Individual carbon nanotubes were filled with fullerene molecules directly on a substrate. Two different oxidation techniques for opening tubes prior to filling, annealing in air, and acid treatment, were compared. High-resolution transmission electron microscopic images indicated that both methods introduced defects into the side-walls of the nanotubes. In the case of acid treatment, the inner walls could be damaged without affecting the outer walls, while the inner walls were opened together with the outer ones by heating in air. The effect of acid treatment upon the tubes was much stronger than known from bulk samples. In contrast to previous studies, amorphous carbon was found inside the nanotubes after oxidation, and an additional high-temperature annealing step was needed to remove these plugs in order to open the tubes for filling.

Defects Induced on Chemical Vapour Deposition Carbon Nanotubes during Peapod Synthesis on Substrates. C.Meyer, C.Spudat, L.Houben, C.M.Schneider: Nanotechnology, 2009, 20[6], 065603