Field emission from nonaligned carbon nanotube-polymer matrix cathodes

We compare the field emission characteristics of multiwalled carbon nanotubes (MWNTs) and boron-doped MWNTs mixed in a polystyrene matrix. The concentration of the nanotubes was varied by weight ratio to that of the polystyrene (PS). Results indicate that the threshold fields are mainly controlled by the electric-field screening effect on the surface due to the high emission current densities measured. The lowest threshold field of 1.6 V/μm was observed from a MWNT-PS ratio of 11.1 wt %. Emission current densities, together with the threshold fields for these films, show that the emission properties are comparable to those of vertically aligned CNTs as well as arrays of carbon fibers. As the procedure to prepare these nonaligned CNT-PS composites is simple, it is proposed that the methodology could be a means of producing large area cathodes suitable for use in flat panel displays.