AVS 50th International Symposium
    Nanotubes Thursday Sessions
       Session NT-ThM

Paper NT-ThM1
Analyses of Early Stages of Vertically Aligned Carbon Nanotube Growth

Thursday, November 6, 2003, 8:20 am, Room 317

Session: Nanotube Growth and Processing
Presenter: Y. Hayashi, Kyoto Institute of Technology, Japan
Authors: Y. Hayashi, Kyoto Institute of Technology, Japan
K. Ueda, Kyoto Institute of Technology, Japan
Y. Watanabe, Kyoto Institute of Technology, Japan
S. Nishino, Kyoto Institute of Technology, Japan
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Vertically aligned carbon nanotubes are expected to be used for the electron emitters of a field emission display, which demands large-area and low-voltage operation. We have developed the method of large-area growth of well-aligned carbon nanotubes by hot-filament assisted dc plasma chemical vapor deposition (HF/DC-P CVD).@footnote 1,2@ In order to obtain high electron emission density at low voltage, the crystallinity and alignment of carbon nanotubes should be controlled. However the growing mechanisms of aligned carbon nanotubes, especially early stages, have not well been understood. Therefore we are analyzing substrate surface states in the early states of aligned carbon nanotube growth in HF/DC-P CVD by in-situ ellipsometry along with other ex-situ analytical methods. The ellipsometer is a rotating-analyzer type and the light source is a diode laser of the wavelength of 690 nm. Carbon nanotubes were grown on an iron film about 500 nm thick in the DC plasma of 20 % methane diluted in hydrogen after the pretreatment in a pure hydrogen plasma. The trajectory of ellipsometric parameters in the early stages was compared with that of simulation which was performed using the effective medium approximation for the calculation of the optical indexes of a film equivalent to aligned carbon nanotubes of a certain diameter and density. From the results of the ellipsometry and SEM observation, it was found that an incubation period of about 2 min exists before the growth of carbon nanotubes and the carbonization of iron fine particles, which were formed during the pretreatment process, was occurred in the incubation period. @FootnoteText@@footnote 1@Y.Hayashi , T.Negishi, and S.Nishino, J. Vac. Sci. Technol. A 19 (2001) 1796. @footnote 2@K.Ueda, T.Negishi, Y.Hayashi and S.Nishino, in preparation for publication.