Titanium oxide nanotubes were fabricated by anodic oxidation of a pure titanium sheet in an aqueous solution containing 0.5 to 3.5 wt% hydrofluoric acid. These tubes are well aligned and organized into high-density uniform arrays. While the tops of the tubes are open, the bottoms of the tubes are closed, forming a barrier layer structure similar to that of porous alumina. The average tube diameter, ranging in size from 25 to 65 nm, was found to increase with increasing anodizing voltage, while the length of the tube was found independent of anodization time. A possible growth mechanism is presented.
Aligned, open-tipped carbon nanotube arrays of high density and uniformity were synthesized via a flame method on silicon substrates using a nanoporous template of anodized aluminum oxide from which the nanotubes were grown. The diameter and length of the nanotubes are controlled by the geometry of the aluminum oxide template. These results show the feasibility of integration between carbon nanotube arrays and silicon microelectronics.
An ethylene-air laminar diffusion flame successfully provided silicon substrates of anodic aluminum oxide (AAO) template with vertically oriented well-aligned carbon nanotubes. Field emission scanning electron microscopy (SEM) showed that open-tipped carbon nanotubes consisting of tube elements with the same length and diameter uniformly coated the template. High-resolution transmission electron microscopy (TEM) analyses revealed these nanotubes to be multiwalled carbon nanotubes, some well graphitized. It was found that cobalt catalyst particles, but not the porous aluminum templates, helped the growth of carbon nanotubes through graphitization and bonding of carbon nanotubes to the silicon substrates.
Articles you may be interested inNanowelding of carbon nanotube-metal contacts: An effective way to control the Schottky barrier and performance of carbon nanotube based field effect transistors
One-dimensional Au nanoparticle arrays encapsulated within freestanding SiO nanowires are fabricated by thermal oxidation of Au-coated Si nanowires with controlled diameter and surface modulation. The nanoparticle diameter is determined by the Si nanowire diameter and Au film thickness, while the interparticle spacing is independently controlled by the Si nanowire modulation. The optical absorption of randomly oriented Au nanoparticle arrays exhibits a strong plasmonic response at 550 nm. Scanning transmission electron microscopy (STEM)-electron energy loss spectrum (EELS) of nanoparticle arrays confirmed the same plasmonic response and demonstrated uniform optical properties of the Au nanoparticles. The plasmonic response in the STEM-EELS maps is primarily confined around the vicinity of the nanoparticles. On the other hand, examination of the same nanowires by energy-filtered transmission electron microscopy also revealed significant enhancement in the plasmonic excitation in the regions in between the nanoparticles. This versatile route to synthesize one-dimensional Au nanoparticle arrays with independently tailorable nanoparticle diameter and interparticle spacing opens up opportunities to exploit enhanced design flexibility and cost-effectiveness for future plasmonic devices.
A lithography-free method for producing freestanding one-dimensional gold nanoparticle arrays encapsulated within silicon dioxide nanowires is reported. Silicon nanowires grown by the vapor-liquid-solid technique with diameters ranging from 20 nm to 50 nm were used as the synthesis template. The gold nanoparticle arrays were obtained by coating the surface of the silicon nanowires with a 10 nm gold film, followed by thermal oxidation in an oxygen ambient. It was found that the thermal oxidation rate of the silicon nanowires was significantly enhanced by the presence of the gold thin film, which fully converted the silicon into silicon dioxide. The gold-enhanced oxidation process forced the gold into the core of the wire, forming a solid gold nanowire core surrounded by a silicon dioxide shell. Subsequent thermal treatment resulted in the fragmentation of the gold nanowire into a uniformly spaced array of gold nanoparticles encapsulated by a silicon dioxide shell, which was observed by in situ annealing in transmission electron microscopy. Analysis of many different silicon nanowire diameters shows that the diameter and spacing of the gold nanopaticles follows the Rayleigh instability, which confirms this is the mechanism responsible for formation of the nanoparticle array.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.