Growth and Density Control of Carbon Tubule Nanocoils Using Catalyst of Iron Compounds
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We synthesized carbon tubule nanocoils by catalytic thermal chemical vapor deposition. The iron catalyst necessary in the growth of carbon nanocoils was prepared only by coating the iron compound solution on indium tin oxide–coated glass substrate. It was found that the iron compounds have the same catalytic function as iron thin film prepared by evaporation or electroplating. Furthermore, the density of the prepared carbon nanocoils could be easily controlled by changing the density of the solution of iron compounds. In addition, the poly(methylphenylsilane) proved to be an excellent dispersive medium for the iron compound in preparation of the carbon nanocoils in desired densities.
I. INTRODUCTION
Carbon tubule nanocoils have attracted much attention since our report of synthesizing carbon nanocoils in high yield by catalytic thermal chemical vapor deposition (CVD).1 Due to their specula morphologies, and physical and mechanical properties,2–7 carbon nanocoils could find various applications in the field of nanotechnology, such as a spring, a generator of nano-sized magnetic beam, a high performance electromagnetic wave absorber, and an absorber of hydrogen or other gases, etc. Recently, we have found that the carbon nanocoils have uniform and stable field emission properties, which can be used to fabricate the field emitter for flat-panel display.8 The formation of coiled carbon tubules and their growth mechanism have been described by Bernaerts, Amelinckx, Zhang, and coworkers.2,3 However, these coiled tubules always grow together with a large number of nonhelical tubes. It is difficult to synthesize the coiled tubules in high yield or to control the growth density by their methods. In our system of synthesizing carbon nanocoils of high yield by CVD, it is very important to prepare the iron catalysts on indium tin oxide (ITO) films. We have used two kinds of methods to prepare iron film on ITO.1,9 One is vacuum evaporation and the other is electroplating. Both of them grow carbon nanocoils in great quantity, which are suitable for industrial fabrication. In the case of vacuum evaporation to prepare iron film, the synthesized carbon nanocoils have wide distributions of the coil diameter and pitch ranging
a)
FIG. 1. SEM micrograph of carbon nanocoils grown at the temperature of 700 °C on the substrate with the evaporated Fe film. The detail characteristics of the synthesized carbon nanocoils are described in Ref. 1.
e-mail: [email protected] J. Mater. Res., Vol. 17, No. 1, Jan 2002
http://journals.cambridge.org
from several tens to several hundreds of nanometers. In the case of electroplating to prepare the Fe film, we can obtain the carbon nanocoils with relatively narrow distributions of diameter and pitch, which are due to the sufficient mixing of iron particles to ITO films. To prepare carbon nanocoils in a desired density needed for the application to nanodevices, it is necessary to control the amount of iron deposited on the ITO substrate precisely, and sometimes this is difficult or requires
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