Imaging of carbon nanostructures by low energy STEM below 5 keV

Our work deals with the imaging of nanostructures composed of light biogenic elements, such as carbon nanotubes, by low energy scanning transmission electron microscopy (STEM). Compared to imaging at the voltages commonly used for TEM and STEM, low energy electrons seem very promising in terms of specimen damage that is caused by a number of elastic andn inelastic collisions. In carbonaceous materials, the most problematic is probably the knock-on damage, where the structure can be impaired by carbon atom displacement. To avoid this problem with structures composed of light elements, a reduction in beam voltage going down to 5 keV has recently been proposed. The range below 5 keV has not been explored yet for this purpose, although electron scattering in matter is lower for these energies, which allows achieving a higher spatial resolution. We aim to demonstrate that additional reduction of incident electron energy may yield interesting contrast features