Carbon nanotubes as elements to focus electron beams by Fresnel diffraction

Fresnel diffraction of electrons at curved edges can be used to focus electrons onto a spot when the concave side of the edge is transparent. It is shown that short multi-wall carbon nanotubes with diameters of the inner hollow core of a few nanometers act as electron focusers when they are aligned parallel to the beam in an electron microscope. The electron beam is focused onto the projected center of the tube, where an amplification of the electron intensity by several times can be attained. (C) 2003 American Institute of Physics.