Template assisted synthesis of SnO<Subscript>2</Subscript> nanorods by immerse and filtration technique,vacuum and drop setting

Honeycomb-shaped and ordered arrays of nanopore AAO template with a uniform pores size was produced utilizing a two-step an anodization process. Highly ordered SnO₂ nanorods arrays have been selectively fabricated via a convenient (immerse and filtration) technique and (vacuum and drop) setting using anodic aluminum oxide (AAO) as a hard template. The morphology of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (FESEM), and Energy-dispersive X-ray spectroscopy (EDX) techniques. The optical characterizations were examined by UV-VIS and Photoluminescence (PL). Scanning microscopy images indicate that the SnO₂ nanorods are relatively uniform with the outer diameter matching well with the pore diameter. XRD and EDX indicated that these polycrystalline SnO₂ nanostructures with well-defined composition were obtained.     

Growth of vertically aligned InGaN nanorod arrays on p-type Si substrates for heterojunction diodes

InGaN nanorod arrays have been grown by molecular beam epitaxy on bare and high-temperature AIN-buffered Si(111) substrates. It has been found that well vertically aligned InGaN nanorod arrays can be grown by using the high-temperature AIN buffer layer. On bare Si substrate, high-resolution transmission electron microscopy revealed an amorphous SiNx layer generated at the interface, and the thickness and flatness of the SiNx layer may affect the relative alignment of the nanorods with the substrate. By using the high-temperature AIN buffer layer, the interface quality was improved, and uniform InGaN nanorods could be grown. N-InGaN nanorods/p-Si heterostructure diodes were fabricated, which exhibit well rectifying behavior with a low turn on voltage of 1.2 eV and an on/off ratio of 7.2 at 2.5 V.     

A simple solution route to controlled synthesis of ZnS submicrospheres, nanosheets and nanorods

ZnS nanostructures with different morphologies of submicrospheres, nanosheets and nanorods were synthesized by solution precipitation of thiourea with Zn(NO(3))(2) in the presence of block copolymer at low temperature. The sizes and morphologies of ZnS can be controlled simply by?changing the processing parameters. The results show that the ZnS submicrospheres are of 250-500?nm in diameter, nanosheets are 2.5?μm × 5.5?μm with an estimated thickness of 20-30?nm, and nanorods are 2-5?nm in diameter and 10-30?nm in length. Keeping the precursor system in an autoclave at 105?°C results in the formation of ZnS submicrospheres; ultrasonication and keeping the system at room temperature leads to the formation of ZnS nanosheets; and long-time continuous ultrasonication and keeping the system in an autoclave at 105?°C induces the formation of uniform ZnS nanorods. We argue that the reaction temperature and P123 may play crucial roles in the formation of three ZnS structures in this work. The morphologically controllable synthesis strategies may be extended to the shape-controlled production of nanostructures of other inorganic materials.     

Solvent induced formation of an ordered nanorod array of gold/polymer composite by block copolymer film templating

We report a novel method to fabricate ordered arrays of gold-polymer composite nanorods with the orientation in the vertical direction using block copolymer (BCP) film. The salt precursor is selectively infiltrated within vertically aligned cylindrical domains of the BCP film by immersing the template in a simple aqueous solution of HAuCl(4). Scanning electron microscopy suggests that the salt might be uniformly positioned along the polymeric cylinders. A subsequent vacuum ultraviolet light irradiation simultaneously reduces the HAuCl(4) into spherical gold nanoparticles with mean diameter around 2?nm and removes the matrix of the BCP template to produce metal-polymer composite nanorods. While the solvent is methanol, the salt might be concentrated at the bottom of the BCP film. As a result, a periodic pattern of gold nanoparticles with average diameter around 11?nm is formed where the BCP film is completely etched away. The solvent can effectively tune the spatial distribution of the salt precursor along the polymeric cylinders, which is responsible for the different morphologies of the photochemically fabricated nanostructures.     

Direct nanorod assembly using block copolymer-based supramolecules

Developing routes to control the organization of one-dimensional nanomaterials, such as nanorods, with high precision is critical to generate functional materials since the collective properties depend on their spatial arrangements, interparticle ordering, and macroscopic alignment. We have systematically investigated the coassemblies of nanorods and block copolymer (BCP)-based supramolecules and showed that the energetic contributions from nanorod ligand-polymer interactions, polymer chain deformation, and rod-rod interactions are comparable and can be tailored to disperse nanorods with control over inter-rod ordering and the alignment of nanorods within BCP microdomains. By varying the supramolecular morphology and chemical nature of the nanorods, two highly sought-after morphologies, that is, nanoscopic networks of nanorods and nanorod arrays parallel to cylindrical BCP microdomains can be obtained. The supramolecular approach can be applied to achieve morphological control in nanorod-containing nanocomposites toward fabrication of optical and electronic nanodevices.     

Highly aligned ultrahigh density arrays of conducting polymer nanorods using block copolymer templates

Ultrahigh density arrays of conducting polypyrrole (PPy) nanorods are fabricated directly on the indium-tin oxide coated glass by an electropolymerization within a porous diblock copolymer template. The nanorods are shown to have conductivity much higher than thin PPy films, due to the high degree of chain orientation, even though the separation distance for two neighboring PPy main chains is as small as 0.37 nm. The ultrahigh density arrays of conducting polymer nanorods have potential applications as sensor materials, nanoactuators, and organic photovoltaic devices.     

Growth of well-aligned ZnO nanorod arrays on Si substrates by thermal evaporation of Cu-Zn alloy powders

Well-aligned ZnO nanorod arrays with uniform diameters and lengths have been fabricated on a Si substrate by simple thermal evaporation of Cu-Zn alloy powders in the presence of oxygen without using a template, catalyst, or pre-deposited ZnO seed layer. The ZnO nanorods are characterized by X-ray diffraction, electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy and the growth mechanism is suggested. The nanorods have a single-crystal hexagonal structure and grow along the (0001) direction. Their diameters range from 200 to 400 nm and the lengths are up to several micrometers. The photoluminescence (PL) and Raman spectra disclose the optical properties of the products. The PL spectra show intense near-band ultraviolet emission at 378 nm from the nanorod arrays. The well-aligned ZnO nanorod arrays have a low turn-on field of 6.1 V/microm, suggesting good field emission properties. The simple synthesis methodology in conjunction with the good field emission and optical properties make the study both scientifically and technologically interesting.     

Silicon nano-well arrays for reliable pattern transfer and locally confined high temperature reactions

Si nano-well arrays, with precisely controlled undercut Si sidewall profiles and flat bottomed pockets, enable uniform nanoscale pattern transfer from resists to metal deposits without degradation of the initial lithographic resolution, as verified by the formation of arrays of Au nano-dots with 10 nm diameter. An additional functionality of the Si nano-wells as local nano-reactors, where the patterned material is enclosed in a Si pocket during high temperature reaction, is demonstrated by thermally inducing a phase transformation of the as-deposited A1 phase of FePt nano-dots to the high coercivity, chemically ordered L1(0) phase.     

Controllable growth of highly ordered ZnO nanorod arrays via inverted self-assembled monolayer template

This article presents a facile and effective approach to the controllable growth of highly ordered and vertically aligned ZnO nanorod arrays on the GaN substrate via a hydrothermal route by using the TiO(2) ring template deriving from the polystyrene microsphere self-assembled monolayer. The size of TiO(2) ring template can be flexibly tuned from 50 to 400 nm for the 500 nm polystyrene microspheres by varying the time of reactive ion etching and the concentration of TiO(2) sol. As a result, the diameter of the individual ZnO nanorods can be potentially tuned over a wide range. The combination of several characterization techniques has demonstrated that the ordered ZnO nanorods are highly uniform in diameter and height with perfect alignment and are epitaxially grown along [0001] direction. This work provides a novel and accessible route to prepare oriented and aligned ZnO nanorod arrays with high crystalline quality.     

镍纳米管阵列的电沉积合成及其磁学性能表征

以氧化铝膜为模板、金属汞为电阴极,采用简单的直流电沉积方法制备出高度有序的镍纳米管阵列。利用扫描电子显微镜、透射电子显微镜、选区电子衍射、能谱仪、X射线粉末衍射和样品振动磁强计对样品进行形貌表征、成分及磁性能分析。结果表明,阵列中的镍纳米管彼此平行,尺寸均匀,纳米管外径为260～360nm;镍纳米管阵列表现出良好的磁各向异性,其易磁化方向垂直于镍纳米管阵列。以金属汞为电阴极是易形成纳米管的关键条件。     

Defect induced room temperature ferromagnetism in well-aligned ZnO nanorods grown on Si (100) substrate

In this work, we report the fabrication of high quality single-crystalline ZnO nanorod arrays which were grown on the silicon (Si) substrate using a microwave assisted solution method. The as grown nanorods were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photo-luminescence (PL) and magnetization measurements. The XRD results indicated that the ZnO nanorods are well oriented with the c-axis perpendicular to the substrate and have single phase nature with the wurtzite structure. FE-SEM results showed that the length and diameter of the well aligned rods is about ~ 1 μm and ~ 100 nm respectively, having aspect ratio of 20-30. Room-temperature PL spectrum of the as-grown ZnO nanorods reveals a near-band-edge (NBE) emission peak and defect induced green light emission. The green light emission band at ~ 583 nm might be attributed to surface oxygen vacancies or defects. Magnetization measurements show that the ZnO nanorods exhibit room temperature ferromagnetism which may result due to the presence of defects in the ZnO nanorods.     

Vapor-phase synthesis of aligned zinc oxide nanorod arrays on various substrates

Zinc oxide nanorod arrays have been grown on Si(100), Si(111), and glass substrates by low-pres-sure chemical vapor deposition from elemental zinc and oxygen. Under the experimental conditions of this study, nanorods grow along the c-axis and are predominantly normal to the substrate surface, independent of the crystallographic orientation of the substrate. The cathodoluminescence spectra of all the samples obtained show one strong emission band in the UV spectral region, due to free-exciton recombination, which attests to good stoichiometry of the ZnO nanocrystals. The uniformity of the arrays correlates with the density of nanorods per unit area and their thickness.     

Morphology effect on the performances of SnO2 nanorod arrays as anodes for Li-ion batteries

Ni foam suppported-SnO₂ nanorod arrays with controllable diameter were prepared via a template-free growth method, which was a convenient route for the large-scale growth of pure-phase metal oxide nanorod arrays on metal substrates. The relationship between electrochemical behavior and the shape of SnO₂ nanorod arrays has been investigated in detail. SnO₂ nanorod arrays with diameter of about 25 nm, as anode materials for Li-ion batteries revealed a capacity of 607 mAh g⁻¹ (at 0.2 C) up to 50 cycles. The superior performance of the SnO₂ nanorods can be mainly attributed to small size of nanorods which reduce volume expansion and lithium diffusion length.     

A method to fabricate nanorod films on aluminum lattice membrane by magnetron sputtering

The development of the process of fabricating well-aligned nanostructures materials is one of the interesting subjects in current material science. This paper describes a new method to fabricate high-density, vertically-aligned nanorods of metal and metal compound by magnetron sputtering on aluminum lattice membrane (ALM). The ALM was formed by chemical etching of the hexagonal arrays of pore layer from the anodic aluminum oxide membrane, resulting in unnumbered hemisphere nanopits with uniform protuberant nanodots on the surface of aluminum. The ALM was employed as a substrate to fabricate well-aligned Ni, Cu, WC nanorod films by magnetron sputtering. Scanning electron microscopy images showed that the sputtered atoms have been absorbed preferentially onto the protuberant nanodots of ALM in the process of magnetron sputtering, and have begun to nucleate and grow into nanorods. The diameter of the nanorods depends on the diameter of hemisphere on the surface of the substrate, while the thickness of thin films can be controlled by deposition time.     

Growth of well-aligned ZnO nanorods using auge catalyst by vapor phase transportation

Well-aligned ZnO nanorods have been achieved using new alloy (AuGe) catalyst. Zn powder was used as a source material and it was transported in a horizontal tube furnace onto an AuGe deposited Si substrates. The structural and optical properties of ZnO nanorods were characterized by scanning electron microscopy, high resolution X-ray diffraction, and photoluminescence. ZnO nanorods grown at 650 degrees C on 53 nm thick AuGe layer show uniform shape with the length of 8 +/- 0.5 microm and the diameter of 150 +/- 5 nm. Also, the tilting angle of ZnO nanorods (+/- 5.5 degrees) is confirmed by HRXRD. High structural quality of the nanorods is conformed by the photoluminescence measurement. All samples show strong UV emission without considerable deep level emission. However, weak deep level emission appears at high (700 degrees C) temperature due to the increase of oxygen desertion.     

Silicon nanorods prepared by glancing angle catalytic chemical vapor deposition

Vertically oriented amorphous and microcrystalline Si nanorods grown on different substrates were successfully obtained by Cat CVD with the glancing angle incident silane flux at low temperatures. The influences of the substrate type, substrate temperature, post treatment and hydrogen dilution on the microstructure of Si nanorods were investigated. The density and diameter of nanorods are varying with the substrates. The hydrogen dilution of silane dominates the crystallization of Si nanorods rather than high substrate temperature at 550 °C and annealing at 900 °C in nitrogen for 6 h. The crystallized Si nanorods with crystalline volume fraction, Xc, of 0.55 were achieved under a low substrate temperature of 140 °C.     

Optical properties of GaN nanorods grown by molecular-beam epitaxy; dependence on growth time

The growth and optical properties of GaN nanorods grown on Si(111) substrates by rf plasma assisted molecular-beam epitaxy are investigated by means of field emission scanning electron microscopy and photoluminescence measurements as a function of growth time. It is clearly demonstrated that the rate of growth of the nanorod diameter starts to increase after ～90?min because of the coalescence of neighbouring nanorods. And the optical properties of the samples grown at a high growth rate are dramatically changed due to induced defects. The critical diameter for defect-free GaN nanorods is determined as below ～140?nm under N-rich conditions.     

Fabrication of free-standing Cu nanorod arrays on Cu disc by template-assisted electrodeposition

Free-standing Cu nanorod arrays on Cu foil have been fabricated by a template-assisted method. Cu nanorods were potentiostatically deposited on mechanically polished Cu foil using anodized aluminum oxide templates as the deposition mask. Three electrolyte systems were compared, including two acid copper sulfate based solutions and one alkaline solution. The most uniform nanorods were achieved in the alkaline electrolyte. The weight gain per unit area after electrodeposition has been used as a direct measure of average length of deposited Cu nanorods. It was found that our control over the uniformity in nanorod length across the array is important in reaching the maximized aspect ratio without aggregation. Through controlling the weight change it was possible to control the aspect ratio of nanorods and to avoid aggregation of nanorods. Our capability to fabricate free-standing Cu nanorod arrays of uniform height with maximized aspect ratio on Cu foil is especially important in applying this nanostructured Cu as a current collector in Li ion batteries.     

Synthesis, characterization, and optical properties of ordered arrays of III-nitride nanocrystals

A new approach involving self-assembling block copolymer micellar templates and gas-phase reactions to synthesize arrays of monodisperse III-nitrides nanocrystals in the size range of 1-5 nm with uniform spacings between the nanoparticles is demonstrated. The photoluminescence emission spectra revealed the GaN nanocrystals are in the quantum-confined regime. This method not only offers great promise for the controlled synthesis of arrays of ternary III-nitride nanocrystals but may also enable doping in binary nitrides.     

Fabrication of nanostructure and formation of nanocrystal for non-volatile memory

In this work, we have demonstrated that the nanocrystal created by combining the self-assembled block copolymer thin film with regular semiconductor processing can be applicable to non-volatile memory device with increased charge storage capacity over planar structures. Self-assembled block copolymer thin film for nanostructures with critical dimensions below photolithographic resolution limits has been used during all experiments. Nanoporous thin film from PS-b-PMMA diblock copolymer thin film with selective removal of PMMA domains was used to fabricate nanostructure and nanocrystal. We have also reported about surface morphologies and electrical properties of the nano-needle structure formed by RIE technique. The details of nanoscale pattern of the very uniform arrays using RIE are presented. We fabricated different surface structure of nanoscale using block copolymer. We also deposited Si-rich SiNx layer using ICP-CVD on the silicon surface of nanostructure. The deposited films were studied after annealing. PL studies demonstrated nanocrystal in Si-rich SiNx film on nanostructure of silicon.