The influence of adsorption desorption processes on the work function of the cathode made of carbon nanotubes

The possibility of field emission cathodes of carbon nanotubes to operate during thousands of hours under technical vacuum conditions were described in some works. In this work, interesting phenomenon on the significant degradation of cathodes of carbon nanotubes during hours of operation was obtained. Experimental measurements of the electron work function of the cathode were conducted by the mean of the FN-chats. The longtime field emission tests were conducted at the current stabilization mode. According to the obtained data it's possible to draw a conclusions about the presence of two periods with different reasons of the degradation. The first degradation period corresponds the cathode work function changing. The work function changes due to destruction of the adsorbed molecules under ion bombardment. The second one corresponds to decreasing the emission area or number of nanotubes.