Improvement of field emission properties from screen-printed CNTs cathodes by heat treatment in a C₂H₂/H₂ gas mixture

We developed a posttreatment method for the screen-printed carbon nanotubes (CNTs) cathode to improve its field emission characteristics. The treatment was carried out at 500 °C and 20kPa for 20 min in the atmosphere of C ₂H₂/H₂ (volume ratio 1:2). After the treatment, the field emission characteristics were greatly improved. The turn-on field lowered from 5.0 to 1.6 V/μm, and the emission current density increased from 2 × 10^-4 to 1.0 mA/cm² at the electric field of 2.6 V/μm. In the mean time, the emission site density and uniformity were significantly increased. Scanning electron microscope images revealed that a new top layer of CNTs film has re-grown on the surface of the printed CNTs cathode during the treatment. This new re-grown CNTs layer contributes to the drastic enhancement of field emission from the printed cathode. This heat-treatment technique is very promising for practical application of CNTs in field emission display.