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Y. H. Tang

Other affiliations: University of Western Ontario
Bio: Y. H. Tang is an academic researcher from City University of Hong Kong. The author has contributed to research in topics: Nanowire & Laser ablation. The author has an hindex of 23, co-authored 30 publications receiving 3093 citations. Previous affiliations of Y. H. Tang include University of Western Ontario.

Papers
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Journal ArticleDOI
TL;DR: The lattice structure and constant of the nanowires as determined from x-ray diffraction (XRD) are nearly identical to those of bulk Si, although the relative XRD peak intensities are different from those of randomly oriented Si crystallites.
Abstract: Silicon nanowires have been synthesized in high yield and high purity by using a high-temperature laser-ablation method with growth rates ranging from 10 to 80 μm/h. Transmission electron microscopic investigation shows that the nanowires are crystalline Si, and have diameters ranging from 3 to 43 nm and length up to a few hundreds microns. Twins and stacking faults have been observed in the Si core of the nanowires. The lattice structure and constant of the nanowires as determined from x-ray diffraction (XRD) are nearly identical to those of bulk Si, although the relative XRD peak intensities are different from those of randomly oriented Si crystallites. Raman scattering from the nanowires shows an asymmetric peak at the same position as that of bulk crystalline silicon.

503 citations

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TL;DR: In this paper, a growth mechanism was proposed based on the microstructure and different morphologies of the Si nanowires observed by means of transmission electron microscopy (TEM).
Abstract: Nucleation and growth of Si nanowires by laser ablation and thermal evaporation of Si powder sources mixed with ${\mathrm{SiO}}_{2}$ have been investigated by means of transmission electron microscopy. At the initial nucleation stage, Si oxide vapor condensed on the substrate and formed Si nanoparticles (the nuclei of nanowires). Each Si nanowire nucleus consisted of a polycrystalline Si core containing a high density of defects and a Si oxide shell. A growth mechanism was proposed based on the microstructure and different morphologies of the Si nanowires observed.

292 citations

Journal ArticleDOI
TL;DR: In this paper, a bulk-quantity Si nanowires have been synthesized by thermal evaporation of a powder mixture of silicon and SiO2, and it was shown that at the initial nucleation stage, silicon monoxide vapor was generated from the powder mixture and condensed on the substrate.

274 citations

Journal ArticleDOI
TL;DR: In this article, the morphology and microstructure of the Si nanowire tips have been systematically characterized by means of high-resolution transmission electron microscopy, and the results suggest that Si oxide is more important than metal in catalyzing the formation of Si nano-connections.
Abstract: Si nanowires with uniform size have been synthesized by laser ablation of highly pure Si powder targets mixed with SiO2. A bulk quantity of Si nanowires was successfully obtained by mixing 30%–70% of SiO2 into the Si powder target. SiO2 played a crucial role in enhancing the formation and growth of the Si nanowires. The morphology and microstructure of the Si nanowire tips have been systematically characterized by means of high-resolution transmission electron microscopy. No evidence of metal was found at the tips. The results suggest that Si oxide is more important than metal in catalyzing the formation of Si nanowires.

204 citations

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TL;DR: In this article, a continuous SiNW film was prepared by grinding the pieces of sponge-like SiNWs to powder, then dispersing and sticking the powder onto a Si wafer.
Abstract: Silicon nanowires (SiNWs) were synthesized using laser ablation. A continuous SiNW film was prepared by grinding the pieces of sponge-like SiNWs to powder, then dispersing and sticking the powder onto a Si wafer. The field emission characteristics of the SiNW film were studied based on current–voltage measurements and the Fowler–Nordheim equation. The electron field emission increased with decreasing diameter of SiNWs. A hydrogen plasma treatment of the SiNW film aimed at reducing the oxide overlayer improved the emission uniformity of the film.

190 citations


Cited by
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Journal ArticleDOI
09 Mar 2001-Science
TL;DR: The beltlike morphology appears to be a distinctive and common structural characteristic for the family of semiconducting oxides with cations of different valence states and materials of distinct crystallographic structures, which could be an ideal system for fully understanding dimensionally confined transport phenomena in functional oxides.
Abstract: Ultralong beltlike (or ribbonlike) nanostructures (so-called nanobelts) were successfully synthesized for semiconducting oxides of zinc, tin, indium, cadmium, and gallium by simply evaporating the desired commercial metal oxide powders at high temperatures. The as-synthesized oxide nanobelts are pure, structurally uniform, and single crystalline, and most of them are free from defects and dislocations. They have a rectanglelike cross section with typical widths of 30 to 300 nanometers, width-to-thickness ratios of 5 to 10, and lengths of up to a few millimeters. The beltlike morphology appears to be a distinctive and common structural characteristic for the family of semiconducting oxides with cations of different valence states and materials of distinct crystallographic structures. The nanobelts could be an ideal system for fully understanding dimensionally confined transport phenomena in functional oxides and building functional devices along individual nanobelts.

5,677 citations

Journal ArticleDOI
25 Feb 2000-Science
TL;DR: Bulk quantities of defect-free silicon nanowires with nearly uniform diameters were grown to a length of several micrometers with a supercritical fluid solution-phase approach, and visible photoluminescence due to quantum confinement effects was observed, as were discrete optical transitions in the ultraviolet-visible absorbance spectra.
Abstract: Bulk quantities of defect-free silicon (Si) nanowires with nearly uniform diameters ranging from 40 to 50 angstroms were grown to a length of several micrometers with a supercritical fluid solution-phase approach. Alkanethiol-coated gold nanocrystals (25 angstroms in diameter) were used as uniform seeds to direct one-dimensional Si crystallization in a solvent heated and pressurized above its critical point. The orientation of the Si nanowires produced with this method could be controlled with reaction pressure. Visible photoluminescence due to quantum confinement effects was observed, as were discrete optical transitions in the ultraviolet-visible absorbance spectra.

1,535 citations

Journal ArticleDOI
TL;DR: In this paper, a review of porosity in on-chip wires can be found, with an attempt to give an overview of the classification, the character, and the characteristics of the porosity.
Abstract: The ever increasing requirements for electrical performance of on-chip wiring has driven three major technological advances in recent years. First, copper has replaced Aluminum as the new interconnect metal of choice, forcing also the introduction of damascene processing. Second, alternatives for SiO2 with a lower dielectric constant are being developed and introduced in main stream processing. The many new resulting materials needs to be classified in terms of their materials characteristics, evaluated in terms of their properties, and tested for process compatibility. Third, in an attempt to lower the dielectric constant even more, porosity is being introduced into these new materials. The study of processes such as plasma interactions and swelling in liquid media now becomes critical. Furthermore, pore sealing and the deposition of a thin continuous copper diffusion barrier on a porous dielectric are of prime importance. This review is an attempt to give an overview of the classification, the character...

1,496 citations

Journal ArticleDOI
TL;DR: In this article, the most recent advance in the applications of 0D (nanoparticles), 1D(nanowires and nanotubes), and 2D (thin film) silicon nanomaterials in lithium-ion batteries are summarized.
Abstract: There are growing concerns over the environmental, climate, and health impacts caused by using non-renewable fossil fuels. The utilization of green energy, including solar and wind power, is believed to be one of the most promising alternatives to support more sustainable economic growth. In this regard, lithium-ion batteries (LIBs) can play a critically important role. To further increase the energy and power densities of LIBs, silicon anodes have been intensively explored due to their high capacity, low operation potential, environmental friendliness, and high abundance. The main challenges for the practical implementation of silicon anodes, however, are the huge volume variation during lithiation and delithiation processes and the unstable solid-electrolyte interphase (SEI) films. Recently, significant breakthroughs have been achieved utilizing advanced nanotechnologies in terms of increasing cycle life and enhancing charging rate performance due partially to the excellent mechanical properties of nanomaterials, high surface area, and fast lithium and electron transportation. Here, the most recent advance in the applications of 0D (nanoparticles), 1D (nanowires and nanotubes), and 2D (thin film) silicon nanomaterials in LIBs are summarized. The synthetic routes and electrochemical performance of these Si nanomaterials, and the underlying reaction mechanisms are systematically described.

1,365 citations

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TL;DR: In this article, the authors synthesize monodisperse silicon nanowires by exploiting well-defined gold nanoclusters as catalysts for one-dimensional growth via a vapor-liquid-solid mechanism.
Abstract: Monodisperse silicon nanowires were synthesized by exploiting well-defined gold nanoclusters as catalysts for one-dimensional growth via a vapor–liquid–solid mechanism. Transmission electron microscopy studies of the materials grown from 5, 10, 20, and 30 nm nanocluster catalysts showed that the nanowires had mean diameters of 6, 12, 20, and 31 nm, respectively, and were thus well defined by the nanocluster sizes. High-resolution transmission electron microscopy demonstrated that the nanowires have single-crystal silicon cores sheathed with 1–3 nm of amorphous oxide and that the cores remain highly crystalline for diameters as small as 2 nm.

1,232 citations