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1.
Investigation of the growth process of Si nanowires using the vapour-liquid-solid mechanism
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Silicon nanowires have been grown by the thermal decomposition of silane via the vapour-liquid-solid (VLS) mechanism. Three different stages of VLS growth (eutectic alloy formation, crystal nucleation and unidirectional growth) were studied separately using a scanning electron microscope and a high-resolution transmission electron microscope. Very short silicon nanowires prepared under particular conditions provide direct evidence of the VLS mechanism on a nanometre scale. Our results will be very helpful for the controllable synthesis of Si nanowires. 相似文献
2.
Sawtooth faceting in silicon nanowires 总被引:1,自引:0,他引:1
We observe in situ the vapor-liquid-solid (VLS) growth of Si nanowires, in UHV-CVD using Au catalyst. The nanowire sidewalls exhibit periodic sawtooth faceting, reflecting an oscillatory growth process. We interpret the facet alternation as resulting from the interplay of the geometry and surface energies of the wire and liquid droplet. Such faceting may be present in any VLS growth system in which there are no stable orientations parallel to the growth direction. The sawtooth structure has important implications for electronic mobility and scattering in nanowire devices. 相似文献
3.
We report the structural and morphological properties of well-aligned ZnO nanowires grown at 750 °C on Au-deposited and annealed
(100)Si substrates using carbo-thermal evaporation. As-grown nanowires are made of wurtzite ZnO, have cylindrical shape and
carry droplet-like nanoparticles (NPs) at their tips, as expected for vapour–liquid–solid (VLS) growth. Grazing incidence
X-ray diffraction measurements demonstrate that the NPs are made of pure fcc Au. No secondary Au/Zn alloy phases were detected.
Bragg diffraction patterns confirmed that the nanowires were grown with their crystal c-axes parallel to the [100] direction
of Si (i.e. normal to the substrate surface), while Au NPs are mostly (111)-oriented. The diameter distribution of ZnO nanowires
mimics that of the Au NPs at their tips. A quantitative study of the nanostructure size distribution after sequential annealing
and growth steps evidences the occurrence of three nanoscale processes: (i) Ostwald ripening and/or coalescence of Au NPs
before nanowire nucleation, (ii) Au-catalysed VLS nucleation and axial growth of ZnO nanowires and (iii) radial growth of
nanowires by a vapour–solid process. These processes originate the NP and nanowire size evolution during the experiments.
The present findings are interpreted in terms of Zn vapour pressure changes during carbo-thermal evaporation.
PACS 61.46.+w; 68.65.-k; 81.16.Dn 相似文献
4.
采用化学气相沉积系统制备ZnO纳米线,以覆盖一层约5nm厚的Ag薄膜的单晶Si(001)为衬底,纳米线的生长遵循气-液-固(VLS)机理。对得到的样品采用X射线衍射(XRD)和扫描电镜(SEM)进行晶体结构和形貌的表征。XRD结果表明衬底温度在600~700℃时生长的ZnO纳米线具有六方结构和统一的取向。通过扫描电子显微镜分析,比较了生长温度对纳米线直径和长度的影响。实验表明我们可以通过催化剂和温度来实现ZnO纳米线生长的可控。与传统的VLS生长方式不同的是在我们制备的ZnO纳米线顶端并没有看到催化剂颗粒,表明纳米线的生长方式是底部生长,我们对其生长机理进行了研究。 相似文献
5.
Recent experiments by Ross and co-workers proved the possibility of a mononuclear regime with heterogeneous nucleation as well as jerky growth in the vapor–liquid–solid (VLS) process for silicon nanowires. In this work, a theoretical model is presented which incorporates the effects of (i) a mononuclear regime with layer by layer growth, (i) heterogeneous nucleation of each new layer at the edge of a Au–Si droplet, (iii) drop of supersaturation after each successful nucleation and respective fast layer growth, (iv) time-dependent nucleation barrier during each new waiting period and (v) correlation between subsequent waiting periods (non-Markovian sequence of waiting periods). 相似文献
6.
Single-crystalline Sb-doped Ge nanowires (NWs) with excellent structural properties and uniform composition have been synthesized
with high yield by vapor–liquid–solid (VLS) growth by low-temperature thermal evaporation from a mixture of Ge and Sb powders.
During deposition, both the Ge and the Sb dopant became incorporated in the VLS seed nanoparticle. In situ annealing experiments
during transmission electron microscopy establish that a liquid ternary Au-Sb-Ge alloy constitutes the active phase of the
VLS seed drop at high temperatures, which governs the growth of the one-dimensional Ge NW and its doping by Sb. 相似文献
7.
Long silicon nanowires (SiNWs) grown by laser ablation or by thermal evaporation of monoxide source materials are primarily
oriented in the <112> direction, and some in the <110> direction, but rarely in the <100> or <111> directions. We propose
a model to explain these SiNW growth directional features. The model consists of two parts. Part one is concerned with mechanism-based
criteria and part two with applying these criteria to explain the experimental results. Four criteria are considered: (i)
the stability of a Si atom occupying a surface site; (ii) the Si {111} surface stability in the presence of oxygen; (iii)
the stepped Si {111} surface layer lateral growth process; and (iv) the effect of dislocations in providing perpetuating {111}
steps to facilitate SiNW growth. Analyses of SiNW growth in accordance with these criteria showed that <112> and <110> are
the preferred SiNW growth directions, and that <111> and <100> are not.
Received: 12 November 2001 / Accepted: 20 November 2001 / Published online: 23 January 2002 相似文献
8.
S. Sharma T.I. Kamins R. Stanley Williams 《Applied Physics A: Materials Science & Processing》2005,80(6):1225-1229
Silicon nanowires were synthesized using chemical vapor deposition catalyzed by gold nanoparticles deposited on silicon substrates. Silicon nanowires grew epitaxially in 111 directions on (100)-oriented silicon substrates. For a particular set of process parameters, we observed a critical thickness of the nucleating gold film, below which nanowires could not be grown. We studied the dependence of the Au-Si alloy droplet size and size distribution on the starting gold film thickness and the annealing conditions. Increasing the Cl:Si ratio in the gas phase allowed nanowires to grow on smaller Au-Si alloy droplets. We used a modified heating sequence that deconvoluted the effect of silicon substrate consumption and gas-phase silicon supply on the Au-Si alloy formation and allowed growth of nanowires with diameters less than 20 nm. The modified heating sequence was also used to demonstrate the growth of bridging silicon nanowires with diameters less than 20 nm, which is a significant step in producing electronic devices. PACS 81.07.b; 81.15.Gh 相似文献
9.
Maryam RoozbehiParvaneh Sangpour Ali KhademiAlireza Z. Moshfegh 《Applied Surface Science》2011,257(8):3291-3297
The ZnO nanowires have been synthesized using vapor-liquid-solid (VLS) process on Au catalyst thin film deposited on different substrates including Si(1 0 0), epi-Si(1 0 0), quartz and alumina. The influence of surface roughness of different substrates and two different environments (Ar + H2 and N2) on formation of ZnO nanostructures was investigated. According to AFM observations, the degree of surface roughness of the different substrates is an important factor to form Au islands for growing ZnO nanostructures (nanowires and nanobelts) with different diameters and lengths. Si substrate (without epi-taxy layer) was found that is the best substrate among Si (with epi-taxy layer), alumina and quartz, for the growth of ZnO nanowires with the uniformly small diameter. Scanning electron microscopy (SEM) reveals that different nanostructures including nanobelts, nanowires and microplates have been synthesized depending on types of substrates and gas flow. Observation by transmission electron microscopy (TEM) reveals that the nanostructures are grown by VLS mechanism. The field emission properties of ZnO nanowires grown on the Si(1 0 0) substrate, in various vacuum gaps, were characterized in a UHV chamber at room temperature. Field emission (FE) characterization shows that the turn-on field and the field enhancement factor (β) decrease and increases, respectively, when the vacuum gap (d) increase from 100 to 300 μm. The turn-on emission field and the enhancement factor of ZnO nanowires are found 10 V/μm and 1183 at the vacuum gap of 300 μm. 相似文献
10.
The un-doped and boron-doped silicon nanowires (SiNWs) were grown via vapor–liquid–solid (VLS) mechanism by low pressure chemical
deposition (LPCVD). The diameters of un-doped and boron-doped SiNWs varied from 18.5 to 75.3 nm and 26.6 to 66.1 nm, respectively.
The critical growth temperature of boron-doped SiNWs is 10°C lower than that of un-doped ones and the diameters of the boron-doped
SiNWs is always larger than that of the un-doped ones under different growth temperatures. This is because that the introduction
of diborane enhanced the dissociation of SiH4 which determines the growth process of SiNW. A growth process of silicon nanowire is proposed to describe the influence of
B2H6. 相似文献
11.
Jun Beom Park Nam-Jung Kim Yong-Jin Kim Sang-Hyup Lee Gyu-Chul Yi 《Current Applied Physics》2014,14(11):1437-1442
We report the growth of high-areal-density GaN nanowires on large-size graphene films using a nickel (Ni) catalyst-assisted vapor-liquid-solid (VLS) method. Before the nanowire growth, the graphene films were prepared on copper foils using hot-wall chemical vapor deposition and transferred onto SiO2/Si substrates. Then, for catalyst-assisted VLS growth, Ni catalyst layers with thickness of a few nanometers were deposited on the graphene-coated substrates using a thermal evaporator. We investigated the effect of the Ni catalyst thickness on the formation of GaN nanowires. Furthermore, the structural and optical characteristics of GaN nanowires were investigated using X-ray diffraction, transmission electron microscopy, and photoluminescence spectroscopy. The GaN nanowires grown on graphene films were transferred onto polymer substrates using a simple lift-off method for applications as flexible photocatalysts. Photocatalysis activities of the GaN nanowires prepared on the flexible polymer substrates were investigated under bending conditions. 相似文献
12.
用SnO和Zn的均匀混合物在高温下共烧通过VLS机制制备出孪晶ZnO纳米线的均匀结构。SEM图像显示孪晶ZnO纳米线的直径在100~200nm之间,长度在几十微米到几百微米之间的范围内,有的甚至达到了毫米级,产率也非常的高。TEM图像中ZnO孪晶纳米线顶端的金属Sn颗粒表明了孪晶结构的Sn催化生长。高分辨电子图谱显示了氧化锌纳米线孪晶结构的特征。电子衍射分析发现孪晶氧化锌的晶带轴的方向是[0110],孪晶面为(1013),并且通过明场像和暗场像分析了孪晶纳米线的晶格关系,确定了孪晶纳米线的汽-液-固(VLS)生长机制。 相似文献
13.
Mohamed Benaissa Jacques Werckmann Gabrielle Ehret Jean Guille Eric Peschiera 《Interface Science》1993,1(2):91-98
SiC whiskers were grown from the reaction of silicon monoxide (SiO) with activated carbon containing iron impurities. Growth proceeds through a VLS growth mechanism with SiO and CO as reacting gases. HRTEM combined with EDS shows that the SiC whisker is topped by a Fe3Si catalyst droplet. The SiC whisker is found to be one-dimensionally disordered along the [111] growth direction of an fcc crystal structure. Although the catalyst droplet is usually larger than the top face of the whisker, we observed a number of situations where the diameter of the droplet was smaller. The study of the SiC-Fe3Si interface showed that the growth is nucleated from the edges. 相似文献
14.
D. Tham C.-Y. Nam K. Byon J. Kim J.E. Fischer 《Applied Physics A: Materials Science & Processing》2006,85(3):227-231
We review our current progress on semiconductor nanowires of β-Ga2O3, Si and GaN. These nanowires were grown using both vapor–solid (VS) and vapor–liquid–solid (VLS) mechanisms. Using transmission electron microscopy (TEM) we studied their morphological, compositional and structural characteristics. Here we survey the general morphologies, growth directions and a variety of defect structures found in our samples. We also outline a method to determine the nanowire growth direction using TEM, and present an overview of device fabrication and assembly methods developed using these nanowires. PACS 61.14.-x; 81.07.-b; 61.14.Lj; 81.05.-t 相似文献
15.
通过化学气相沉积法在不同衬底上制备了大量的氧化硅纳米线.选用衬底为Si片、带有约100nm厚SiO2氧化层Si片和石英片.利用场发射扫描电子显微镜(SEM)和透射电镜(TEM,配备有能谱仪)对样品的表面形貌、结构和成分进行研究.结果表明:这些纳米线都为非晶态,但在不同衬底上生长的纳米线形貌、尺寸和化学成分不同.讨论了各种衬底对不同特征氧化硅纳米线生长的影响.
关键词:
化学气相沉积
纳米线
纳米颗粒 相似文献
16.
It was demonstrated that the etching in HF-based aqueous solution containing AgNO3 and Na2S2O8 as oxidizing agents or by Au-assisted electroless etching in HF/H2O2 solution at 50 °C yields films composed of aligned Si nanowire (SiNW). SiNW of diameters ∼10 nm were formed. The morphology and the photoluminescence (PL) of the etched layer as a function of etching solution composition were studied. The SiNW layers formed on silicon were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and photoluminescence. It was demonstrated that the morphology and the photoluminescence of the etched layers strongly depends on the type of etching solution. Finally, a discussion on the formation process of the silicon nanowires is presented. 相似文献
17.
Dae Hoon KwonHyeun Hwan An Hee-Soo KimJong Ho Lee Sang Hee SuhYoung Ho Kim Chong Seung Yoon 《Applied Surface Science》2011,257(10):4650-4654
Si nanowires (SiNWs) were modified by Au nanoparticles (AuNPs) using a self-assembled monolayer of aminopropyltriethoxysilane (APTES) and used for direct sensing of the bovine serum albumin (BSA). It was shown that repeated thermal treatment of the sensor greatly enhanced the reliability of the SiNW sensor by increasing the electrical conductivity largely from carbonization of the APTES molecules and from bringing the AuNPs in intimate contact with the SiNW surface. The AuNP-modified SiNW array sensor was able to detect 1-7 μM of BSA. The sensor exhibited a good sensitivity over the tested concentration range and linear behavior. It is expected that the proposed label-free biosensor can be further developed to selectively detect and quantify biomolecules other than BSA. 相似文献
18.
Jens Bauer Ullrich Pietsch Anton Davydok Andreas Biermanns J?rg Grenzer Volker Gottschalch Gerald Wagner 《Applied Physics A: Materials Science & Processing》2009,96(4):851-859
The heteroepitaxial growth process of InAs nanowires (NW) on GaAs $[\bar{1}\bar{1}\bar{1}]_{\mathrm{B}}$ substrate was investigated by X-ray grazing-incidence diffraction using synchrotron radiation. For crystal growth we applied the vapor–liquid–solid (VLS) growth mechanism via gold seeds. The general sample structure was extracted from various electron microscopic and X-ray diffraction experiments. We found a closed Ga x In1?x As graduated alloy layer at the substrate to NW interface which was formed in the initial stage of VLS growth with a Au–Ga–In liquid alloy. With ongoing growth time a transition from this VLS layer growth to the conventional VLS NW growth was observed. The structural properties of both VLS grown crystal types were examined. Furthermore, we discuss the VLS layer growth process. 相似文献
19.
Ki-Hong Lee Charles Lofton Won-Seon Seo Myung-Hyun Lee 《Solid State Communications》2004,131(11):687-692
Photoluminescence characteristics of amorphous silica nanowires (a-SiONWs) grown on TiN/Ni/Si and TiN/Ni/SiO2 substrates have been studied. A-SiONWs grown on TiN/Ni/Si substrates show a Si-rich composition compared to those grown from TiN/Ni/SiO2/Si. The emission characteristics of the nanowires were found to depend on the type of substrate. By annealing the a-SiONWs grown on TiN/Ni/Si in air, emission bands shift from blue to green bands. It is likely that silicon to oxygen ratio is an important factor in deciding the types of defects and emission bands of amorphous silica nanowires. 相似文献
20.
Optical activation of patterned Si nanowires grown from sol-gel prepared gold/Er-doped aluminous film is investigated. The growth of patterned Si nanowires (SiNWs), the doping of Er ions and the sintered process are completed by one step. Si nanowires were grown from a sol-gel solution containing both Au catalysts and Er ions by the vapor-liquid-solid method. Such Er-activated Si nanowires achieve both high carrier-mediated excitation efficiency and high Er luminescence efficiency while at the same time providing high areal density of Er and easy current injection, indicating the possibility of activated patterned Si nanowires grown from sol-gel film as a material platform for Si-based photonics. 相似文献