Enhancement of electron emission and long-term stability of tip-type carbon nanotube field emitters via lithium coating

Abstract

Carbon nanotubes (CNTs) were deposited on conical tip-type substrates via electrophoresis and coated with lithium( Li) thin films with diverse thicknesses via electroplating. For the as-deposited (i.e., without Li coating) CNT, the turn-on (or triggering) electric field was 0.92 V/mu m, and the emission current, which was generated at an applied field of 1.2 V/mu m was 56 mu A. In the case of the 4.7 nm-thick Li-coated CNT, the turn-on field decreased to 0.65 V/mu m and the emission current at the same applied field increased more than ten times to 618 mu A. The analysis based on the Kelvin probe measurement and Fowler-Nordheim theory indicated that the coating of Li caused a loss in the structural-aspect-ratio of the CNTs and it reduced their effective work functions from 5.36 eV to 4.90 eV, which led to a great improvement of their electron emission characteristics. The results obtained in this study also showed that the long-term emission stability could be enhanced by the coating of thin Li films on CNTs. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.