Jamie H.Warner, Neil P. Young, Angus I. Kirkland and G. Andrew D. Briggs, Resolving strain in carbon nanotubes at the atomic level, Nature Materials, Vol 10, Dec 2011- (Oxford University)
Understanding the mechanical properties of nanomaterials at the atomic-scale is of great importance for their utilization in nanoelectromechanical systems (NEMS), especially in light of the recent observation of quantum phenomena on the macroscopic scale. Suspended SWNTs, with their remarkably high tensile strengths and elasticity, are ideal oscillators for NEMS and predicting their resonant frequency characteristics accurately requires the incorporation of shear strain, such as in the Timoshenko beam model, or possibly even non-local strain models.
The incorporation of aberration correctors into transmission electron microscopes has opened up a new field in performing atomic-resolution microscopy at low accelerating voltages. This has been revolutionary for carbon nanomaterials, where a low accelerating voltage of 80 kV is needed to reduce knock-on damage to sp2 carbon nanomaterials such as SWNTs, graphene, fullerenes and peapods. The ability to resolve carbon lattice structure with high-resolution transmission electron microscopy (HRTEM) enables information to be determined that reveals defects, holes and layer stacking in graphene. In carbon nanotubes HRTEM has been used to determine the chirality of SWNTs and double-walled carbon nanotubes as well as see lattice defects.
Until now there has been a lack of experimental evidence regarding how the atomic structure of a carbon nanotube changes under strain from bending. For large bending angles, buckling of the SWNT is observed. However in most cases SWNTs are well below their buckling limit and only slightly distorted in their shape. Resolving strain at the atomic level is at the forefront of structural characterization using aberration-corrected HRTEM.