Laser surface treatment of carbon nanotube cathodes for field emission displays with large diagonal size

Abstract

Excimer lasers with various wavelengths, power densities and beam profiles, have been used to irradiate to carbon nanotube-cathodes (CNT-cathodes) for field emission displays (FEDs) with large diagonal size. KrF (248 nm) and XeCl (308 nm) lasers were used with average power densities varied from 3 to 9MW∕cm2. The beam shapes of the laser beam were adjusted as a square spot of 8×8mm2 for the KrF laser and a stripe of 180×0.4mm2 for XeCl laser using a beam homogenizer. The emission characteristics of CNT-cathodes were improved after laser irradiation. The turn-on-field became as low as 0.7V∕μm and the emission current density became as high as 1.5mA∕cm2 at an applied field of 2.5V∕μm by KrF laser irradiation with a power density of 4MW∕cm2. Homogeneous emission-site distribution could be obtained by a square beam or a stripe beam processing with steps from 0.2 to 0.5 mm. The emission pattern became more homogeneous with increase in laser power density. The laser processing time for large diagonal sizes using a stripe beam of 365–200×0.4mm2 have been estimated, giving a processing time of 92–138 s for a cathode of diagonal size 60 in. with an aspect ratio of 4:3.