INVESTIGATIONS OF CARBON NANOTUBES

Experiments have been carried out to optimize the yields of carbon nan otubes obtained by the arc-evaporation of graphite. Other types of car bon particles such as nanocrystalline graphite usually present along w ith the nanotubes are readily removed by heating the material in oxyge n around 763 K. Clean nanotubes so obtained have been characterized by X-ray diffraction. The clean tubes are thermally more stable than gra phite or fullerenes. The tips of carbon nanotubes are opened by reacti on with oxygen, but more interestingly, when the oxygen produced by th e decomposition of a metal oxide is used to open the tube tips, the me tal formed in the process enters the nanotube. Electrical resistance o f pressed pellets of clean tubes is not unlike that of graphite. Tunne lling conductance measurements on isolated tubes characterized by mean s of scanning tunnelling microscopy however show that the conductance gap increases with decreasing tube diameter.