Degradation of a carbon nanotube-based field-emission cathode during ion sputtering

The degradation rate of carbon nanotubes (CNTs) in an electron field emitter is calculated. The degradation mechanism is taken to be the sputtering of the CNT surface by the ions that result from the ionization of residual gas molecules by an electron impact. The degradation rate and the corresponding CNT lifetime are calculated as a function of the nanotube geometry, the applied voltage, the pressure and kind of a residual gas, the interelectrode gap, and the nanotube array density. The obtained strong dependence of the degradation rate on the applied voltage is caused by a sharp character of the I?CV emission characteristic determined by the Fowler-Nordheim relationship. The dependence of the degradation rate on the interelectrode gap is induced by the corresponding dependence of the probability of reaching the CNT surface.