Formation Mechanism Of Nanowires Research Articles

Fabrication of silver/silver-tetracyanoquinodimethane heterogeneous nanowires using nanoskiving method

In this study, silver/silver-tetracyanoquinodimethane nanowires with excellent microstructure quality are prepared by combining the nanoskiving method with the solution reaction method, and their electrical properties are tested. The perpendicular cutting direction and larger cutting thickness are beneficial to the acquisition of complete and less deformed silver nanowires. Silver/silver-tetracyanoquinodimethane heterogeneous nanowires can be precisely prepared at small droplet concentration, small droplet volume, and 60 s reaction time. The continuity, dimensions, and formation mechanism of nanowires are characterized by atomic force microscope and scanning electron microscope. Raman spectroscopy and transmission electron microscope revealed the successful formation and core-shell structure of silver-tetracyanoquinodimethane nanowires. The electrical properties of silver/silver-tetracyanoquinodimethane heterostructure nanowires show a typical Schottky barrier using a two-point electrical measurement method. This work lays a solid foundation for promoting the engineering application of silver nanowires and silver/silver-tetracyanoquinodimethane heterogeneous nanowires.

GaN nanowire arrays by a patterned metal-assisted chemical etching

We developed an one-step and two-step metal-assisted chemical etching method to produce self-organized GaN nanowire arrays. In one-step approach, GaN nanowire arrays are synthesized uniformly on GaN thin film surface. However, in a two-step etching processes, GaN nanowires are formed only in metal uncovered regions, and GaN regions with metal-covering show nano-porous sidewalls. We propose that nanowires and porous nanostructures are tuned by sufficient and limited etch rate, respectively. PL spectra shows a red-shift of band edge emission in GaN nanostructures. The formation mechanism of nanowires was illustrated by two separated electrochemical reactions occur simultaneously. The function of metals and UV light was illustrated by the scheme of potential relationship between energy bands in Si, GaN and standard hydrogen electrode potential of solution and metals.

Fabrication and Characterization of Lu$lt;inf$gt;2$lt;/inf$gt;O$lt;inf$gt;3$lt;/inf$gt; Nanowire Arrays by Sol-Gel Template Method Assisted with Ultrasonic Treatment

Lu2O3 nanowire arrays were fabricated by a Sol-Gel anodic aluminum oxide (AAO) template method assisted with ultrasonic treatment. The structure and morphology of Lu2O3 nanowire arrays were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), Energy disperse X-ray spectroscope (EDX), and transmission electron microscope (TEM). The results indicate that the as-prepared nanowire arrays consist of cubic structure of polycrystalline Lu2O3. The Lu2O3 nanowires are parallel to each other and quite uniform in diameter of about 200 nm. The formation mechanism of nanowires is also explored here. It is found that it is easy to evolve Lu2O3 into bamboo-like nanotubes without ultrasonic treatment. Compared with traditional Sol-Gel template method, a good filling of Lu2O3 nanowires embedded in the AAO template can be obtained by improved ultrasonicassisted technique. Ultrasonic treatment is useful to prepare for other nanowire arrays of different materials.

In-Plane Si Nanowire Growth Mechanism in Absence of External Si Flux.

We report on a new mechanism of nanowire formation: during Au deposition on Si(110) substrates, Au-Si droplets grow, move spontaneously, and fabricate a Si nanowire behind them in the absence of Si external flux. Nanowires are formed by Si dissolved from the substrate at the advancing front of the droplets and transported backward to the crystallization front. The droplet shape is determined by the Si etching anisotropy. The nanowire formation can be tuned by changing experimental parameters like substrate temperature and Au deposition rate.

Characterization and gas-sensing properties of NiO nanowires prepared through hydrothermal method

NiO nanowires with high aspect ratio and dispersive distribution have been synthesized by a hydrothermal reaction of NiCl2 with Na2C2O4 and H2O in the simultaneous presence of ethylene glycol (EG) and polyethylene glycol (PEG). Then the products were obtained by the subsequent annealing at 400°C in air. The effect of –OH from EG and –O– from PEG in the formation of nanowires was discussed. And the gas sensing properties of the as-prepared NiO nanowires toward ethanol were investigated. A novel formation mechanism of nanowires was presented and the NiO nanowires were proved to have an excellent gas sensing performance.

Mechanism of nanowire formation in metal assisted chemical etching

A simple, effective, and universal model is presented for the formation of silicon nanowires during silver metal assisted chemical etching of silicon. The model explains nanowire formation in terms of well-known and well-understood principles of electrochemical exchange current densities at silver metal/solution interfaces, silicon/silver ion reaction kinetics, and diffusion limited aggregatoon (DLA) kinetics. The role of the metal in the formation of nanowires is clearly defined and the model is easily extended to other transition metal systems, including: Pt, Au and Pd.

Formation of Nickel Nanowires by Electroless Deposition

The formation of nickel nanowires by electroless deposition was electrochemically investigated by an in-situ quartz crystal microbalance measurement combined with an in-situ mixed potential measurement. These electrochemical measurements revealed that the control of a terminal point of the nickel deposition reaction is critical for the formation of nanowires. The terminal point has been controlled by adjusting a concentration of sodium hydroxide and trisodium citrate. Based on the formation mechanism of nanowires, nickel nanowires 100-370 nm in diameter with several dozen μm of length were successfully prepared by controlling the terminal point and the nucleation rate.

Sb-Te Phase-change Nanowires by Templated Electrodeposition

ABSTRACTPhase-change memory materials (PCMMs) are semiconductors that exhibit rapid order-disorder transition under electrical or optical pulse excitation. Currently thin-film-based PCMMs play a dominant role in fabrication of non-volatile memory devices. In contrast, phase-change nanowires (PCNWs) have the potential to overcome future challenges such as high data density and low power consumption. Among the various methods to synthesize PCNWs, the vapor-liquid-solid method has been reported previously. In this paper, we report synthesis of Sb-Te PCNWs using a templated electrochemical method. Nanoporous anodic aluminum oxide (AAO) was used as a template for the growth of nanowires. Sb-Te PCNWs with different compositions, diameters and aspect ratios were grown inside the AAO template by electrodeposition. Composition and structure of these nanowires were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction, and scanning and transmission electron microscopy. It is found that electrodeposition through nanosized channels results in materials that are quite different from those electrodeposited on unrestricted surface. The mechanism of nanowire formation inside the channels of AAO template is discussed.

Low-temperature growth of tetragonal tungsten nanowire arrays on tungsten substrate using Ni solid catalysts

Tetragonal tungsten nanowire arrays were successfully fabricated on tungsten substrate using Ni catalysts by chemical vapor deposition (CVD) at 950 °C. The synthesized tungsten nanowires grew along [100] direction, with a high aspect ratio more than 50 and sharp tips. The Ni catalyst was found to be located at the wire's bottom and assisted the nucleation of the tungsten nanowire. Samples were characterized in detail by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) technologies. Based on the analysis of the experimental results, the possible formation mechanism of nanowires was proposed as well.

Synthesis and visible light photocatalytic activity of Mo–N codoped TiO2 nanowires prepared by amorphous titania spheres via hydrothermal process

Mo–N codoped TiO2 nanowires were synthesised through hydrothermal process. The physicochemical features of the nanowires were characterised by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectroscopy. Structural characterisation indicates that the Mo–N codoped TiO2 nanowires of a high purity with large aspect ratio were very thin. The photocatalytic activities of the nanowires were determined by degradation of methyl blue solution under visible light irradiation. At last, the possible formation mechanism of nanowires has simply been proposed on the basis of the SEM results.

ZnO Nanorod Arrays and Nanowires by Hydrothermal Growth

We are reporting here on an inexpensive and facile fabrication method for ZnO nanorod arrays by hydrothermal growth at low temperature (90°C). In our experiment, ZnO nanostructures were grown on glass substrate using an equimolar (0.1M) aqueous solution of Zn(NO3)2•6H2O (zinc nitrate hexahydrate) and C6H12N4 (HMTA) as precursors solution, and using ammonia solution to controlling the pH levels. It enable easily obtained arrayed ZnO nanorods on substrate, and nanowires which grown on nanorod arrays were identified after about 1 month in the air. The growth process of nanorods and the formation mechanism of nanowires were investigated.

Synthesis of Single-Crystalline Silicon Nitride (α-Si3N4) Nanowires with Controlled Diameters by Nitriding Cryomilled Nanocrystalline Silicon Powder

AbstractIn the present work, silicon nitride nanowires (SNNWs) have been synthesized via nitriding cryomilled nanocrystalline silicon powder. The silicon powder exhibits a fine polycrystalline structure after the cryomilling process, with an average grain size of 25 to 125 nm at various cryomilling times. The SNNWs that form after the nitridation of the cryomilled silicon powder exhibit single crystal structure and are 20 to 100 nm in diameter and ∼10 µm in length. The diameter of the nanowires is in agreement with the grain size of the cryomilled Si powder. Microstructural characterization reveals that the as-synthesized nanowires have a hexagonal structure and their primary growth direction is along the [0001] direction. The formation of the Si–N–Si bond during the cryomilling process, as investigated theoretically with density functional theory, promotes the subsequent synthesis of the α-Si3N4 nanowires. The mechanism for nanowire formation appears to be a vapor-solid (VS) reaction.

Controllable synthesis of pentagonal silver nanowires via a simple alcohol-thermal method

Pentagonal silver nanowires with diameters in range of 20–40 nm, and lengths up to ~ 10 µm were successfully synthesized via a simple and effective alcohol-thermal route. These nanowires were prepared by reducing silver nitrate in ethanol solution with dodecylamine which acted as complexing, reducing and capping agent. The molar ratio of dodecylamine to AgNO 3 played an important role in controlling aspect ratio of the products. Samples were characterized in detail by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) technologies. UV–vis absorption spectrum of the nanowires in solution has been taken to study their optical properties. Based on the analysis of the experimental results, the possible formation mechanism of nanowires was proposed as well.

Synthesis of α silicon nitride single-crystalline nanowires by nitriding cryomilled nanocrystalline silicon powder

Si3N4 nanowires (SNNWs) have been synthesized via a novel approach involving nitriding cryomilled nanocrystalline Si powder. The SNNWs formed consist of single-crystal α-Si3N4, and are 30–100 nm in diameter and ∼10 μm in length. The formation of the Si−N−Si bond during the cryomilling process, as investigated theoretically by density functional theory, promotes the subsequent synthesis of the α-Si3N4 nanowires. The mechanism for nanowire formation appears to be a vapor–solid reaction.

One-step template-free solution route for Cu(OH)2 nanowires

Cu(OH)2 nanowires with a diameter of 8–10 nm and lengths of tens of micrometers were fabricated in the basic solution by dropping simply NaOH solution into CuCl2 solution at ambient temperature. The formation mechanism of nanowires was discussed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the samples.

Preparation, characterization and formation mechanism of gallium oxide nanowires

Abstract Ga 2 O 3 nanowires were fabricated via vapor–solid process in ambient atmosphere using Ga and Ga 2 O 3 as starting materials without adding catalyst. The Ga 2 O 3 nanowires were found to be about 10–80 nm in diameter and several micrometers long. The formation mechanism of the nanowires was analyzed by differential scanning calorimeter and thermogravimetric analysis and found to be controlled by the vapor–solid (VS) growth mechanism. This synthetic method is simple and low cost, and could be extended to synthesize ZnO and In 2 O 3 nanowires.

Densely packed single-crystal Bi 2Fe 4O 9 nanowires fabricated from a template-induced sol–gel route

Densely packed single-crystal Bi 2Fe 4O 9 nanowires were successfully synthesized by a template-induced citrate-based sol–gel process. The structural properties of the nanowires were characterized using many techniques. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that Bi 2Fe 4O 9 nanowires possessed a uniform length and diameter, which were controlled by the thickness and the pore diameter of the applied porous anodic aluminum oxide (AAO) template, respectively. The results of X-ray diffraction (XRD) and the selected area electron diffraction (SAED) indicated that Bi 2Fe 4O 9 nanowires had an orthorhombic single-crystal structure. Furthermore, the energy-dispersive X-ray (EDX) spectroscopy demonstrated that the stoichiometric Bi 2Fe 4O 9 was formed. The possible formation mechanism of nanowires was also discussed.

Sol–gel template synthesis and characterization of LaCoO3 nanowires

Densely packed LaCoO3 nanowires of the rare-earth perovskite-type composite oxide were synthesized within a porous anodic aluminum oxide (AAO) template by means of the sol–gel method using nitrate as raw the material and citric acid as the chelating agent. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the LaCoO3 nanowires possessed a uniform length and diameter, which were controlled by the thickness and the pore diameter of the applied AAO template, respectively. The results of X-ray diffraction (XRD) and the selected area electron diffraction (SAED) indicated that the LaCoO3 nanowires had a rhombohedral perovskite-type crystal structure. Furthermore, X-ray photoelectron spectroscopy (XPS) demonstrated that LaCoO3 nanowires were formed. Finally, the formation mechanism of nanowires was also discussed.

Solvothermal synthesis and characterization of uniform CdS nanowires in high yield

Large-scale CdS nanowires with uniform diameter and high aspect ratios were synthesized using a simple solvothermal route that employed CdCl 2 and S powder as starting materials, ethylenediamine (en) as the solvent. X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) images show that the products are hexagonal structure CdS nanowires with diameter of 40 nm and length up to 10 μm. Selected area electron diffraction (SAED) and high resolution TEM (HRTEM) studies indicate the single-crystalline nature of CdS nanowires with an oriented growth along the c-axis direction. The optical properties of the products were characterized by optical absorption spectra and photoluminescence spectra. Based on the results of contrastive experiments, it is found that the sulfur source and the solvent play significant roles in the formation of uniform nanowires. A possible formation mechanism of nanowires is discussed.

Synthesis and characterization of single-crystalline nanowires of bismuth doped with manganese

We report the first synthesis of nanowires of bismuth doped with manganese prepared via an homogeneous non-aqueous solution reaction. By studying intermediates at different temperatures during the nanowire growth process, the evolution of the crystallization of metallic products and the mechanism of nanowire formation are investigated. In this work, a combination of TEM (transmission electron microscopy), XRD (X-ray powder diffractometry), ICP (inductively-coupled plasma spectrometer) and SQUID (superconducting quantum interference device) magnetometry were employed to characterize the morphology, structure, composition and magnetic properties of the products.