Tuesday, March 11, 2008

US Patent 7341498 - Laser irradiation of CNT field emitters


Hyperion Catalysis was one of the early companies experimenting with carbon nanotubes (which they call "fibrils"). This patent teaches using laser radiation to treat carbon nanotubes so as to create more emission sites when used in field emission applications. Claim 1 reads:

1. A method of treating a field emission cathode comprising the step of irradiating a cathode with laser radiation, said cathode comprising carbon nanotubes that are substantially cylindrical having one or more graphitic layers concentric with their cylindrical axes, the nanotubes being substantially free of pyrolytically deposited carbon overcoat, having a substantially uniform diameter between 0.4 nm and 100 nm and having a length to diameter ratio greater than 5.

However, the applicant and the examiner seem to have been unaware of relevant prior art such as US Patent 6,283,812 which teaches in column 5, lines 22-26:

"According to one embodiment of the invention, reflected in FIG. 1, a high-energy beam 10 is used to truncate a ensemble of aligned nanotubes 12. Suitable beams include, but are not limited to, laser beams, electron beams, and ion beams (e.g., argon or oxygen plasma). Ion beams or plasma beams are advantageous."