Degradation of a CNT-Based Field Emission Cathode due to Ion Sputtering

The rate of degradation of carbon nanotubes (CNT) comprising a field emission cathode is calculated. The sputtering of CNT material by incident ions formed through the electron impact ionization of the residual gas molecules is considered as the degradation mechanism. The degradation rate and the relevant lifetime of CNTs have been calculated as a function of the nanotube's geometry, applied voltage, inter-electrode distance and density of the array. It has been found the abrupt dependence of the degradation rate on the applied voltage which is caused by a sharp character of the Fowler-Nordheim dependence. The dependence of the degradation rate on the inter-electrode distance is caused by the corresponding dependence of the probability of an ion to reach the CNT surface.