Carbon Nanotubes Grown on Metallic Wires by Cold Plasma Technique
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Carbon Nanotubes Grown on Metallic Wires by Cold Plasma Technique D. Sarangi and A. Karimi Institute of Physics of the Complex Materials (IPMC-FSB), Swiss Federal Institute of Technology (EPFL), CH 1015 Lausanne, Switzerland.
ABSTRACT
Carbon nanotubes on metallic wires may be act as electrode for the field emission (FE) luminescent devices. Growing nanotubes on metallic wires with controlled density, length and alignment are challenging issues for this kind of devices. We, in the present investigation grow carbon nanotubes directly on the metal wires by a powerful but simple technique. A novel approach has been proposed to align nanotubes during growth. Methane, acetylene and dimethylamine have been used as source gases. With the same growth conditions (viz. pressure, growth temperature and plasma) methane does not produce any nanotube but nanotubes grown with dimethylamine show shorter length and radius than acetylene. The effect of temperature to control the radius, time to control the density, plasma conditions to align the nanotubes has been focused. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Rutherford Back Scattering (RBS) are used to characterize the nanotubes.
INTRODUCTION
After the decade of the discovery of the carbon nanotubes (CNTs) [1], they have generated extensive interest among the research community due to their unique properties and potential applications [2]. The excellent emission properties of the nanotubes allow one to realize the use of the nanotube-coated wire as a cathode of the luminescent tube, which is mercury-free and may be the alternatives of the fluorescent tubes [3]. But for practical realization, controlled and wellaligned growth of the nanotubes is essential. Control placing or patterning of the nanotubes over the flat surface is not new. Large number of techniques like soft lithography [4], micro-contact printing (µCP) [5] are available. Growing of nanotubes over irregular substrates like metallic wires is rarely available. We, in this paper, report the growth of nanotubes on metallic wires by a very simple technique and also propose the way to align the nanotubes. We show that nanotubes grow very fast and the growth temperature has the effect not only on the diameter of the nanotubes but also on the periodicity of the spiral nanotubes as grown.
EXPERIMENTAL DETAILS
We have used Kanthal (0.3 mm diameter, Fe-Al-Cr alloy) wire to grow nanotubes. At first, the wires were oxidized by heating above 1000oC in air for several minutes. Fe catalyst was coated on the surface of the wire by dipping it in an ethanolic solution of 40 mM iron nitrate,
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Fe(NO3)3 9H2O. The wire was inserted into the vacuum chamber and screwed between two isolated electrodes. The chamber was then evacuated to a pressure of about 10-6 mbar. Hydrocarbon gases like methane (CH4) or acetylene (C2H2) or dimethylamine (C2H7N) was aspirated into the chamber by a high precision mass flow controller to keep the chamber pressure around 15 mbar. Carbon nanotubes we
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