FIG. 4. (a) Tunneling current vs sample voltage curve for the carbon nano- tube with diameter of 2.O nm, showing linear behavior about o V indicating a metallic density of states. (b) Tunneling current vs sample voltage curve for the metallic HOPG substrate showing linear behavior about o indicat- ing a metallic density of states. graphite layers(the interlayer distance in graphite being 3-4 A) Figure 3(d) shows a line scan taken between the two arrows near region A in Fig. 30a)- The line scan clearly shows the graphene sheet structure. Graphene sheets have been conjectured to be produced during the arc discharge, but have not yet been reported. These thin structures lying on the surface would be difficult to observe using TEM, but would easily be observed using STM which is highly sensi- tive to surface topography In conclusion, we have used STM and STM I-P curves to study the structural and electronic properties of individual carbon nanotubes Our results show that nanotubes with di ameters from 2 to 5.1 nm have a metallic DOS.