RESISTANCE VS. PRESSURE OF SINGLE-WALL CARBON NANOTUBES

The electrical resistance of single-wall carbon nanotubes (SWNT) produ ced by condensation of a laser-vaporized graphite/Ni/Co mixture at 120 0 degrees C was studied under quasihydrostatic pressures up to 90 kbar . The resistance exhibits a positive temperature coefficient, characte ristic of a metal, up to 10 kbar, whereas the absolute value decreases abruptly by a factor approximate to 10. From 10-30 kbar R increases w ith pressure and the TCR becomes negative. At still higher pressure, u p to 90 kbar, R decreases gradually with pressure, similar to the case of graphite. Raman scattering and electron microscopy performed after 25-kbar pressurizations indicate that the SWNT and its lattice are pr eserved. We propose that the sequential behavior of R(P) reveals in tu rn the processes of compaction, defect formation by kinking, and final ly the van der Waals compression of the inter-tube spacing in the tria ngular lattice.