Tuesday, January 15, 2008

US Patent 7318763 - Fabrication of metallized nanotube array


This patent from General Electric teaches a CVD method of forming field emission devices by metallizing carbon nanotubes. Claim 1 reads:

1. A method of making a metallized carbon nanostructure, comprising the steps of: a. placing at least one carbon nanostructure formed on a substrate in a furnace; and b. applying a metallic vapor to the carbon nanostructure at a preselected temperature for a preselected period of time so that the metallic vapor reacts with carbon nanostructure to form a metallized nanostructure including a solid core about the carbon nanostructure.

However, the patent examiner may have missed some relevant prior art such as US Patent 6,504,292
(http://www.freepatentsonline.com/6504292.html ) which teaches regarding the formation of metallized carbon nanotube field emitters:

"As shown in FIGS. 3 ( a ) to 3 ( c ), the metal coating 5 can be applied by different known techniques of physical vapor deposition such as sputtering, evaporation or ion beam process, chemical vapor deposition by decomposing metal-containing precursor gas, or electrochemical deposition such as electroless or electrolytic coating. The desired average thickness of the metal film coating on nanostructures, such as carbon nanotubes, and on the substrate is in the range of 0.2-100 nanometer, and preferably in the range of 0.5-20 nanometers. The metal coating 5 does not necessarily have to cover 100% of the surface of the nanostructures 1 or the substrate 2 , as long as continuous paths for electrical conduction along the length is provided to most of the emitting tips 3 . For the purpose of exceeding the percolation limit for continuity of the conducting path, the surface area coverage by the metallic coating is desirably at least about 30%, although a much lower fraction of area coverage is also acceptable if the metal deposition pattern is anisotropic, e.g., with at least ˜5%. In the case of line-of-sight metal deposition such as sputtering, evaporation or ion-beam deposition, the substrate may be rotated, if desired, to overcome the shadowing effect, to ensure sufficient area coverage and to provide symmetry. The result is an assembly 9 of metallized nanostructures on a metallized substrate. "