| Summary: | 碩士 === 國立東華大學 === 材料科學與工程學系 === 90 === Carbon nanotubes were grown by means of hot-filament chemical vapor deposition (HF-CVD) in the ambience of mixture of methane and hydrogen. Methane flowing through the hot filament was dissociated to generate carbon molecules (or clusters), and then iron and nickel transition metals were used as catalyst to facilitate the formation of then help these carbon molecules (or clusters) multi-wall carbon nanotubes (MWNTs). A scanning electron microscope (SEM) is used to observe the morphologies of the MWNTs and a Raman spectroscopy is exploited to analyze their characters.
In this study we tried to understand how the processing factors, such as DC bias power on substrate, growth time, and size and thickness of catalysts, influence the growth of MWNTs. We found that when the applied DC bias power was more than 60 watts, the MWNTs were well-aligned. In addition, the length of MWNTs was found to grow exponentially in time so that their maximum length under the optimistic conditions can be reached about 8 .
If MWNTs are grown on the arrays of Fe dots fabricated by means of e-beam lithography, by applying DC bias power supply, it enhances the amount of the growth of the carbon nanotubes (the growth density raised more than ten times). With different sizes of Fe dots, we found a critical diameter size about 40~50 nanometer with applied DC bias power supply.
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