Direct observation of individual defects during formation and annihilation in the interlayer gap of double-wall C nanotubes was demonstrated by high-resolution transmission electron microscopy. The interlayer defects that bridge two adjacent graphene layers in double-wall C nanotubes were stable for a macroscopic time at below 450K. These defects were assigned to a cluster of one or two interstitial-vacancy pairs (I-V pairs) and often disappear just after their formation at higher temperatures due to an instantaneous recombination of the interstitial atom with a vacancy. Systematic observations performed at the elevated temperatures find a threshold for the defect annihilation at 450-500K, which, indeed, corresponds to the known temperature for the Wigner energy release.

In situ Observation of Thermal Relaxation of Interstitial-Vacancy Pair Defects in a Graphite Gap. K.Urita, K.Suenaga, T.Sugai, H.Shinohara, S.Iijima: Physical Review Letters, 2005, 94[15], 155502 (3pp)