Q. L. Hang

Amorphous silica nanowires: Intensive blue light emitters

We report large-scale synthesis of silica nanowires (SiONWs) using an excimer laser ablation method. Silica was produced in the form of amorphous nanowires at a diameter of ∼15 nm and a length up to hundreds micrometers. The SiONWs emit stable and high brightness blue light at energies of 2.65 and 3.0 eV. The intensity of the emission is two orders of magnitude higher than that of porous silicon. The SiONWs may have potential applications in high-resolution optical heads of scanning near-field optical microscope or nanointerconnections in future integrated optical devices.

Nanoscale silicon wires synthesized using simple physical evaporation

We report the large-scale synthesis of silicon nanowires (SiNWs) using a simple but effective approach. High purity SiNWs of uniform diameters around 15 nm were obtained by sublimating a hot-pressed silicon powder target at 1200 °C in a flowing carrier gas environment. The SiNWs emit stable blue light which seems unrelated to quantum confinement, but related to an amorphous overcoating layer of silicon oxide. Our approach can be used, in principle, as a general method for synthesis of other one-dimensional semiconducting, or conducting nanowires.

Growth of amorphous silicon nanowires via a solid–liquid–solid mechanism

Amorphous silicon nanowires (a-SiNW) with an average diameter of ca. 20 nm were synthesized at about 950°C under an Ar/H2 atmosphere on a large area of a (111) Si substrate without supplying any gaseous or liquid Si sources. The Si substrate, deposited with a layer of Ni (ca. 40 nm thick), served itself as a silicon source for the growth of the a-SiNWs. In contrast to the well-known vapor–liquid–solid (VLS) for conventional whisker growth, it was found that growth of the a-SiNWs was controlled by a solid–liquid–solid (SLS) mechanism, which is analogous to the VLS model.

Nano-scale GeO2 wires synthesized by physical evaporation

Abstract Germanium dioxide nanowires (GeONW) have been synthesized by a physical evaporation method. The morphology, structure and chemical composition of the wires were characterized using transmission electron microscopy (TEM) and spectroscopy of energy dispersive X-ray fluorescence (EDX). TEM observations show that the GeONWs have a very high purity and diameter ranging from 15 to 80 nm. EDX analysis reveals that the GeONWs consist of Ge and O elements. Electron diffraction patterns taken on a single GeONW are spotty patterns of single crystals and are well indexed to a GeO 2 single crystal of hexagonal structure.

Dependence of the silicon nanowire diameter on ambient pressure

Our present work provides a method to control the diameters of the silicon nanowires. As a dominant experimental parameter, the ambient pressure was controlled between 150 and 600 Torr. It is found that the average size of the silicon nanowires increases with increasing ambient pressure. The mean diameter of the silicon nanowires in our study is proportional to the 0.4 power of ambient pressure. Catalytic nanoparticles and the periodic instability of the nanowires suggest a vapor-liquid-solid growth mechanism. For the growth of nanowires, an explanation of the relationship between the mean diameter of the silicon nanowires and the ambient pressure has been proposed.

Solid–liquid–solid (SLS) growth of coaxial nanocables: silicon carbide sheathed with silicon oxide

Abstract Coaxial silicon carbide–silicon oxide nanocables on silicon substrates were synthesized from the ternary system of Si–Ni–C at 950°C under Ar/H 2 atmosphere. The nanocables consist of a hexagonal crystalline SiC core and a surface layer of amorphous silicon oxide, which have an average diameter of ∼50 nm and a length of several tens of microns. The microstructure and composition of the nanocables were characterized using high-resolution transmission electron microscope (HREM), and electron energy loss spectroscopy (EELS), and the growth mechanism of the nanocables was explained under the framework of a solid–liquid–solid (SLS) mechanism.

A Simple Method to Make Field Emitter Using Ropes of Single-Walled Carbon Nanotubes

Field emission characteristics of single-walled carbon nanotubes were studied by using a simple method in a field emission microscope. The nanotube emission gun works effectively at the room temperature under a threshold field as low as 3.9 mV/μm. A typical I-V relationship of field emission was obtained with a high current density. The observed stable bright spots on the fluorescent screen originate from an ensemble emission from micro-ropes of the single-walled carbon nanotubes.

Growth mechanism and quantum confinement effect of silicon nanowires

The methods for synthesizing one-dimensional Si nanowires with controlled diameter are introduced. The mechanism for the growth of Si nanowires and the growth model for different morphologies of Si nanowires are described, and the quantum confinement effect of the Si nanowires is presented.

Oriented Si nanowires grown via an SLS mechanism

Highly oriented silicon nanowires were grown on Si (111) substrate via a solid-liquid-solid (SLS) mechanism. Unlike the well known vapor-liquid-solid (VLS) mechanism of whisker growth, no gaseous or liquid Si source was supplied during growth. Ni was used as the liquid forming agent and mixture of H 2 and Ar was introduced in the experiment. Oriented silicon nanowires grew at 950°C and the ambient pressure kept at about 200 Torr. The oriented silicon nanowires have a length around I il m and uniform diameter about 25nm. Selected area electron diffraction showed that silicon nanowires are completely amorphous. The approach used here is simple and controllable, and may be useful in large-scale synthesis of various nanowires.

Erratum: “Nanoscale silicon wires synthesized using simple physical evaporation” [Appl. Phys. Lett. 72, 3458 (1998)]

(Received 6 October 2004; accepted 8 October 2004)[DOI: 10.1063/1.1825625]It is found recently that there was an error in two paperswe published in 1998: we mistakenly used the same XRDdata in two papers [Fig. 2(a) in Ref. 1 and Fig. 3 in Ref. 2],which described two different methods for synthesis of sili-con nanowires, whose products have the same morphologyand structure. The authors apologize for possible confusionto the readers that may have arisen from such an error,though it did not change the conclusion of the paper, becauseXRD was not the only means for structure characterization,as Raman and TEM were also used to support our conclu-sion. Moreover, our results have been repeated by our laterwork,