Interpretation of the {100} fringes in lattice images from the centre of carbon nanotubes

Abstract

The lattice image for the centre of a carbon nanotube is sensitive to variations in the parameters of the tube such as the helical angle, the cross-sectional shape and the crystal tilt. We have obtained HREM images of tubes which show (002) fringes at the edges of the tube and {100} fringes in the centre. From these images we have deduced much useful information about the structure of the tubes. Simulations of the {100} fringes for a typical carbon nanotube demonstrate the sensitivity of the image to differences in helical pitch, large angles of crystal tilt and the presence of amorphous carbon in the centre of the tube. Small crystal tilts and random translational disorder between the shells are shown to have little effect on the image. The expected variations in the images as a function of cross-sectional shape are discussed.