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1.
Growth and use of metal nanocrystal assemblies on high-density silicon nanowires formed by chemical vapor deposition 总被引:1,自引:0,他引:1
A.A. Yasseri S. Sharma T.I. Kamins Z. Li R. Stanley Williams 《Applied Physics A: Materials Science & Processing》2006,82(4):659-664
In this paper, we describe the growth and potential application of metal nanocrystal assemblies on metal-catalyzed, CVD-grown
silicon nanowires (SiNWs). The nanowires are decorated by chemical assembly of closely spaced (1–5 nm) Ag (30–100 nm diameter)
and Au (5–25 nm diameter) nanocrystals formed from solutions of AgNO3 and NaAuCl4·2H2O, respectively. The formation and growth of metal nanocrystals is believed to involve the galvanic reduction of metal ions
from solution and the subsequent oxidation of available Si-hydride sites on the surfaces of the nanowires. A native oxide
layer suppresses formation of metal nanocrystals; adding HF to the ionic solutions significantly increases the density of
nanocrystals on the surfaces of the nanowires. The nanocrystals coating the nanowires were characterized by X-ray photoelectron
spectroscopy, scanning electron microscopy, and X-ray diffraction. Ag nanocrystals on the nanowires afford sensitive detection
of Rhodamine 6G (R6G) molecules in the 100 picomolar–micromolar range by surface enhanced Raman spectroscopy. In addition,
Au nanocrystals formed on selected surfaces of a substrate of arbitrary shape can serve as effective nuclei for localized
nanowire growth.
PACS 81.07.b; 81.15.Gh 相似文献
2.
Zhiwei Li Zhimei Yang Zhifeng Jiao Yanli Gao Wenyu Li Xiaosong Sun 《Applied Surface Science》2009,255(20):8571-8574
This very paper is focusing on the preparation of silver nanostructures and the surface enhanced Raman scattering effect of the silver nanostructures produced. Via electroplating technology, silver nanowires and nanoparticles were prepared on silicon wafers. Characterization was performed by X-ray diffraction, scanning electron microscope, transmission electron microscope equipped with X-ray energy dispersion spectroscope and selected area electron diffraction, which reveals that the formation of silver nanostructures depends on the over-potential. The produced silver nanowires are of crystalline FCC structure and grow in 〈0 1 1〉 direction. The growth mechanism has been further discussed. The surface enhanced Raman scattering effect is achieved with the silver nanostructures produced. 相似文献
3.
Herein we demonstrate an improved metal-assisted etching method to achieve highly dense and uniform silicon nanowire arrays. A pre-surface treatment was applied on a silicon wafer before the process of metal-assisted etching in silver nitrate and hydrogen fluoride solution. The treatment made silver ion continuously reduce on silver nuclei adherence on the silicon surface, leading to formation of dense silver nanoparticles. Silver nanoparticles acting as local redox centers cause the formation of dense silicon nanowire arrays. In contrast, an H-terminated silicon surface made silver ion reduce uniformly on the silicon surface to form silver flakes. The silicon nanowires fabricated with a pre-surface treatment reveals higher density than those fabricated without a pre-surface treatment. The volume fraction improves from 18 to 38%. This improvement reduces the solar-weighted reflectance to as low as 3.3% for silicon nanowires with a length of only 0.87 μm. In comparison, the silicon nanowires fabricated without a pre-surface treatment have to be as long as 1.812 μm to achieve the same reflectance. 相似文献
4.
5.
S. Cockcroft C. D. Walton R. Zakaria 《Applied Physics A: Materials Science & Processing》2010,100(2):379-383
We report on the laser ablation of composite prismatic structures using a vacuum ultraviolet (VUV) 157 nm F2 laser. Polycarbonate and CR-39 substrates have been intentionally seeded with silver wires and silicon carbide whiskers respectively.
The seed particles remain attached to the underlying substrate after laser ablation, forming composite silver-polycarbonate
and silicon carbide-CR-39 interfaces. Strong optical absorption at 157 nm in the polymeric substrates allows precise control
over the depth between the base of the substrate and composite interface. The surface roughness of the as-received seed particles
has a significant effect on the final surface quality of the ablated structures. The textured surface on the silicon carbide
whiskers is resolved on the walls of the ablated structures. This is in contrast to the composite structures formed using
silver wires, which have a comparatively smoother surface. 相似文献
6.
Prashant Kumar 《Journal of nanoparticle research》2010,12(7):2473-2480
In this study, we report on the trench-template assisted fabrication of nanowires for thermally evaporated indium and silicon
thin films on quartz substrate. Length of the nanowires is completely dependent on the length of the trench, whereas the diameter
of the nanowires is dependent on the thickness of the thin film. The diameter of nanowire increases from 200 nm to 1 μm when
the thickness was increased from 15 to 60 nm. It is observed that nanowires diameter is invariably controlled by material
deposition thickness. Average crystallite sizes for 60 nm indium and silicon deposition inside the trench are 120 and 35 nm,
respectively. Nanowire surface plasmon peak shift as compared to the same thickness untemplated continuous thin film is more
for thinner nanowires. This technique of nanowire fabrication is shown to be versatile in nature. 相似文献
7.
The effect of substrate roughness on growth of ultra thin diamond-like carbon (DLC) films has been studied. The ultra thin DLC films have been deposited on silicon substrates with initial surface roughness of 0.15, 0.46 and 1.08 nm using a filted cathodic vacuum arc (FCVA) system. The films were characterized by Raman spectroscope, transmission electron microscope (TEM) and atomic force microscopy (AFM) to investigate the evolution of the surface roughness as a function of the film thickness. The experimental results show that the evolution of the surface morphology in an atomic scale depends on the initial surface morphology of the silicon substrate. For smooth silicon substrate (initial surface roughness of 0.15 nm), the surface roughness decreased with DLC thickness. However, for silicon substrate with initial surface roughness of 0.46 and 1.08 nm, the film surface roughness decreased first and then increased to a maximum and subsequently decreased again. The preferred growth of the valley and the island growth of DLC were employed to interpret the influence of substrate morphology on the evolution of DLC film roughness. 相似文献
8.
Yunsen Zhang Donglai Liu Xue Bai Huabing Song Wenyu Li Xiaosong Sun 《Journal of luminescence》2010,130(6):1005-1473
This very paper is focusing on the investigation of porous silicon preparation with n-type silicon wafer by means of electrochemical anodization in the dark and, particularly, on its stable ultraviolet photoluminescence emission. A lateral electrical potential was applied, for this purpose, on silicon wafers, driving the electrons away and letting holes appear on the surface of the silicon wafer to enhance the electrochemical etching process. Characterizations have been made with scanning electronic microscope, fluorescence spectrophotometer and Fourier transform infrared spectroscope. An ultraviolet photoluminescence emission of 370 nm is found in the as-prepared n-type porous silicon, which seems to be well associated with the formation of oxygen-related species (twofold coordinated silicon defect) during the anodic oxidation. The result characterized by photo-bleaching performance indicates that the ultraviolet photoluminescence emission is so stable—only 7% reduction within 3600 s. Meanwhile the morphology of as-prepared n-type porous silicon is investigated. 相似文献
9.
X. C. Jiang S. X. Xiong C. Y. Chen W. M. Chen A. B. Yu 《Journal of nanoparticle research》2011,13(10):5087-5101
This study demonstrates a facile but effective polyol-thermal reaction method for the synthesis of silver nanowires in autoclaves
(160–180 °C). By this approach, the generated silver nanowires show an average diameter of ~40 nm and length up to tens of
micrometers with a high yield and potential for large-scale production. To achieve shape- and size-controlled Ag nanowires,
several experimental parameters were investigated and optimized, including surface controller(s), molar ratio of surfactant(s)
to silver ions, temperature, and concentration of reactants. The structure and composition of silver nanowires were characterized
by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), and X-ray diffraction
(XRD) techniques. In particular, the twinned crystal structure observed in both spherical particles and nanowires was analyzed
by HRTEM technique, and the possible formation and growth mechanisms were discussed. The optical property of the as-prepared
product was measured by ultraviolet–visible (UV–vis) spectroscopy. The sensing detection of metal ions (e.g., Hg2+) using the obtained silver nanowires in aqueous media was finally investigated. 相似文献
10.
Xiaodong Zhou Kai Yu Liu Nan Zhang Dong-Hwan Kim Christina Tan 《Journal of nanoparticle research》2011,13(7):2919-2927
Dispersing nanospheres on a large glass substrate is the key to fabricate noble metal nanostructures for localized surface
plasmon resonance through dispersed nanosphere lithography. This article reports that by modifying the glass surface with
low dose ion implantation and successively dip coating the surface with poly(diallyldimethyl ammonium chloride) (PDDA), polystyrene
or silica nanospheres can be dispersed on a large glass substrate. Investigation shows that several kinds of ions, such as
silicon, boron, argon, and arsenic, can improve the nanosphere dispersion on glass, attributed to the ion bombardment-caused
silicon increment. Ion implantation imposes no surface roughness or optical loss to the glass substrate, thus this method
is suitable for localized surface plasmon resonance application. Experiments show silicon ion implantation can best disperse
the nanospheres. For the gold nanostructures obtained by obliquely evaporating 30 nm of gold film onto the polystyrene nanospheres,
which are dispersed on a silicon ion implanted glass substrate, a localized surface plasmon resonance sensitivity of 242 nm/RIU
is achieved. 相似文献
11.
R.A. Zhachuk 《Surface science》2004,565(1):37-44
The ordered arrays of Ag nanowires and nanodots have been grown in ultra-high vacuum on the Si(5 5 7) surface containing regular steps of three bilayer height. Formation of Ag nanostructures have been studied by scanning tunneling microscopy, low energy electron diffraction and Auger electron spectroscopy at room temperature. It was shown that a sample exposure in the vacuum before Ag growth affects the shape of the forming Ag islands. This effect is caused by oxygen adsorption on the silicon surface from the residual atmosphere in the vacuum chamber. When Ag is deposited on the clean silicon surface the islands, overlapping several (1 1 1) neighboring terraces, form. The arrays of silver nanowires elongated along steps and silver nanodots, arranged in lines parallel to the steps, can be formed on the Si(5 5 7) surface depending on the amount of adsorbed oxygen. 相似文献
12.
Yuming Liu 《Solid State Communications》2005,133(2):131-134
Carbon nanotubes are synthesized on the silicon nanowire arrays which are fabricated on silicon substrate by chemical vapor depositing SiCl4 and H2 gases in the presence of Au catalysts. The silicon nanowires are single-crystal with lengths up to 100 μm and diameters ranging from 50 to 500 nm. The tangled carbon nanotubes are grown directly from the surface of Si nanowires. The field emission properties of the carbon nanotubes are investigated at the gap of 200 μm. The low turn on and threshold fields are obtained. The stabilization of the emission currents is also presented. 相似文献
13.
Golovan LA Gonchar KA Osminkina LA Timoshenko VY Petrov GI Yakovlev VV 《Laser physics letters》2012,9(2):145-150
In this letter, we, for the first time, report on coherent anti-Stokes Raman scattering (CARS) spectroscopy of an ensemble of silicon nanowires (SiNWs) formed by wet chemical etching of crystalline silicon with a mask of silver nanoparticles. The fabricated SiNWs have diameter ranged from 30 to 200 nm and demonstrate both visible and infrared photolumine cence (PL) and spontaneous Raman signal, with their intensities depending on presence of silver nanoparticles in SiNWs. The efficiency of CARS in SiNW ensembles is found to be significantly higher than that in crystalline silicon. The results of CARS and PL measurements are explained in terms of resonant excitation of the electron states attributed to silicon nanoparticles. 相似文献
14.
Sword-like (diameter ranging from 40 nm to 300 nm) and needle-like zinc oxide (ZnO) nanostructures (average tip diameter ∼40 nm)
were synthesized on annealed silver template over silicon substrate and directly on silicon wafer, respectively via thermal
evaporation of metallic zinc followed by a thermal annealing in air. The surface morphology, microstructure, chemical analysis
and optical properties of the grown samples were investigated by field emission scanning electron microscopy, X-ray diffraction,
energy dispersive X-ray analysis, room temperature photoluminescence and Raman spectroscopy. The sword-like ZnO nanostructures
grown on annealed silver template are of high optical quality compared to needle-like ZnO nanorods for UV emission and show
enhanced Raman scattering. 相似文献
15.
Silver nanoparticles have been formed on the surface of lead crystal glass by means of (i) ion-exchange of alkaline ions from the glass by Ag+ ions from a molten salts bath, and (ii) silica based sol-gel coatings containing silver. All experimental variables concerning both ion-exchange process and sol-gel coatings application were combined and studied as main parameters governing the reduction of Ag+ ions to Ag0 atoms and further aggregation to form nanosized colloids. The content of thermoreducing agents (arsenic or antimony oxides) in the lead crystal glass was essential to favour the reduction of silver ions to form nanoparticles. Optimal experimental conditions to be used for the obtaining of surface silver nanoparticles were determined. TEM was used as the principal characterisation technique for direct observation of the nanoparticles generated. The size of silver colloids varied in the 20-300 nm range for ion-exchanged samples and in the 10-80 nm range for sol-gel coated samples. 相似文献
16.
Nanosphere lithography (NSL) is a successful technique for fabricating highly ordered arrays of ZnO nanowires typically on sapphire and GaN substrates. In this work, we investigate the use of thin ZnO films deposited on Si by pulsed laser deposition (PLD) as the substrate. This has a number of advantages over the alternatives above, including cost and potential scalability of production and it removes any issue of inadvertent n-type doping of nanowires by diffusion from the substrate. We demonstrate ordered arrays of ZnO nanowires, on ZnO-coated substrates by PLD, using a conventional NSL technique with gold as the catalyst. The nanowires were produced by vapor phase transport (VPT) growth in a tube furnace system and grew only on the areas pre-patterned by Au. We have also investigated the growth of ZnO nanowires using ZnO catalyst points deposited by PLD through an NSL mask on a bare silicon substrate. 相似文献
17.
High purity n-type silicon single crystal with resistivity in the order of 4000 Ω cm has been irradiated with high-energy oxygen ions at room temperature up to a fluence of 5E15 ions/cm2. The energy of the beam was varied from 3 to 140 MeV using a rotating degrader to achieve a depthwise near-uniform implantation profile. Radiation induced defects and their dynamics have been studied using positron annihilation spectroscopy along with isochronal annealing up to 700 °C in steps of 50 °C for 30 min. After annealing the sample at 200 °C for 30 min, formation of silicon tetravacancies has been noticed. The formation of the tetravacancies was found to be due to agglomeration of divacancies present in the irradiated sample. An experimentally obtained positron lifetime value of 338±10 ps has been reported for silicon tetravacancies, which has a very close agreement with the value obtained from recent theoretical calculations. The tetravacancies were found to dissociate into trivacancy clusters upon further annealing. The trivacancies thus obtained were observed to agglomerate beyond 400 °C to form larger defect clusters. Finally, all the defects were found to anneal out after annealing the sample at 650 °C. 相似文献
18.
Nanodendrites consisting of silver and silver oxide are grown upon a pulsed-laser induced reaction at the interface between the solid target and silver nitrate solution. By using a high-resolution transmission electron microscope (HRTEM) equipped with an energy dispersive X-ray spectrometer (EDS) and selected area diffraction (SAD), the fabricated nanopatterns are identified to be a composite structure that consisting of silver nanoparticles and silver oxide nanoplumes with polycrystalline structure. In detail, these silver nanocrystals are trunks of the nanodendrite, and their size is in the range of 30 to 50 nm. The silver oxide nanoplumes are branches of the nanodendrite, and their width and length are in the ranges of 20 to 50 nm and 30 to 100 nm, respectively. Additionally, we suggested a vapor-liquid mechanism for the formation of the nanopatterns using a pulsed-laser induced liquid-solid interface reaction, in which both silver clusters in vapor and silver ions in solution are simultaneously involved.Received: 6 April 2004, Published online: 5 November 2004PACS:
81.15.Fg Laser deposition - 61.46. + w Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals - 81.07.Bc Nanocrystalline materials 相似文献
19.
Christiane Erler 《Applied Surface Science》2009,255(24):9647-9651
We report the synthesis of metallic nanowires accomplished by site-specific integration of single DNA duplexes into micro-fabricated contact arrays and their subsequent selective metallization. DNA interconnects between metallic contacts are formed by tethering the ends of DNA molecules, stretched in hydrodynamic flow into a linear conformation, at different gold contact pads via thiol functional groups. To transform the DNA interconnects into metallic cluster chains or nanowires, we use an electroless metal deposition technique where platinum ions bound along the DNA molecules from a salt solution are reduced to metallic clusters of less than 10 nm in diameter by applying UV light. 相似文献
20.
Silicon nanowires (SiNWs) were prepared by the electrochemical reduction of solid Ni/SiO2 blocks in molten CaCl2 at 1173 K. The SiNWs have diameter distributions ranging from 80 to 350 nm, and the nickel–silicon droplets are found on the tips of the nanowires. The growth mechanism of SiNWs was investigated, which confirmed that the nano-sized nickel–silicon droplets formed at the Ni/SiO2/CaCl2 three-phase interline. The droplets lead to the oriented growth of SiNWs. Formation of nano-sized nickel–silicon droplets suggests that this method could be a potential way to produce nano-sized metal silicides. 相似文献