Highly improved field emission properties from organic binder-free carbon nanotube emitters fabricated by a filtration-transfer technique

In this paper, we fabricated organic-free thin multi-walled CNT (thin-MWCNT) field emitters using a new filtration-transfer method. The method firstly forms the density-controlled thin-MWCNT film on a filter membrane by filtration and then transfers the film to a conductive adhesive tape. We evaluated and compared the genuine field emission properties of various CNT field emitters by using the filtration-transfer method. The average outer diameters of the double-walled CNTs, thin-MWCNTs, and thick-MWCNTs were 2.5, 7 and 25 nm, respectively, with a corresponding average tube wall number of 2, 5 and 12. The results showed that the thin-MWCNT emitter had a higher emission current density and lower turn-on field than those of thick-MWCNTs, due to the higher field enhancement factor. It is considered that thin-MWCNTs can promise various applications to field emission vacuum devices. Especially, a very high emission current density of 500 mA/cm² was obtained from thin-MWCNT emitters fabricated by the filtration-transfer method. On the other hand, the highest emission current density of sprayed emitters was only 90 mA/cm2. We consider that the high emission current of the thin-MWCNT emitter using the filtration-transfer method may be attributed to the high density of emission sites at the CNT emitter, the good electrical contact, the strong mechanical adhesion between CNTs and the cathode, and the low degradation of CNT tips. It is suggested that the filtration-transfer technique is an effective way to realize organic binder-free, low-cost, large-size and high-performance CNT emitters.