An effect of argon (Ar) plasma pretreatment, followed by krypton-fluoride (KrF) laser irradiation, of multiwalled carbon-nanotube (MWCNT) cathodes on field-emission (FE) characteristics was investigated. With an Ar plasma pretreatment of 100 W, the FE current density was increased to 32.6 mA/cm(2) at an electric field of 4.92 V/mu m after laser irradiation, the value of which was about 30 times higher than the current density without plasma pretreatment. The emission-site density (ESD) was also in creased by 25 times by a plasma pretreatment of 100 W. However, the further increase in plasma power at and above 150 W deteriorated both FE characteristics and ESD, which was due to the decrease in the number of MWCNT emission sites. (c) 2007 American Vacuum Society.