Laser surface treatment of CNT cathodes for large diagonal FEDs

High power laser irradiation with a stripe beam is the key technology for large diagonal carbon nanotube (CNT) cathode surface treatment. CNT cathodes were fabricated on ITO/glass substrates by screen-printing with conventional organic binder. Screen-printed CNT cathodes were irradiated by KrF (248 nm) and XeCl (308 nm) excimer lasers. The spot shape was adjusted as a spot of 8×8 mm² or a stripe of 200×0.4 mm². The stripe beam was irradiated in a step of 0.2, 0.3, 0.4, 0.5 and 0.8 mm. The emission characteristics were measured in a vacuum chamber with a pressure of 10-5 Pa. The emission patterns on a phosphor screen were observed by a CCD camera. The turn-on-field became the lowest with a step of 0.5 mm. The turn-on-field became as low as 0.7 V/μm and the emission density became as high as 1.5 mA/cm² at a field of 2.5 V/μm by KrF laser irradiation.