Effects of micro- and macro-plasma-sheath electric fields on carbon nanotube growth in a cross-field radio-frequency discharge

Effects of magnetic-field introduction and micro∕macroelectric fields in a plasma sheath on the carbon nanotube growth are investigated by employing a cylindrical magnetron-type radio-frequency (rf) plasma-enhanced chemical-vapor deposition method. The cross-field magnetic-field application is accompanied by the high-density plasma generation and the reduction of direct impinge of high-energy ions to a rf electrode substrate, achieving the carbon nanotube formation without harmful sputtering phenomenon. It is found that microelectric fields in the plasma sheath are useful in the sense of substrate pretreatment and macroelectric fields have to be optimized in order to obtain well-aligned and refined nanotube structures in a large area. These experimental results lead to putting into practice of quite simple methods for the site-selected carbon nanotube growth in a relatively large area, so-called substrate-scratching method and mesh-masking method.