US Patent 7902089 - Manufacture of n-type nanotube

http://www.freepatentsonline.com/7902089.html

Carbon nanotubes tend to exhibit p-type semiconductive behavior due to adsorbed oxygen. This patent from Japanese researchers teaches a way to convert these nanotubes to n-type. Claim 1 reads:

1. A method for manufacturing a channel for an n-type transistor, wherein the method comprises:

forming a film of a nitrogenous compound directly on a nanotube-shaped structure exhibiting p-type semiconductive properties using a thermal CVD technique, at a temperature of said nanotube-shaped structure of 500° C. or higher and 1600° C. or lower; and

changing a nanotube-shaped structure exhibiting p-type semiconductive properties to said nanotube-shaped structure exhibiting n-type semiconductive properties.