US Patent 7357691 - Flat CNT field emission array

http://www.freepatentsonline.com/7357691.html

This patent discloses an interesting method for making carbon nanotube vertical array field emitters. Usually the nanotubes are grown from a cathode electrode but in this method the cathode electrode is formed on top of the nanotubes after growth and the supporting substrate from which the nanotubes are grown is removed. This method provides uniform length nanotube arrays with a flat surface. Claim 1 reads:

1. A method for making a carbon nanotube-based field emission device comprising steps of:

providing a substrate having a flat surface which has a variation in flatness of less than 1 micron;

forming a carbon nanotube array extending from a selected area of the surface of the substrate by a chemical vapor deposition process, the carbon nanotube array having a flat bottom surface corresponding to the flat surface of the substrate; forming a cathode electrode on a top of the carbon nanotube array; and

removing the substrate so as to expose the flat bottom surface of the carbon nanotube array so that the flat bottom surface of the carbon nanotube array is thereby configured for acting as an electron emitting surface of the carbon nanotube-based field emission device.