Atomic transformations, strength, plasticity, and electron transport in strained carbon nanotubes

Abstract

Nanotubes are hollow cylinders consisting of “rolled-up” graphitic sheets. They form spontaneously in the same apparatus as the famed C60 molecule and have been predicted and/or observed to have even more spectacular properties than C60—including extremely high strength and flexibility, ability to form nanoscale electronic devices consisting entirely of carbon, strong capillary effects, and cold cathode field emission. Carbon nanotubes have also been theoretically predicted to be among the strongest materials known. Their strength, which has been verified experimentally, may enable unique applications in many critical areas of technology. While very high strain rates must lead to tube breakage, nanotubes with (n, m) indices—where n, m < 14—can display plastic flow under suitable conditions. This occurs through the conversion of four hexagons to a 5–7–7–5 defect, which then splits into two 5–7 pairs. The index of the tube changes between the 5–7 pairs, potentially leading to metal–semiconductor junctions. Carbon adatoms-induced transformations in strained nanotubes can lead to the formation of quantum dots.