Tuesday, December 19, 2006

US Patent 7148619 - Carbon Nanotube Between Two Electrodes


This patent from Canon is in the top three broadest nanotube patents I've seen (IBM's single walled nanotube patent and Till Keesman's electron emitting nanotube patent being the other two). Canon evidently thinks it invented placing a nanotube between two electrodes in 1997 (patent claims foreign priority to Oct. 30 1997). Claim 1 reads:

1. An electronic device comprising: (i) a first and a second electrodes; and (ii) a carbon nanotube electrically connecting the electrodes.

The inventor, attorney, examiner, etc. missed several pertinent technical references which I believe would clearly anticipate this and other claims of the patent. For example, in 1994 an article was published entitled "Measurements of the conductivity of individual 10 nm carbon nanotubes" by the Materials Research Society based on the proceddings of the 1994 spring meeting. The abstract of the talk is as follows:

Catalytically grown carbon fibers approximately 10 nm in diameter and several microns long were characterized by transmission electron microscopy and determined to be multiple-walled nanotubes, and a technique was developed to measure the conductivity of an individual nanotube. Nanotubes were dispersed in solvents and precipitated onto lithographically defined gold contacts to make a `nano-wire' circuit. Non-contact AFM was used to image the nano-wires, and a resistance of 11.4 (±1.0) MΩ was measured through a single nanotube at 23 °C. A resistivity of 9.5×10-5 Ωm was estimated for carbon conducting along the axis of a fiber. Local heating of nanotubes appeared to occur at high current densities. The nanotubes could sustain currents on the order of 10 μA per fiber, but application of currents on the order of 100 μA per fiber resulted in rapid decomposition in air and breaking of the circuit.

Also see "Individual single-wall carbon nanotubes as quantum wires" in Nature 386, 474 - 477 (03 April 1997)