Field emission properties of plasma treated multiwalled carbon nanotube cathode layers

Abstract

Improved field emission stability and lifetime have been observed for multiwalled carbon nanotube (MWCNT)-paste cathode layers, after plasma conditioning. Initially, MWCNT paste was synthesized and screen printed on an indium tin oxide coated glass substrate to obtain the cathode layers. These cathode layers were exposed to the Xe∕Ne plasma for a period of ∼1 or ∼3min under different biasing conditions (∼250 and ∼300V). The scanning electron microscopy micrographs, recorded for the untreated (virgin) and plasma treated cathode layers, showed significant variations in their morphology. The field emission analysis showed that the onset macroscopic field was increased from its virgin value of ∼4.65to∼9.05±0.05V∕μm for the plasma treated samples, with a subsequent decrease in the mean field-enhancement factor γav from 1251±13 to 779±43, computed from the Fowler-Nordheim plot. The variations in the current density was measured as a function of time, under low (∼10−6Torr) as well as high (∼10−8Torr) vacuum conditions, and corresponding degradation rates were computed. The degradation rate was found to be reduced by a factor of ∼103 under high vacuum conditions. The lifetime study revealed that the half-lifetime of the plasma treated samples was increased from its virgin value of ∼15to∼400h, at ∼10−6Torr. In another study, the estimated half-lifetime of the plasma treated cathode layers was found to be more than ∼20000h under high vacuum conditions (∼10−8Torr). The details of the analysis are presented.