Plasma processing based synthesis of functional nanocarbons

Our recent research has shown that plasma processing techniques, which allow versatile control of both chemical and physical aspects, have considerable potential for the innovative synthesis and functionalization of three varieties of low-dimensional nanocarbons, which show great promise in the development of nanoscience and its applications. In the case of 0-D fullerenes, the mission is the high-yield production of atom (X) encapsulated fullerenes (X@C ₆₀). The formation of macro-quantities of charge-exploited Li@C ₆₀ and overwhelmingly-high purity spin-exploited N@C₆₀ are realized for the first time by the control of alkali-fullerene and nitrogen double plasmas, respectively. In the case of 1-D carbon nanotubes the challenge is precise structure control, i.e., chirality control of single-walled carbon nanotubes (SWNTs). The extremely narrow-chirality distributed growth of SWNTs is realized with time-programmed and nonmagnetic-catalyzed plasma CVD. As for functionalization of SWNTs, the enhanced p-type C₆₀@SWNTs created under the substrate-bias control in collisionless plasmas are found to be effective for harvesting solar energy in the infrared wavelength range and adapted to the use for multiple exciton generation in solar cells. Concerning 2-D graphene, our aim is to overcome two serious issues for electronics applications. One is the realization of the direct growth of graphene on an insulating (SiO₂) substrate by adjusting the growth parameters using non-equilibrium diffusion plasma CVD. The other is the direct fabrication of field-effect transistor device of a narrow-width (≥20 nm) graphene nanoribbon using a new, simple, and scalable method based on rapid heating plasma CVD, which shows a clear transport gap and a high on/off ratio. Finally the prospects for the above-mentioned results are discussed together with ripple effects of the nanocarbon research on the progress of nanoscience and its applications.