Secondary electron emission from single-walled carbon nanotubes

To study secondary electron emission from single-walled carbon nanotubes and their visibility in scanning electron microscopy, their electronic structure is investigated in the presence of external electrons using first-principles calculations. By using the obtained nanotube charge density distribution, the energy loss of primary electrons as they pass through the electronic cloud of nanotube orbitals is estimated and it is shown that there could be enough energy transfer via inelastic scattering to allow the emission of secondaries. In addition, it is observed that the primary electron causes a major upward shift in occupied energy levels of the nanotube, effectively reducing the ionization energy and significantly increasing the secondary emission probability. It is also seen that if the nanotube has enough time to relax in response to the electric field of the primary electron, its ionization energy is lowered even more, further enhancing the secondary emission.