Effects of Dielectric Barrier Discharge Treatment Conditions on the Uprightness of Carbon Nanofibers

Dielectric barrier discharge (DBD) treatment is one of the methods used to make carbon nanofibers stand up on substrates. Upright carbon nanofibers are used as field emission materials. We have used twisted carbon nanofibers (CNTws) as field emission materials and treated printed CNTws on substrates using DBD. In this report, we examine the effects of DBD conditions on the uprightness of the CNTws. The DBD experimental parameters were as follows: 1) N₂/He gas mixture ratio, 2) pulse frequency, and 3) Pt coating on the CNTw surface. The lengths of upright CNTws from the substrate surface and from the surface of a printed CNTw dot were measured using scanning electron microscopy. N₂ gas was shown to be crucial for generating streamer discharges and making the CNTw stand up on the substrate. As the pulse frequency increased, the lengths of the upright CNTws and their number density increased. This is explained by an increase in the number of streamers; the streamers move about over the substrate surface. Pt coating lowered the onset voltage for field emission from the CNTws although the number of upright CNTws was less than that without the Pt coating.