In SituObservation of Thermal Relaxation of Interstitial-Vacancy Pair Defects in a Graphite Gap

Abstract

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