Gated Carbon Nanotube Field Emission Enhancement and Regeneration by Hydrogen
D.S.Y. Hsu and J.L. Shaw
Naval Research Laboratory, US
Keywords: field emission, field emitter array, carbon nanotube, gate structure, hydrogen
We have previously demonstrated two different configurations of integrally gated carbon nanotube field emitter arrays (FEAs). CNTs were grown inside microfabricated gate apertures with and without silicon posts. Salient features of these in-situ grown microgated cNTFEAs include the absence of electrical arcing, low operating voltage, and enhancing effect of some residual ambient gases. The motivation of the present work is to explore the regenerative and performance enhancement effects of hydrogen on field emission from carbon nanotubes, with implications to cost-savings and prolonging lifetimes of field emission devices. Previous studies reported no effect on field emission from ungated carbon nanotubes due to operation in hydrogen gas at pressure equal to or less than 10-6 Torr. Here we report large field emission enhancement for both gated configurations by operating them in hydrogen at pressures above 1 x 10-5 Torr. Depending on the initial state of nanotube contamination, enhancement factors up to 340 were obtained. Several possible factors contributing to the enhancement include H atoms forming a surface dipole (reducing the work function), hydrogen acting as an n-type dopant (increasing conductivity), and hydrogen removing oxygen-containing surface species, which may act as p-type dopants and/or increase the work function.
Nanotech 2004 Conference Technical Program Abstract