Controlled growth of vertically aligned carbon nanofibers by plasma enhanced chemical vapor deposition

We investigated the growth behavior and morphology of vertically aligned carbon nanofibers (CNFs) grown on silicon (Si) substrates by using dc plasma enhanced chemical vapor deposition. We found that plasma etching and electric-field direction played important roles in controlling the CNF morphology and alignment direction, respectively. Si etching and resulting redeposition often produced tapered diameter carbon nanocones containing Si. Deposition of protection layers, such as Ti, TiN, and W, successfully suppressed the unwanted etching and enabled desirable needle-like CNF growth. In a conventional field emitter structure, a gate metal layer, surrounding a CNF emission tip, could be utilized as a protection layer to allow cylindrical CNF growth. We also demonstrated that sharply bent CNFs could be grown by manipulating the electric-field direction. This growth of sharply bent CNFs clearly manifests the electric-field-induced CNF alignment mechanism and that mechanism can be applied to other nanostructure syntheses.