Electron emission characteristics of carbon nanotube cathodes with and without reactive ion etching (RIE) followed by KrF laser irradiation were investigated. The emission characteristics of samples without RIE process, such as emission current density, turn-on field, and emission pattern, strongly depend on the laser power density, which is caused by a photon process at low laser power densities of 2-4 MW/cm(2) and a thermal ablation at high power densities of 10-14 MW/cm(2). The emission characteristics of samples with RIE, however, show little change when the laser power density is varied. Surface morphologies of CNT cathodes with RIE process show little change by laser treatment compared to the case of CNT cathodes without RIE process. (c) 2007 American Vacuum Society.