Ring formation and fracture of a carbon nanotube

An incomplete carbon ring is observed with an atomic force microscope. A possible forming mechanism of the ring is proposed in terms of ultrasonic irradiation of separate nanotube segments. The resulting ring is stabilized by the balance between the van der Waals adhesion energy and the strain energy as well as the strong interaction with the substrate. Such a mechanism is also supported by a high resolution transmission electron microscope of a carbon nanotube (CNT), an observed helix tube and a fracture process induced by an atomic force microscope.