钨晶须/纳米线的制备工艺原理及最新研究进展

综述了钨晶须/纳米线几种典型的制备方法及其最新研究进展,如气相沉积法、金属催化诱导法、电化学蚀刻法、模板法等,介绍了气-固、气-液-固和气-固-固生长机制及模型,分析了钨晶须/纳米线在研究和应用中存在的主要问题,指出钨晶须/纳米线生长过程中的影响因素、生长模型建立及钨晶须/纳米线的形貌、组成和产率综合调控是未来重要的研究方向.     

Advancements in Copper Nanowires: Synthesis,Purification, Assemblies,Surface Modification,and Applications

Copper nanowires (CuNWs) are attracting a myriad of attention due to their preponderant electric conductivity, optoelectronic and mechanical properties, high electrocatalytic efficiency, and large abundance. Recently, great endeavors are undertaken to develop controllable and facile approaches to synthesize CuNWs with high dispersibility, oxidation resistance, and zero defects for future large‐scale nano‐enabled materials. Herein, this work provides a comprehensive review of current remarkable advancements in CuNWs. The Review starts with a thorough overview of recently developed synthetic strategies and growth mechanisms to achieve single‐crystalline CuNWs and fivefold twinned CuNWs by the reduction of Cu(I) and Cu(II) ions, respectively. Following is a discussion of CuNW purification and multidimensional assemblies comprising films, aerogels, and arrays. Next, several effective approaches to protect CuNWs from oxidation are highlighted. The emerging applications of CuNWs in diverse fields are then focused on, with particular emphasis on optoelectronics, energy storage/conversion, catalysis, wearable electronics, and thermal management, followed by a brief comment on the current challenges and future research directions. The central theme of the Review is to provide an intimate correlation among the synthesis, structure, properties, and applications of CuNWs.     

One-dimensional nanostructures of ferroelectric perovskites

Nanorods, nanowires, and nanotubes of ferroelectric perovskites have recently been studied with increasing intensity due to their potential use in non-volatile ferroelectric random access memory, nano-electromechanical systems, energy-harvesting devices, advanced sensors, and in photocatalysis. This Review summarizes the current status of these 1D nanostructures and gives a critical overview of synthesis routes with emphasis on chemical methods. The ferroelectric and piezoelectric properties of the 1D nanostructures are discussed and possible applications are highlighted. Finally, prospects for future research within this field are outlined.     

Structural properties of <111>B -oriented III-V nanowires

Controlled growth of nanowires is an important, emerging research field with many applications in, for example, electronics, photonics, and life sciences. Nanowires of zinc blende crystal structure, grown in the <111>B direction, which is the favoured direction of growth, usually have a large number of twin-plane defects. Such defects limit the performance of optoelectronic nanowire-based devices. To investigate this defect formation, we examine GaP nanowires grown by metal-organic vapour-phase epitaxy. We show that the nanowire segments between the twin planes are of octahedral shape and are terminated by {111} facets, resulting in a microfaceting of the nanowires. We discuss these findings in a nucleation context, where we present an idea on how the twin planes form. This investigation contributes to the understanding of defect formation in nanowires. One future prospect of such knowledge is to determine strategies on how to control the crystallinity of nanowires.     

Titanium-assisted growth of silica nanowires: from surface-matched to free-standing morphologies

We report on an oxide-assisted growth technique for silica nanowires which allows tuning the growth from surface-matched nanowires to free-standing morphologies based on growth control by Ti in the role of a catalyst and surfactant. Using an adjustable Ti concentration, we grew silica nanowires with lengths ranging from 100 nm up to several millimetres whose defect chemistry was analysed by electron microscopy tools, monochromatic cathodoluminescence imaging and time resolved photoluminescence spectroscopy. The knowledge of the luminescence properties and the related defect occurrence along with their spatial distribution is pivotal for advancing silica nanowire growth in order to realize successful device designs based on self-assembled Si/SiO(x) nanostructures. We demonstrate a core-shell structure of the grown nanowires with a highly luminescent 150 nm thick shell and outstandingly fast decaying dynamics (≈1 ns) for glass-like materials. The conjunction of the observed efficient and stable luminescences with their attributed decaying behaviours suggests applications for silica nanowires such as active and passive optical interconnectors and white light phosphors. The identification of a time domain difference for the spectral regime from 2.3 to 3.3 eV, within the confined spatial dimensions of a single nanowire, is very promising for future, e.g. data transmission applications, employing silica nanowires which exhibit achievable compatibility with commonly applied silicon-based electronics. A qualitative growth model based on silica particle diffusion and Ti-assisted seed formation is developed for the various types of segregated silica nanowires which extends commonly assumed oxide-assisted growth mechanisms.     

Edge‐Epitaxial Growth of InSe Nanowires toward High‐Performance Photodetectors

Semiconducting nanowires offer many opportunities for electronic and optoelectronic device applications due to their unique geometries and physical properties. However, it is challenging to synthesize semiconducting nanowires directly on a SiO₂/Si substrate due to lattice mismatch. Here, a catalysis‐free approach is developed to achieve direct synthesis of long and straight InSe nanowires on SiO₂/Si substrates through edge‐homoepitaxial growth. Parallel InSe nanowires are achieved further on SiO₂/Si substrates through controlling growth conditions. The underlying growth mechanism is attributed to a selenium self‐driven vapor–liquid–solid process, which is distinct from the conventional metal‐catalytic vapor–liquid–solid method widely used for growing Si and III–V nanowires. Furthermore, it is demonstrated that the as‐grown InSe nanowire‐based visible light photodetector simultaneously possesses an extraordinary photoresponsivity of 271 A W^?1, ultrahigh detectivity of 1.57 × 10¹⁴ Jones, and a fast response speed of microsecond scale. The excellent performance of the photodetector indicates that as‐grown InSe nanowires are promising in future optoelectronic applications. More importantly, the proposed edge‐homoepitaxial approach may open up a novel avenue for direct synthesis of semiconducting nanowire arrays on SiO₂/Si substrates.     

AlN nanowires: synthesis, physical properties, and nanoelectronics applications

One-dimensional aluminum nitride (AlN) nanostructures, especially AlN nanowires, have been subjected to numerous investigations due to their unique physical properties and applications ranging from electronics to biomedical. This article reviews the synthesis of AlN nanowires and studies their physical properties and potential nanoelectronics applications. First, the different fabrication techniques used to synthesize AlN nanowires and their growth mechanisms are discussed. Next, the physical properties of AlN nanowires, such as the field emission, transport, photoluminescence, as well as the mechanical and piezoelectric properties are summarized. Finally, the potential applications of AlN nanowires in the field of nanoelectronics are described. Furthermore, this review summarizes the perspectives and outlooks on the future development of AlN nanowires.     

制备几种典型复合纳米线的相关实验及其分析

近年来,复合纳米线的制备成为低维纳米结构研究的一个热点.综述了几种典型复合纳米线的生长方法,分析了它们的生长机制,以及影响它们生长的各种因素.希望通过这几个制备复合纳米线的实验的分析与研究能对相关实验研究工作提供一些参考.     

Engineering III–V Semiconductor Nanowires for Device Applications

III–V semiconductor nanowires offer potential new device applications because of the unique properties associated with their 1D geometry and the ability to create quantum wells and other heterostructures with a radial and an axial geometry. Here, an overview of challenges in the bottom-up approaches for nanowire synthesis using catalyst and catalyst-free methods and the growth of axial and radial heterostructures is given. The work on nanowire devices such as lasers, light emitting nanowires, and solar cells and an overview of the top-down approaches for water splitting technologies is reviewed. The authors conclude with an analysis of the research field and the future research directions.     

生长温度对InAs/GaAs横向异质结构纳米线形貌及晶体结构的影响

低维半导体材料因其超常的物理性能而受到了广泛关注和研究。本文采用金属有机物化学气相沉积（MOCVD）技术,利用金作催化剂制备了InAs/GaAs横向异质结构纳米线,并讨论了不同生长温度情况下InAs横向异质材料对纳米线形貌及晶体结构的影响。提高InAs材料的生长温度,可以有效地抑制纳米线的纵向生长,使其实现横向异质结构的生长。在异质结构纳米线横向生长时发生了侧面晶面旋转的现象,这是纳米线表面重构后侧面趋向能量更低的晶面的结果。本文的研究工作为推动微纳技术的发展提供了相应的理论基础和科学依据。      

Synthesis, contact printing, and device characterization of Ni-catalyzed, crystalline InAs nanowires

InAs nanowires have been actively explored as the channel material for high performance transistors owing to their high electron mobility and ease of ohmic metal contact formation. The catalytic growth of nonepitaxial InAs nanowires, however, has often relied on the use of Au colloids which is non-CMOS compatible. Here, we demonstrate the successful synthesis of crystalline InAs nanowires with high yield and tunable diameters by using Ni nanoparticles as the catalyst material on amorphous SiO2 substrates. The nanowires show superb electrical properties with field-effect electron mobility ~2700 cm2/Vs and ION/IOFF >103. The uniformity and purity of the grown InAs nanowires are further demonstrated by large-scale assembly of parallel arrays of nanowires on substrates via the contact printing process that enables high performance, “printable” transistors, capable of delivering 5 10 mA ON currents (~400 nanowires).     

On-nanowire spatial band gap design for white light emission

We demonstrated a substrate-moving vapor-liquid-solid (VLS) route for growing composition gradient ZnCdSSe alloy nanowires. Relying on temperature-selected composition deposition along their lengths, single tricolor ZnCdSSe alloy nanowires with engineerable band gap covering the entire visible range were obtained. The photometric property of these tricolor nanowires, which was determined by blue-, green-, and red-color emission intensities, can be in turn controlled by their corresponding emission lengths. More particularly, under carefully selected growth conditions, on-nanowire white light emission has been achieved. Band-gap-engineered semiconductor alloy nanowires demonstrated here may find applications in broad band light absorption and emission devices.     

Ledge-flow-controlled catalyst interface dynamics during Si nanowire growth

Self-assembled nanowires offer the prospect of accurate and scalable device engineering at an atomistic scale for applications in electronics, photonics and biology. However, deterministic nanowire growth and the control of dopant profiles and heterostructures are limited by an incomplete understanding of the role of commonly used catalysts and specifically of their interface dynamics. Although catalytic chemical vapour deposition of nanowires below the eutectic temperature has been demonstrated in many semiconductor-catalyst systems, growth from solid catalysts is still disputed and the overall mechanism is largely unresolved. Here, we present a video-rate environmental transmission electron microscopy study of Si nanowire formation from Pd silicide crystals under disilane exposure. A Si crystal nucleus forms by phase separation, as observed for the liquid Au-Si system, which we use as a comparative benchmark. The dominant coherent Pd silicide/Si growth interface subsequently advances by lateral propagation of ledges, driven by catalytic dissociation of disilane and coupled Pd and Si diffusion. Our results establish an atomistic framework for nanowire assembly from solid catalysts, relevant also to their contact formation.     

Compared growth mechanisms of Zn-polar ZnO nanowires on O-polar ZnO and on sapphire

Controlling the growth of zinc oxide nanowires is necessary to optimize the performance of nanowire-based devices such as photovoltaic solar cells, nano-generators, or light-emitting diodes. With this in mind, we investigate the nucleation and growth mechanisms of ZnO nanowires grown by metalorganic vapor phase epitaxy either on O-polar ZnO or on sapphire substrates. Whatever the substrate, ZnO nanowires are Zn-polar, as demonstrated by convergent beam electron diffraction. For growth on O-polar ZnO substrate, the nanowires are found to sit on O-polar pyramids. As growth proceeds, the inversion domain boundary moves up in order to remain at the top of the O-polar pyramids. For growth on sapphire substrates, the nanowires may also originate from the sapphire/ZnO interface. The presence of atomic steps and the non-polar character of sapphire could be the cause of the Zn-polar crystal nucleation on sapphire, whereas it is proposed that the segregation of aluminum impurities could account for the nucleation of inverted domains for growth on O-polar ZnO.     

A review on germanium nanowires

Ge nanowires exhibit wide application potential in the fields of nanoscale devices due to their excellently optical and electrical properties. This article reviews the recent progress and patents of Ge nanowires. The recent progress and patents for the synthesis of Ge nanowires using chemical vapor deposition, laser ablation, thermal evaporation, template method and supercritical fluid-liquid-solid method are demonstrated. Amorphous germanium oxide layer and defects existing in Ge nanowires result in poor Ohmic contact between Ge nanowires and electrodes. Therefore, Ge nanowires should be passivated in order to deposit connecting electrodes before applied in nanoelectronic devices. The experimental progress and patents on the application of Ge nanowires as field effect transistors, lithium batteries, photoresistors, memory cell and fluid sensors are discussed. Finally, the future development of Ge nanowires for the synthesis and practical application is also discussed.     

Growth of straight, atomically perfect, highly metallic silicon nanowires with chiral asymmetry

In the quest of nano-objects for future electronics, silicon nanowires could possibly take over carbon nanotubes. Here we show the growth by self-organization of straight, massively parallel silicon nanowires having a width of 1.6 nm, which are atomically perfect and highly metallic conductors. Surprisingly, these silicon nanowires display a strong symmetry breaking across their widths with two chiral species that self-assemble in large left-handed and right-handed magnetic-like domains.     

Group III-nitride nanowires

Group III-nitride nanowires have attracted a lot of research interest in the past decade. They contain both the intrinsic properties of III-nitride materials and some unique properties induced by the nanowire structures. This article reviews the growth methods to obtain III-nitride nanowires, and discusses the pros and cons of both top-down and bottom-up approaches, with detailed discussions on different epitaxy methods. The most widely used catalyst-induced epitaxy and extrinsic particle free epitaxy to grow III-nitride nanowires are compared. The properties of those nanowires make them promising candidates for a broad range of applications, including optoelectronic, electronic and electromechanical devices, which are also presented, with a focus on the current challenges and recent progresses.

This review was submitted as part of the 2016 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged.     

New mode of vapor-liquid-solid nanowire growth

We report on the new mode of the vapor-liquid-solid nanowire growth with a droplet wetting the sidewalls and surrounding the nanowire rather than resting on its top. It is shown theoretically that such an unusual configuration happens when the growth is catalyzed by a lower surface energy metal. A model of a nonspherical elongated droplet shape in the wetting case is developed. Theoretical predictions are compared to the experimental data on the Ga-catalyzed growth of GaAs nanowires by molecular beam epitaxy. In particular, it is demonstrated that the experimentally observed droplet shape is indeed nonspherical. The new VLS mode has a major impact on the crystal structure of GaAs nanowires, helping to avoid the uncontrolled zinc blende-wurtzite polytylism under optimized growth conditions. Since the triple phase line nucleation is suppressed on surface energetic grounds, all nanowires acquire pure zinc blende phase along the entire length, as demonstrated by the structural studies of our GaAs nanowires.     

Ordered arrays of silicon nanowires produced by nanosphere lithography and molecular beam epitaxy

Because of their importance in fundamental research and possible applications in nanotechnology and nanoelectronics, semiconductor nanowires have attracted much interest. In addition to the growth itself, the control of the size and location is an essential problem. Here we show the growth of ordered arrays of vertically aligned silicon nanowires by molecular beam epitaxy using prepatterned arrays of gold droplets on Si(111) substrates. The ordered arrays of gold particles were produced by nanosphere lithography.     

Nanowire spintronics for storage class memories and logic

Patterned magnetic nanowires are extremely well suited for data storage and logic devices. They offer non-volatile storage, fast switching times, efficient operation and a bistable magnetic configuration that are convenient for representing digital information. Key to this is the high level of control that is possible over the position and behaviour of domain walls (DWs) in magnetic nanowires. Magnetic random access memory based on the propagation of DWs in nanowires has been released commercially, while more dynamic shift register memory and logic circuits have been demonstrated. Here, we discuss the present standing of this technology as well as reviewing some of the basic DW effects that have been observed and the underlying physics of DW motion. We also discuss the future direction of magnetic nanowire technology to look at possible developments, hurdles to overcome and what nanowire devices may appear in the future, both in classical information technology and beyond into quantum computation and biology.