurements for angle fields of 0° ≤ θ ≤ 90°. While the former indicates the existence of different contributions of vortex domain wall propagation for smaller (D ≤50 nm) and larger (D >50 nm) diameters, the latter reveals the occurrence of single vortex states, depending on θ and D. Moreover, at θ = 0°, a transition from single domain to multidomain-like behavior appears to occur with increasing D from 35 to 80 nm based on FORC diagrams, significantly influencing magnetization reversibility of magnetic FeNi segments with relatively high aspect ratios (>5). The variation of magnetostatic interactions with respect to θ is discussed and compared at each diameter as an effective factor in determining angular magnetic properties. Also, the axial variation behavior of coercivity as a function of D is correlated with changes in the reversible percentage, shedding light on the expectations from the vortex domain wall propagation.

Tunable reflection coating to reduce exposure power threshold for interference-assisted two-photon polymerization lithography

We proposed a strategy to significantly reduce the exposure power threshold for two-photon lithography on tunable reflection coating substrates. The focused light spot at the photoresist-reflective interface is modulated into a multi-layered distribution, which has an enhanced optical field compared to the incident light. The interference of incident and reflected light at the interface enhances the local light field by 1.6–3.4 times, equivalent to reducing the incident exposure power. The tailored multilayer nanowires fabricated by a single scan and the exposure power modulation mechanism proposed in this study would be of profound importance in the fields of semiconductor electronic devices.

Multilayer Graphene-Coated Silicon Carbide Nanowire Formation Under Defocused Laser Irradiation

Graphene-coated silicon carbide (SiC@C) core–shell nanostructures have attracted attention in the fields of energy storage and nanoelectronics. In this study, multilayer graphene-coated silicon carbide (SiC) nanowires were obtained through the laser irradiation of a mixture target of graphite powder and silicon (Si) grinding sludge discharged from Si wafer manufacturing. Laser irradiation was performed using an ytterbium (Yb) fiber pulsed laser with a pulse width of 10 ms and a wavelength of 1070 nm with various defocus distances. The effect of laser defocusing on the morphology of the generated nanostructures was investigated. Results showed that nanowires were produced under the defocused conditions, and nanoparticles were observed at the on-focus position. The products obtained under all defocused conditions showed a core–shell structure, and the SiC nanowires were covered by graphene layers. The aspect ratio of the nanowires increased with the defocus distance. Observation of the laser-induced plume using a high-speed camera showed that when the laser was defocused, the plume propagation speed slowed down, and the shape of the plume changed to a swirling vortex. The nanowire formation was closely related to the propagation speed and shape variation of the plume. This successful production of SiC@C core–shell nanowires from Si waste opens up the possibility of the sustainable development of new materials for energy storage and nanoelectronics.

Interplay between diffusion and magnon-drag thermopower in pure iron and dilute iron alloy nanowire networks

Results of measurements on the thermoelectric power of 45 nm diameter interconnected nanowire networks consisting of pure Fe, dilute FeCu and FeCr alloys and Fe/Cu multilayers are presented. The thermopower values of Fe nanowires are very close to those found in bulk materials, at all temperatures studied between 70 and 320 K. For pure Fe, the diffusion thermopower at room temperature, estimated to be around − 15 upmuV/K from our data, is largely supplanted by the estimated positive magnon-drag contribution, close to 30 upmuV/K. In dilute FeCu and FeCr alloys, the magnon-drag thermopower is found to decrease with increasing impurity concentration to about 10 upmuV/K at 10% impurity content. While the diffusion thermopower is almost unchanged in FeCu nanowire networks compared to pure Fe, it is strongly reduced in FeCr nanowires due to pronounced changes in the density of states of the majority spin electrons. Measurements performed on Fe(7 nm)/Cu(10 nm) multilayer nanowires indicate a dominant contribution of charge carrier diffusion to the thermopower, as previously found in other magnetic multilayers, and a cancellation of the magnon-drag effect. The magneto-resistance and magneto-Seebeck effects measured on Fe/Cu multilayer nanowires allow the estimation of the spin-dependent Seebeck coefficient in Fe, which is about − 7.6 upmuV/K at ambient temperature.

Size dependence for mechanical properties of Ti/Cu multilayered nanowire with a semi-coherent interface

Metallic multilayered nanowires have a wide application prospect in micro-nano devices because of their superior physical and chemical properties and microstructure designability. Size effects on the tensile behaviors of Ti/Cu multilayered nanowires are investigated by molecular dynamic simulations. Aspect ratios of 1:4, 1:3, 1:2, 1:1, 1:0.75, and 1:0.67 and sectional dimensions of 3, 4, 5, 6, and 7 nm are adopted to construct nanowires with different sizes. Simulation results indicate that the strength of Ti/Cu nanowires decreases with the decrease of aspect ratio in the large aspect ratio range (>1:2) and all simulated sectional dimension ranges, showing a reverse Hall-Petch effect. The Hall-Petch law can only be satisfied in a small aspect ratio range (<1:2). Deformation mechanism transition is found in the critical aspect ratio of 1:2. When the aspect ratio is larger than 1:2, crystalline phases of Ti and Cu layers dominate the plastic deformation of Ti/Cu nanowires. Crystal phases and interface both bear plastic deformation when the aspect ratio is smaller than 1:2. Interface is an important factor in the strength and deformation of Ti/Cu nanowires. The variation of interface fraction and interaction between interface and dislocation motion determine the tendency of strength variation for Ti/Cu nanowires.

Fabrication of multilayer and silver oxide nanowires using electro-chemical deposition in the anodic aluminum oxide template

&lt;p&gt;In this paper, to fill molds, we have applied the electrochemical deposition method. The electrochemical deposition method to produce nanowires is performed by three different methods. We have examined the pulsed periodic method, and we have managed to fabricate the multilayer nanowires Ag/Co/Zn. Then, the produced nanowires are confirmed by the SEM and XRD analyses. Also, by putting the sample containing nanowires of Ag in the oven, the oxidation happened, and the nanowires of silver oxide are fabricated and confirmed by the XRD diffraction pattern.&lt;/p&gt;

Tuning magnetostatic interaction and coercivity distributions of FeCo/Cu multilayer nanowire arrays by variation of magnetic and nonmagnetic layer aspect ratios

FeCo/Cu multilayer NW arrays are fabricated using a pulsed electrodeposition method in 50 nm pore diameter anodic aluminum oxide templates. The magnetic layer (LFeCo) and nonmagnetic layer (LCu) thicknesses range between 23–225 and 2–50 nm, respectively. These layer designations make it possible to find a thin Cu layer, in which the magnetic behavior of multilayer NWs is similar to that of alloy NWs. A threshold LCu is also obtained, representing dual behavior of the coercive field in FeCo/Cu multilayer NWs. These behaviors, in turn, are associated with an increase in magnetizing and demagnetizing interactions, as evidenced by hysteresis curve and first-order reversal curve experiments. By extracting magnetic parameters such as the average coercive field, irreversible coercive field, magnetostatic interaction distribution, and reversibility, the magnetic behavior of FeCo/Cu multilayer NWs is comprehensively explored as a function of LFeCo.

Synthesis of NiO/Nitrogen-Doped Carbon Nanowire Composite with Multi-Layered Network Structure and Its Enhanced Electrochemical Performance for Supercapacitor Application.

Multi-layered NiO nanowires linked with a nitrogen-doped carbon backbone grown directly on flexible carbon cloth (NiO/NCBN/CC) was successfully fabricated with a facile synthetic strategy. The NiO/NCBN/CC was further used as a binding-free electrode for flexible energy storage devices, showing a boosted performance including a high capacitance of 1039.4 F g−1 at 1 A g−1 and an 83.4% capacitance retention ratio. More importantly, after 1500 cycles, the capacitance retention can achieve 72.5% at a current density of 20 A g−1. The excellent electrochemical properties of the as-prepared NiO/NCBN/CC are not only attributed to the multi-layered structure that can help to tender unimpeded channels and accommodate the electrolyte ions around the electrode interface during the charge–discharge process, but is also due to the link between the NiO and N-doped carbon backbone and the nitrogen doping on the carbon substrate, which results in extra defects on the surface that could boost the interfacial electron transfer rate of the electrode.

Fabrication of Multilayer Nanowires (Ag/Co/Zn) by Electro-Chemical Deposition in the Anodic Aluminum Oxide Template

Fabrication of Multilayer Nanowires (Ag/Co/Zn) by Electro-Chemical Deposition in the Anodic Aluminum Oxide Template

Study of Structural, Morphological and Electrochemical Properties of Multilayer Nanowires

Ni/Cu nanowires were fabricated by electrodeposition in potentiostatic mode, into the pores of polycarbonate membrane. In present work metallic multilayer nanowires were deposited in polycarbonate membrane having pore size of 400 nm. It is found that the growth of nanowires is not constant, it varies with the pH values of electrolyte used for the deposition. Scanning electron microscopy (SEM) confirmed formed nanowires are cylindrical in shapes, dense and homogeneous for low pH depostion. X-ray diffraction technique is used to study the morphology and structure of fabricated Ni/Cu nanowires and found nanowires have FCC structure. An energy dispersive X-ray spectroscopy (EDS) is used to study the composition of multilayer nanowires. The electrochemical impedance spectroscopy has been carried out to study the in-situ growth process of multilayer nanowires.&#x0D; HIGHLIGHTS&#x0D; &#x0D; Fabricated Ni/Cu nanowires using electrodeposition method in potentiostatic mode, into the pores of polycarbonate membrane&#x0D; Scanning electron microscopy (SEM) confirmed that the fabricated nanowires are cylindrical in shape, dense and homogeneous for low pH value&#x0D; XRD study reveals FCC structure of fabricated nanowires&#x0D; &#x0D; GRAPHICAL ABSTRACT

A novel strategy to improve giant magnetoresistance effect of Co/Cu multilayered nanowires arrays

Giant magnetoresistance (GMR) effect exhibits high potential applications in ultrahigh density magnetic recording, magnetic sensors and electronic devices. Many methods were developed to improve the GMR, such as changing the diameters or content ratio of Co to Cu etc. In this work, we have successfully grown a new Co/Cu multilayered magnetic nanowires arrays (MNAs) with gradient diameter (GDMNAs). Very interestingly, we demonstrate much enhanced GMR in the GDMNAs. Moreover, it shows higher thermal stability simultaneously. This is a novel strategy to improve GMR. Generally, the diameter (d) and edge-to-edge separation (s) of MNAs play a significant role in determining the magnetic properties. If d<s, exchange interaction dominants. If d>s, dipolar interaction dominates. When we design a new GDMNAs with d<s at one end and d>s at the other, much better multilayered structures are observed on the larger end. Surprisingly, the magnetic anisotropy is found to be dominated by the portion of MNAs with d<s. Combining both properties in GDMNAs, we achieve the highest GMR value of 27% in reported Co/Cu MNAs. This design strategy not only reveals new interesting physics, which remains to be understood, but also useful to other applications based on MNAs.

Magnetization reversal properties and magnetostatic interactions of disk to rod-shaped FeNi layers separated by ultra-thin Cu layers

From fast magnetic memories with low-power consumption to recording media with high densities, realizing the magnetization reversal and interaction of magnetic layers would allow for manipulating the ultimate properties. Here, we use a pulsed electrochemical deposition technique in porous alumina templates (50 nm in pore diameter) to fabricate arrays of nanowires, consisting of FeNi layers (26−227 nm in thickness) with disk to rod-shaped morphologies separated by ultra-thin (3 nm) Cu layers. By acquiring hysteresis curves and first-order reversal curves (FORCs) of the multilayer nanowire arrays, we comprehensively investigate magnetization reversal properties and magnetostatic interactions of the layers at different field angles (0° ≤ θ ≤ 90°). These involve the extraction of several parameters, including hysteresis curve coercivity (H c Hyst ), FORC coercivity (H c FORC ), interaction field distribution width (ΔH u ), and irreversible fraction of magnetization (IF m ) as a function of θ. We find relatively constant and continuously decreasing trends of H c Hyst when 0° ≤ θ ≤ 45°, and 45° < θ ≤ 90°, respectively. Meanwhile, angular dependence of H c FORC and IF m shows continuously increasing and decreasing trends, irrespective of the FeNi layer morphology. Our FORC results indicate the magnetization reversal properties of the FeNi/Cu nanowires are accompanied with vortex domain wall and single vortex modes, especially at high field angles. The rod-shaped layers also induce maximum ΔH u during the reversal process, owing to enhancements in both magnetizing and demagnetizing-type magnetostatic interactions.

The role of the addition of Cu in alloyed and multilayered Fe-based nanowires

In this research, we focused on studies of the influence of Cu addition on the structure and magnetic properties of FeCu-alloyed and Fe/Cu-multilayered nanowires electrodeposited into polycarbonate membranes. It was observed that Cu addition prevents oxidation of overdeposited caps, compared to the surface of membranes filled with pure Fe, which immediately becomes covered with an oxide layer in the air. TEM studies revealed the polycrystalline structure of the multilayered NWs and confirmed that the wires were composed of alternating Fe and Cu layers. Magnetic studies performed using a SQUID magnetometer indicated a magnetic anisotropy with an easy axis along the nanowires. The increase in the Cu concentration in alloyed nanowires from 10% to 30%, resulted in an increase in both coercivity and squareness by about 30%. In the case of multilayered nanowires, significant reduction in squareness and non-monotonic changes in coercivity with the increase in Cu layer thickness were observed.

Toughening in low-dimensional nanomaterials high-entropy ceramic nanocomposite

Very recently, high entropy concept has evolved from metal to the ceramic community, named as high entropy ceramics (HEC). The configurational entropy endowed the system with unique structure, performances as well as application potentials such as aerospace, high-speed machining tools, and nuclear reactors. However, the poor densification together with low fracture toughness of HEC significantly limited the practical applications of HEC. Herein, we report for the first time the employment of low-dimensional nanomaterials including multilayer graphene (MLG), carbon nanotube (CNT) and SiC nanowire (SiC nw ) to improve the densification coupled with fracture toughness of HEC through two-step spark plasms sintering. HEC-MLG and HEC-SiC nw exhibited flexural strength of 671.3 MPa and 626.5 MPa, with fracture toughness of 7.1 MPa m 1/2 and 6.2 MPa m 1/2 , respectively. The strength and toughness of HEC nanocomposites were both greater than those of the reported values for high entropy ceramics. The reinforcing mechanisms were discussed in detail for all the three HEC nanocomposites. Overall, this paper demonstrated that the toughening methods for normal ceramics were also feasible for HEC matrix, significantly increasing the freedom to tailor the properties and applications of HEC. • Low-dimensional nanomaterials were proposed for reinforcing high entropy ceramic. • Two-step spark plasms sintering was employed to densify high entropy ceramic. • The compromise between strength and toughness occurred to high entropy ceramic. Graphene and SiC nw performed better roles than CNT in toughening high entropy ceramic.

Morphologies evolution and mechanical behaviors of SiC nanowires reinforced C/(PyC-SiC) multilayered matrix composites

• The bionic (PyC-SiC) n multilayered structure was used to improve flexural properties. • The SiC nanowires formed in-situ on the surface of multilayered structure played an important role in micro-zone reinforcements. • The (PyC-SiC) n multilayered structure and SiC nanowires were prepared at the same time, and they could form a multiscale reinforcing system. • The flexural strengths and flexural modulus of modified composites were up to 62.36% and 102.20% respectively higher than C/C composites. SiC nanowires reinforced C/(PyC-SiC) n multilayered matrix composites (SM-CS for short) were prepared by combined with sol-gel and chemical vapor infiltration (CVI) method. Firstly, (PyC-SiOC) n multilayered structure was formed by cycles of impregnation and deposition. Then SiOC was transformed into SiC by heat-treatment, and (PyC-SiC) n multilayered structure would be obtained. At the same time, the PyC layer which was designed as the outmost layer could decrease gas supersaturation to form in-situ tubular SiC nanowires on the surface of multilayered structure. The results of three-point bending test showed that the maximum force of SM-CS composites was increased by the number of cycles of the preparation process, which were up to enhanced by 74.38% compared with C/C composite materials. The fracture surface showed that the improvement was due to the multiscale reinforcing system of (PyC-SiC) n multilayered structure and SiC nanowires. Multilayered structure can protect carbon fibers and release stress concentration by induction of cracks. And the mechanical interlocking effect of SiC nanowires could reinforce bonding force of the remaining matrix.

A Novel Strategy to Improve Giant Magnetoresistance Effect of Co/Cu Multilayered Nanowires Arrays

A Novel Strategy to Improve Giant Magnetoresistance Effect of Co/Cu Multilayered Nanowires Arrays

1D Nanomaterials in Fe‐Group Metals Obtained by Synthesis in the Pores of Polymer Templates: Correlation of Structure, Magnetic, and Transport Properties

1D cylindrical magnetic nanostructures (FeNi, FeCo, FeCoP) of complex topology such as nanowires (NWs), nanotubes (NTs), multilayered nanowires, and core–shell structures are discussed from the perspective of engineering a wide variety of magnetic materials from hard to semihard to soft. Most of recent data are given for the materials synthesized in the pores of polymer ion‐track membranes, which makes it possible to tune systematically the geometrical parameters, morphology, and composition. The key properties including crystal and micromagnetic structure, magnetic anisotropy, and coercivity are analyzed. Co‐based NWs with uniform morphology demonstrate coercivity of more than 10 kOe due to the combination of crystalline and shape anisotropies. In the case of NTs, the demagnetizing effect is reduced owing to a helical arrangement of the magnetization, which leads to low values of coercivity and remanence magnetization. Varying the geometrical parameters of multilayered NWs, the alternating soft and semihard magnetic layers can be made within a single nanowire, which is important for spin‐valve magnetoresistance. Au‐coated ferromagnetic nanostructures are biocompatible and can be used to enhance optical absorption. Ni@Au NTs used as substrates for Raman spectroscopy demonstrate the enhancement factor of the order of 104. Some aspects related to applications of 1D magnets are briefly overviewed.