US Patent 7399215 - Carbon fiber electron emitter formed in reactive media

http://www.freepatentsonline.com/7399215.html

This patent from Canon teaches reducing the threshold voltage for electron emitting carbon fibers (e.g. carbon nanotubes) by applying a burn off voltage to the carbon fibers in a reactive atmosphere such as oxygen. Claim 1 reads:

1. A method of manufacturing an electron-emitting device, the method comprising the steps of:

preparing a first electrode having a plurality of carbon fibers;

preparing a second electrode separated, by a predetermined space, from the first electrode and also from the plurality of carbon fibers; and

applying a voltage between the first electrode and the second electrode so that a potential of the first electrode is higher than that of the second electrode,

wherein the step of applying the voltage is performed within an atmosphere containing a substance which can react with the carbon fibers.

However, there appears to be some pertinent prior art overlooked during the examination such as Wang et al. "Field emission from nanotube bundle emitters at low fields" (teaching oxygen plasma for enhancing electron emission from carbon nanotubes) and Kung et al. "Oxygen and ozone oxidation-enhanced field emission of carbon nanotubes"