Fabrication of Ni-silicide/Si heterostructured nanowire arrays by glancing angle deposition and solid state reaction

This work develops a method for growing Ni-silicide/Si heterostructured nanowire arrays by glancing angle Ni deposition and solid state reaction on ordered Si nanowire arrays. Samples of ordered Si nanowire arrays were fabricated by nanosphere lithography and metal-induced catalytic etching. Glancing angle Ni deposition deposited Ni only on the top of Si nanowires. When the annealing temperature was 500°C, a Ni₃Si₂ phase was formed at the apex of the nanowires. The phase of silicide at the Ni-silicide/Si interface depended on the diameter of the Si nanowires, such that epitaxial NiSi₂ with a {111} facet was formed at the Ni-silicide/Si interface in Si nanowires with large diameter, and NiSi was formed in Si nanowires with small diameter. A mechanism that is based on flux divergence and a nucleation-limited reaction is proposed to explain this phenomenon of size-dependent phase formation.     

Large-scale fabrication of ordered arrays of microcontainers and the restraint effect on growth of CuO nanowires

Technique has been developed to fabricate ordered arrays of microcontainers. We report that ordered microcontainer arrays of Cu can be fabricated on glass substrate by thin film deposition and self-assembly technology. In addition, CuO nanowires are found to grow only in the inner sides of microcontainers, which verifies the stress growth mechanism of CuO nanowires. High-resolution transmission electron microscopy study reveals that CuO nanowires grow along the [110] direction. Such structure may have potential application in micro-electron sources, which have the self-focused function.     

Tuning the microstructure and functional properties of metal nanowire arrays via deposition potential

The present study is focused on electrochemical fabrication and characterization of the ordered arrays of one-dimensional Ni nanostructures templated by porous anodic alumina films. A possibility to monitor and control homogeneity of arrays and completeness of the pores filling in the course of potentiostatic deposition is discussed. Current efficiency is determined from independent analytical data and taken into account in the treatment of charge transients. The crystallinity of Ni nanowire arrays as well as the homogeneity and completeness of the replication process are demonstrated to be controlled by deposition potential. Just these structural features affect the magnetic properties of nanowire arrays. The advantages and drawbacks of the quantitative coulometric analysis of current transients are considered.     

Lithographically patterned micro-/nanostructures via colloidal lithography

Colloidal lithography is an effective and facile strategy for highly ordered nanostructure arrays that is a simple, inexpensive, and high-throughput process with a broad choice of materials in manufacturing various lithographically patterned nanostructures on substrates. To develop such nanostructured systems, various nanofabrication techniques are employed on two-dimensional (2D) colloidal masks for evaporation, electrochemical deposition, etching, dewetting and mask replication. Ordered nanostructures associated with feature shapes and sizes can be diversified through a choice of methodology and a control of experimental conditions. This review presents an overview of colloidal crystals as a mask and nanostructure arrays (nanopillars, nanoring, nanopores) fabricated by colloidal lithography as well as introducing practical applications using ordered nanostructures.     

New Colloidal Lithographic Nanopatterns Fabricated by Combining Pre-Heating and Reactive Ion Etching

We report a low-cost and simple method for fabrication of nonspherical colloidal lithographic nanopatterns with a long-range order by preheating and oxygen reactive ion etching of monolayer and double-layer polystyrene spheres. This strategy allows excellent control of size and morphology of the colloidal particles and expands the applications of the colloidal patterns as templates for preparing ordered functional nanostructure arrays. For the first time, various unique nanostructures with long-range order, including network structures with tunable neck length and width, hexagonal-shaped, and rectangular-shaped arrays as well as size tunable nanohole arrays, were fabricated by this route. Promising potentials of such unique periodic nanostructures in various fields, such as photonic crystals, catalysts, templates for deposition, and masks for etching, are naturally expected.     

A hydrogen peroxide electrochemical sensor based on silver nanoparticles decorated silicon nanowire arrays

The ordered H-terminated Si nanowire (SiNW) arrays via electroless etching method are capable of reducing silver ions, leading to the deposition of Ag nanoparticles (AgNPs) on SiNW. The AgNPs decorated SiNW arrays are directly fabricated into a novel sensor for the detection of hydrogen peroxide in phosphate buffered solutions. The results of electrochemical experiments reveal that such constructed sensor has a fast amperometric sensing, low detection limit and wide linear responding range as well as high sensitivity. Our results indicate that the AgNPs decorated SiNW arrays with favorable electrocatalytic performance are very promising for the future development of non-enzymatic hydrogen peroxide sensors.     

Synthesis and Growth Mechanism of Ni Nanotubes and Nanowires

Highly ordered Ni nanotube and nanowire arrays were fabricated via electrodeposition. The Ni microstructures and the process of the formation were investigated using conventional and high-resolution transmission electron microscope. Herein, we demonstrated the systematic fabrication of Ni nanotube and nanowire arrays and proposed an original growth mechanism. With the different deposition time, nanotubes or nanowires can be obtained. Tubular nanostructures can be obtained at short time, while nanowires take longer time to form. This formation mechanism is applicable to design and synthesize other metal nanostructures and even compound nanostuctures via template-based electrodeposition.     

Fabrication,modification and environmental applications of TiO2 nanotube arrays (TNTAs) and nanoparticles

Among the semiconductors, titanium dioxide has been identified as an effective photocatalyst due to its abundance, low cost, stability, and superior electronic energy band structure. Highly ordered nanotube arrays of titania were produced by anodization and mild sonication. The band gap energy of the titania nanotube arrays was reduced to 2.6 eV by co-doping with Fe, C, N atoms using an electrolyte solution containing K₃Fe(CN)₆. The photoconversion of phenol in a batch photoreactor increased to more than 18% based on the initial concentration of phenol by using a composite nanomaterial consisting of titania nanotube arrays and Pt/ZIF-8 nanoparticles. A layer-by-layer assembly technique for the deposition of titania nanoparticles was developed to fabricate air filters for the degradation of trace amounts of toluene in the air and preparation of superhyrophobic surfaces for oil-water separation and anti-corrosion surfaces.     

Growth of arrays of oriented epitaxial platinum nanoparticles with controlled size and shape by natural colloidal lithography

We developed a method for production of arrays of platinum nanocrystals of controlled size and shape using templates from ordered silica bead monolayers. Silica beads with nominal sizes of 150 and 450 nm were self-assembled into monolayers over strontium titanate single crystal substrates. The monolayers were used as shadow masks for platinum metal deposition on the substrate using the three-step evaporation technique. Produced arrays of epitaxial platinum islands were transformed into nanocrystals by annealing in a quartz tube in nitrogen flow. The shape of particles is determined by the substrate crystallography, while the size of the particles and their spacing are controlled by the size of the silica beads in the monolayer mask. As a proof of concept, arrays of platinum nanocrystals of cubooctahedral shape were prepared on (100) strontium titanate substrates. The nanocrystal arrays were characterized by atomic force microscopy, scanning electron microscopy, and synchrotron X-ray diffraction techniques.     

Characterization and Optical Properties of the Single Crystalline SnS Nanowire Arrays

The SnS nanowire arrays have been successfully synthesized by the template-assisted pulsed electrochemical deposition in the porous anodized aluminum oxide template. The investigation results showed that the as-synthesized nanowires are single crystalline structures and they have a highly preferential orientation. The ordered SnS nanowire arrays are uniform with a diameter of 50 nm and a length up to several tens of micrometers. The synthesized SnS nanowires exhibit strong absorption in visible and near-infrared spectral region and the direct energy gap E _g of SnS nanowires is 1.59 eV.     

Photolithographic Approaches for Fabricating Highly Ordered Nanopatterned Arrays

In this work, we report that large area metal nanowire and polymer nanotube arrays were successfully patterned by photolithographic approach using anodic aluminum oxide (AAO) templates. Nanowires were produced by electrochemical deposition, and nanotubes by solution-wetting. The highly ordered patterns of nanowire and nanotube arrays were observed using scanning electron microscopy (SEM) and found to stand free on the substrate. The method is expected to play an important role in the application of microdevices in the future.     

Sub-100-nm ordered silicon hole arrays by metal-assisted chemical etching

Sub-100-nm silicon nanohole arrays were fabricated by a combination of the site-selective electroless deposition of noble metals through anodic porous alumina and the subsequent metal-assisted chemical etching. Under optimum conditions, the formation of deep straight holes with an ordered periodicity (e.g., 100 nm interval, 40 nm diameter, and high aspect ratio of 50) was successfully achieved. By using the present method, the fabrication of silicon nanohole arrays with 60-nm periodicity was also achieved.     

直流电沉积二元合金Co55Ni45纳米棒阵列及其表征

引言 一维金属及合金纳米材料由于其纳米尺寸产生的小尺寸效应、表面效应、量子尺寸效应及宏观量子隧道效应导致与常规金属及合金材料迥然不同的热、磁、光、电、敏感特性和表面稳定性,有望在纳机电系统(NEMS)、光吸收过滤器和调制器、垂直磁记录材料和巨磁阻材料、催化剂等领域取得重大突破.人们采取许多种方法进行一维金属及合金纳米材料的合成及性能研究.很多研究者以含有纳米微孔的聚碳酸酯过滤膜或多孔氧化铝膜为模板合成了Au[1]、Cu[2]、Pd[2]、Ag[3]、Fe[4]、Co[5]、CoFe[5]、Ni[6]等一维纳米线,Liu[7]在钼网上气相沉积了Cu纳米棒和纳米线,Xiong等[8]利用二茂铁的夹层结构,还原制备了银纳米线,Yen[9]利用氯化亚铜与二甲基硅氧烷聚合物胶囊材料合成了铜纳米线等,姚素薇等[10]在单晶硅上脉冲电沉积制备了Cu/Co纳米多层膜.相对于单一金属而言,合金由两种及两种以上金属组成而具有多种金属复合性能,因此更具有研究与应用价值,但目前对合金类一维纳米材料的研究还较少.本文以聚碳酸酯膜为模板,利用直流电沉积的方法制备出二元合金Co55Ni45纳米棒阵列结构材料,实验在双电极体系下进行,方法简单,所制备的Co55Ni45合金纳米棒阵列呈锥状结构且整齐排列,可用作垂直磁记录材料及原子力显微镜探针材料.     

Fabrication of dye-sensitized solar cells using ordered and vertically oriented TiO2 nanotube arrays with open and closed ends

Highly ordered and vertically oriented TiO₂ nanotube arrays were prepared and applied to dye sensitized solar cell (DSSC) as working electrodes. The nanotube arrays were fabricated using atomic layer deposition and AAO template. The two types of nanotube's end, closed-end and open-end, were produced by reactive ion etching (RIE) process. The structure of nanotube arrays was characterized by FE-SEM, TEM, and XRD. DSSCs using the TiO₂ nanotube arrays as working electrodes were fabricated and characterized. The DSSCs prepared from the TiO₂ nanotubes with open end exhibited higher power conversion efficiency of 1.17% than that with closed end. This result is attributed to that the open-ended TiO₂ nanotubes provided larger surface area, leading to more amount of dye molecules to adsorb followed by the higher light absorption.     

Triangle pore arrays fabricated on Si (111) substrate by sphere lithography combined with metal-assisted chemical etching and anisotropic chemical etching

ABSTRACT: The morphological change of silicon macropore arrays formed by metal-assisted chemical etching using shape-controlled Au thin film arrays was investigated during anisotropic chemical etching in tetramethylammonium hydroxide (TMAH) aqueous solution. After the deposition of Au as the etching catalyst on (111) silicon through a honeycomb mask prepared by sphere lithography, the specimens were etched in a mixed solution of HF and H2O2 at room temperature, resulting in the formation of ordered macropores in silicon along the [111] direction, which is not achievable by conventional chemical etching without a catalyst. In the anisotropic etching in TMAH, the macropores changed from being circular to being hexagonal and finally to being triangular owing to the difference in etching rate between the crystal planes.     

汽车尾气净化催化剂载体-纳米氧化铝模板的自组织行为研究

本文探索了在草酸和硫酸电解液中，铝阳极氧化自组织有序纳米六方结构氧化铝的条件。研究发现，在两种酸中铝箔均可氧化得到高度有序的六方孔阵，其有序区域的尺寸与施加的外电压和电流效率有关。并提出了金属铝箔与形成的氧化铝界面间的机械应力是由于相邻孔间产生排斥力的原因所在，这种排斥和的存在促进了其有序孔阵的形成。     

Two-dimensional ZnO-NiO macroporous arrays: Fabrication, structure and electrical properties

Colloidal templating and pulsed laser deposition were combined to fabricate arrays of ordered two-dimensional macroporous ZnO-NiO thin films. The underlying principles involved in the formation of colloidal templates were investigated using Fourier transformations and radial distribution functions. The macroporous thin film consists of hollow half-spheres of nanocrystalline wurtzite ZnO and rock salt NiO. The electrical properties of macroporous ZnO-NiO thin films were investigated by impedance and DC current-voltage measurements. The electrical properties are controlled by the interfaces between oxide grains. The potential applications such as gas sensors and optics are discussed.     

Fabrication of Highly Ordered Polymeric Nanodot and Nanowire Arrays Templated by Supramolecular Assembly Block Copolymer Nanoporous Thin Films

Realizing the vast technological potential of patternable block copolymers requires both the precise controlling of the orientation and long-range ordering, which is still a challenging topic so far. Recently, we have demonstrated that ordered nanoporous thin film can be fabricated from a simple supramolecular assembly approach. Here we will extend this approach and provide a general route to fabricate large areas of highly ordered polymeric nanodot and nanowire arrays. We revealed that under a mixture solvent annealing atmosphere, a near-defect-free nanoporous thin film over large areas can be achieved. Under the direction of interpolymer hydrogen bonding and capillary action of nanopores, this ordered porous nanotemplate can be properly filled with phenolic resin precursor, followed by curation and pyrolysis at middle temperature to remove the nanotemplate, a perfect ordered polymer nanodot arrays replication was obtained. The orientation of the supramolecular assembly thin films can be readily re-aligned parallel to the substrate upon exposure to chloroform vapor, so this facile nanotemplate replica method can be further extend to generate large areas of polymeric nanowire arrays. Thus, we achieved a successful sub-30 nm patterns nanotemplates transfer methodology for fabricating polymeric nanopattern arrays with highly ordered structure and tunable morphologies.     

Nanostructured materials prepared by use of ordered porous alumina membranes

We report on three different methods to prepare nanostructured materials using highly ordered porous alumina membranes as templates: (1) firstly, a new and simple method, termed as the paired cell method, was developed for the preparation of inorganic nanowires. Several kinds of inorganic nanowires were synthesized using this method. The structure and composition of these nanowires were determined by field emission scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. (2) Secondly, highly ordered platinum nanowire arrays were prepared by electrochemical method with the help of porous alumina membrane templates. The structure and composition of these nanowire arrays were also characterized by various experimental techniques. The electrochemically active surface area of the nanowire arrays was determined by cyclic voltammetry based on hydrogen adsorption. Results showed that the platinum nanowire arrays exhibited a large surface area. (3) Finally, we also present a simple and reliable procedure for the preparation of highly ordered metal nanohole and nanopillar arrays, based on the anodic oxidation of aluminum and vacuum evaporation technology. The field emission scanning electron microscopic images revealed that these metal nanostructure arrays were highly ordered over a large area. The nanoimprinting of aluminum surfaces using the as-prepared chromium nanopillar arrays was demonstrated, resulting in periodic indentation on the aluminum surface.     

Spatial Variations in the Sintering Rate of Ordered and Disordered Particle Structures

Local sintering rates were measured in two-dimensional, ordered and disordered structures constructed from glass spheres. In ordered arrays, made from monosized spheres, the local sintering rates varied from 1/2 to 2 times the average sintering rate. In contrast, disordered arrays, made from bimodal particle sizes, sintered more homogeneously, the local sintering rate deviating less than 15% from the average. The total average densification strain was also greater for the disordered structures. As a result, for the same time and temperature cycle, the disordered structures sintered to near full density while the ordered structures did not. Poor densification in the ordered structure was attributed to packing defects such as domain walls and dislocations. Some evidence was obtained for a correlation between densification and the average coordination number of particles.