Stable multiwalled carbon nanotube electron emitter operating in low vacuum

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Abstract
We have investigated field emission (FE) properties of an individual multiwalled carbon nanotube (CNT) under low‐vacuum regions around 10 −3 Pa. Current versus voltage characteristics of the present CNT emitters were found to be explicable on the basis of the Fowler–Nordheim (F–N) formalism. Time trace of the FE current exhibited more than 30% fluctuation about the mean value, and the lifetime was less than 5 h. Scanning electron microscopy (SEM) observation elucidated that the lengths of the CNTs were reduced after prolonged field emission, plausibly because of local heating induced by the large current density at the apex. To prolong the lifetime, we attempted a type of feedback system by inserting a high ohmic resistance between the electron emitter and the power supply. As a result, the current fluctuation decreased from ∼30% to 2% at 0.1 µA, and the lifetime increased from 5 to 50 h. Finally, an SEM was equipped with both the emitter systems, with and without resistance, which were designed for the CNT field emitter. The SEM images taken by using the emitter with resistance showed consistently brighter appearance, whereas those taken without the resistance exhibited fluctuations in the image brightness. Copyright © 2006 John Wiley & Sons, Ltd.

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