The environmental stability of field emission from single-walled carbon nanotubes

Abstract

We demonstrate long-term field emission stability from single-walled carbon nanotubes. Unballasted nanotubes operate without degradation for over 350 h at 10−9 Torr. Nanotubes are shown to be significantly less sensitive to operating environments than metallic emitters. In 10−7 Torr of H2O, we demonstrate 100 h of continuous bias field emission with no current degradation. Protrusion growth and current runaway, typical problems for unballasted metal emitters, are not observed with nanotubes. Single-walled nanotubes do show susceptibility to damage by oxidation. We suggest that the exceptional environmental stability of carbon nanotubes is due to a combination of geometry, strong carbon bonding, and the lack of protrusion growth.

Effects of Cs deposition on the field-emission properties of single-walled carbon-nanotube bundles

“…The decrease is similar in magnitude to the decrease observed in the FE current from clean SWCNs during exposure to O 2 . 17 Since the FE current does not fully recover after the O 2 is removed, the decrease is attributed to damage to the SWCNs. 17 In summary, Cs deposition on SWCN bundles has a significant effect on the FE properties reducing the turn-on field by a factor of 2.1-2.8 and increasing the FE current by six orders of magnitude.…”

“…17 Since the FE current does not fully recover after the O 2 is removed, the decrease is attributed to damage to the SWCNs. 17 In summary, Cs deposition on SWCN bundles has a significant effect on the FE properties reducing the turn-on field by a factor of 2.1-2.8 and increasing the FE current by six orders of magnitude. The FE I -V curves of samples exposed to Cs show a saturation effect at large currents attributed to the Cs adsorbates.…”

Effects of oxygen adsorption on carbon nanotube field emitters

“…2 Carbon nanotubes are ideal as a field-emitting material because of their high aspect ratios and strong carbon bonding, and nanotube field emitters have been reported to achieve low-threshold voltages, large current densities, and long-term stability in the emission current. [3][4][5][6] The effects of ambient gases on the stability of the emission current are of great interest in the operation of field emitters. Especially, the influence of oxygen on the field emission has been extensively studied because oxygen constitutes a significant portion of the ambient gas and is chemically very reactive.…”

“…However, a long-term exposure to O 2 or H 2 O with a pressure higher than 10 Ϫ7 Torr resulted in an irreversible current degradation. 6,10 These puzzling effects of oxygen on the nanotube field emission have not been clearly understood yet.…”

Robust and High Current Cold Electron Source Based on Carbon Nanotube Field Emitters and Electron Multiplier Microchannel Plate

“…10 -3 -10 7 Torr. Emission of conventional metallic emitters is degraded irreversibly in low vacuum and oxygen environments because of enhanced surface reactions such as ion back sputtering, physical etching and so on [19][20][21]. Ion back sputtering and physical etching especially at the emitter tip surface degrades the local geometry and can lead to irreversible damage of the emitters.…”