Field emission from nanotubes
(Top) Transmission electron microscope images of closed (left) and open multiwall nanotubes used in field-emission experiments. (Bottom) Current-voltage characteristics for field emission from open and closed nanotubes. Closed nanotubes can produce significant emission currents at much lower applied voltages than open nanotubes (J-M Bonard et al. 1999 Appl. Phys. A69 245).