Influence of gas atmosphere during laser surface treatment of CNT cathode

The I-V characteristics of carbon nanotube (CNT) cathodes after laser irradiation in air, N/sub 2/ and O/sub 2/ atmospheres have been compared to investigate the influence of each component of air. The I-V characteristic of CNT cathodes irradiated in O/sub 2/ was drastically improved, while there was almost no improvement in I-V characteristics irradiated in N/sub 2/. The O/sub 2/ pressure dependence during laser irradiation to CNT cathodes was also examined. The emission current density at an applied field of 6.6 V//spl mu/m was increased by a factor of 200 for laser irradiation in air. The emission current was enhanced by a factor of 400 for laser irradiation in 10/sup 5/ Pa of O/sub 2/ and the number of emission sites was drastically increased. The emission current density increased with an increase in pressure. The mechanism for drastic improvement in electron emission by UV laser irradiation is via laser-induced oxidation.