In situ observations of self-repairing single-walled carbon nanotubes

Single-walled carbon nanotubes are shown to have self-repairing capabilities exceeding that predicted by theory. Time-series aberration-corrected low-voltage transmission electron microscopy is used to study the defect dynamics of single-walled carbon nanotubes in situ. We confirm experimentally previous theoretical predictions for the agglomeration of adatoms forming protrusions and subsequent ejection. An explanation for the preferred destruction of smaller-diameter tubes is proposed. The complete healing of a $\sim 20$-atom multivacancy in a nanotube wall is shown while theory only predicts the healing of much smaller holes.

Figure 1

In situ TEM observation of material ejection from a SWNT. (a) Humplike defect in the wall (see arrow), (b) formation of a protrusion, and (c) defect has disappeared. The time elapsed between each frame is 5 s.

Figure 2

(Color online) Comparison of original and simulation of a TEM image of the protrusion. (a) Fourier-filtered TEM image [cut from Fig. 1b], (b) Fourier-filtered output of a multislice simulation of the imaging process of a (14,9) tube with two three-atom protrusions, and (c) ball-and-stick illustration of the underlying molecular model for the simulation. (d) and (e) Simulation and model of a two-atom protrusion, and (f) and (g) a four-atom protrusion. Simulation parameters: accelerating voltage 80 kV, chromatic aberration 1.1 mm, spherical aberration 0.002 mm, defocus 1.8 nm, energy spread 0.8 eV, defocus spread 6.6 nm, and noise 2%.

Figure 3

In situ TEM observation of the ejection of material from a SWNT with an inner tube section formed from coalesced PCBM. (a) Material attached to the tip of an inner tube, (b) the material protruding the host wall, and (c) the host wall closed and the material has autoejected. The time elapsed between the frames is 15 s and 10 s, respectively.

Figure 4

(Color online) Time series of TEM images showing the defect dynamics of a SWNT. (a) Initial state with a defective region in the upper part (see triangle), (b) emergence of a hump in the lower part, (c) appearance of two holes in the disturbed region and a flattening out of the hump, and (d) reconstruction of the lattice in the upper part. The left wall stays undisturbed. The time elapsed from recording images (a)–(d) is 11.5 min. (e) Magnified section from rectangle in frame (c), region indicated by the box, and (f) magnified section from frame (d). (g) Fourier-filtered output of a multislice simulation of the imaging process of a (13,7) tube with a 21-atom hole, and (h) a ball-and-stick illustration of the underlying molecular model for the simulation. Simulation parameters: accelerating voltage 80 kV, chromatic aberration 1.1 mm, spherical aberration 0.002 mm, defocus 3.5 nm, energy spread 0.8 eV, defocus spread 11 nm, and noise 2%.