The effect of amorphous carbon layer on the field emission characteristics of carbon nanotube film

Carbon nanotube (CNT) has excellent field emission characteristics and could play as a good cold cathode in the application of vacuum electronic devices. However, the practical application faces a big obstacle regarding current fluctuation and deterioration of the CNT cathode. In this research, the formation of amorphous carbon (ac) layer between the CNT film and the substrate, and the effect of the existence of this layer on field emission stability of the CNT film are studied. The formation of the ac layer could be controlled by adjustment of growth temperature and hydrocarbon flow rate. The field emission character and current stability of the CNT film without ac layer are better than those of the CNT film with ac layer. The results attribute to the ac layer a thermal disequilibrium state under high current level. Moreover, adhesion capacity of the CNT film without ac layer is also better than that with the ac layer. It is concluded that the ac layer between the CNT film and substrate is a key factor in the stability of field emission characteristics and should be eliminated before applications.