Diameter-controlled growth of multi-walled carbon nanotubes by hot-filament chemical vapor deposition with ferritin as a catalyst on a silicon substrate

Diameter-controlled growth of multi-walled carbon nanotubes (MWNTs) has been achieved by hot-filament chemical vapor deposition with ferritin, a nano-bio-molecule, as a catalyst on a silicon substrate. Ferritin molecules are proteins containing iron oxide cores, which have a uniform diameter dependent on the ferritin size. MWNT growth was performed in a low-pressure chamber using acetylene at 540°C. In contrast to former cases, ferritin cores did not coalesce on the substrate without any additives or porous structures, due to the low growth temperature. The geometric mean diameter of the resultant MWNTs is consistent with that of iron oxide cores. It has also been found that a titanium layer on a silicon substrate assists the growth of MWNTs. The results indicate that ferritin is a good candidate catalyst for growing diameter-controlled MWNTs for electrical applications.