Field emission properties of vertically aligned single- and multiwalled carbon nanotube films at temperatures up to 1000 °C are investigated by electron emission microscopy, enabling real-time imaging of electron emission to provide information on emission site density, the temporal variation of the emission intensity, and insight into the role of adsorbates. The nanotube films showed an emission site density of 104 ~ 105 cm2, which is compared to the areal density (from 1012 - 1013 cm2 to 108 - 109 cm2). At ambient temperature, the emission indicated temporal fluctuation (~6%-8%) in emission current with minimal changes in the emission pattern. At elevated temperatures, the emission site exhibited an increase in emission site intensity. From the experimental observations, it is proposed that the chemisorbed molecules tend to desorb presumably at high applied electric fields (field-induced) in combination with thermal effects (thermal-induced) and provide a contrasting comparison between semiconducting (single-walled) and metallic (multiwalled) nanotubes.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)