Optimization of field emission properties from multi-walled carbon nanotubes using ceramic fillers

The field emission properties of multi-walled carbon nanotubes were examined using a screen-printed thick film with a diode-type configuration in a vacuum. The effects of various concentrations of two different ceramic fillers, indium tin oxide (ITO) powder and a glass frit, on the emission current density and turn-on field were evaluated. The emission properties of both pastes were dependent on the amount of filler. Considerably enhanced emission properties were obtained with the paste containing 5–10 wt.% of either ITO or the glass frit compared with those without a filler. The paste containing the ceramic filler showed enhanced emission properties compared with that containing the 5 wt.% Ag conventionally used, which confirmed the importance of the filler. The paste containing 10 wt.% ITO represented an emission current density of 176.4 μA/cm² at 5 V/μA, a turn-on field of 1.87 V/μA for an emission current density of 1 μA/cm² and a field enhancement factor of 7580. The paste formulation was also found to be suitable for fine patterning using UV-lithography techniques. A long-term stability test for 110 h of a paste containing 10 wt.% ITO revealed a half-life of approximately 30000 h, which is appropriate for commercial applications.